The ALSA Driver API

Management of Cards and Devices

Card Management

void snd_device_initialize(struct device * dev, struct snd_card * card)

Initialize struct device for sound devices

Parameters

struct device * dev
device to initialize
struct snd_card * card
card to assign, optional
int snd_card_new(struct device * parent, int idx, const char * xid, struct module * module, int extra_size, struct snd_card ** card_ret)

create and initialize a soundcard structure

Parameters

struct device * parent
the parent device object
int idx
card index (address) [0 ... (SNDRV_CARDS-1)]
const char * xid
card identification (ASCII string)
struct module * module
top level module for locking
int extra_size
allocate this extra size after the main soundcard structure
struct snd_card ** card_ret
the pointer to store the created card instance

Description

Creates and initializes a soundcard structure.

The function allocates snd_card instance via kzalloc with the given space for the driver to use freely. The allocated struct is stored in the given card_ret pointer.

Return

Zero if successful or a negative error code.

int snd_card_disconnect(struct snd_card * card)

disconnect all APIs from the file-operations (user space)

Parameters

struct snd_card * card
soundcard structure

Description

Disconnects all APIs from the file-operations (user space).

Return

Zero, otherwise a negative error code.

Note

The current implementation replaces all active file->f_op with special
dummy file operations (they do nothing except release).
int snd_card_free_when_closed(struct snd_card * card)

Disconnect the card, free it later eventually

Parameters

struct snd_card * card
soundcard structure

Description

Unlike snd_card_free(), this function doesn’t try to release the card resource immediately, but tries to disconnect at first. When the card is still in use, the function returns before freeing the resources. The card resources will be freed when the refcount gets to zero.

int snd_card_free(struct snd_card * card)

frees given soundcard structure

Parameters

struct snd_card * card
soundcard structure

Description

This function releases the soundcard structure and the all assigned devices automatically. That is, you don’t have to release the devices by yourself.

This function waits until the all resources are properly released.

Return

Zero. Frees all associated devices and frees the control interface associated to given soundcard.

void snd_card_set_id(struct snd_card * card, const char * nid)

set card identification name

Parameters

struct snd_card * card
soundcard structure
const char * nid
new identification string

Description

This function sets the card identification and checks for name collisions.
int snd_card_add_dev_attr(struct snd_card * card, const struct attribute_group * group)

Append a new sysfs attribute group to card

Parameters

struct snd_card * card
card instance
const struct attribute_group * group
attribute group to append
int snd_card_register(struct snd_card * card)

register the soundcard

Parameters

struct snd_card * card
soundcard structure

Description

This function registers all the devices assigned to the soundcard. Until calling this, the ALSA control interface is blocked from the external accesses. Thus, you should call this function at the end of the initialization of the card.

Return

Zero otherwise a negative error code if the registration failed.

int snd_component_add(struct snd_card * card, const char * component)

add a component string

Parameters

struct snd_card * card
soundcard structure
const char * component
the component id string

Description

This function adds the component id string to the supported list. The component can be referred from the alsa-lib.

Return

Zero otherwise a negative error code.

int snd_card_file_add(struct snd_card * card, struct file * file)

add the file to the file list of the card

Parameters

struct snd_card * card
soundcard structure
struct file * file
file pointer

Description

This function adds the file to the file linked-list of the card. This linked-list is used to keep tracking the connection state, and to avoid the release of busy resources by hotplug.

Return

zero or a negative error code.

int snd_card_file_remove(struct snd_card * card, struct file * file)

remove the file from the file list

Parameters

struct snd_card * card
soundcard structure
struct file * file
file pointer

Description

This function removes the file formerly added to the card via snd_card_file_add() function. If all files are removed and snd_card_free_when_closed() was called beforehand, it processes the pending release of resources.

Return

Zero or a negative error code.

int snd_power_wait(struct snd_card * card, unsigned int power_state)

wait until the power-state is changed.

Parameters

struct snd_card * card
soundcard structure
unsigned int power_state
expected power state

Description

Waits until the power-state is changed.

Return

Zero if successful, or a negative error code.

Note

the power lock must be active before call.

Device Components

int snd_device_new(struct snd_card * card, enum snd_device_type type, void * device_data, struct snd_device_ops * ops)

create an ALSA device component

Parameters

struct snd_card * card
the card instance
enum snd_device_type type
the device type, SNDRV_DEV_XXX
void * device_data
the data pointer of this device
struct snd_device_ops * ops
the operator table

Description

Creates a new device component for the given data pointer. The device will be assigned to the card and managed together by the card.

The data pointer plays a role as the identifier, too, so the pointer address must be unique and unchanged.

Return

Zero if successful, or a negative error code on failure.

void snd_device_disconnect(struct snd_card * card, void * device_data)

disconnect the device

Parameters

struct snd_card * card
the card instance
void * device_data
the data pointer to disconnect

Description

Turns the device into the disconnection state, invoking dev_disconnect callback, if the device was already registered.

Usually called from snd_card_disconnect().

Return

Zero if successful, or a negative error code on failure or if the device not found.

void snd_device_free(struct snd_card * card, void * device_data)

release the device from the card

Parameters

struct snd_card * card
the card instance
void * device_data
the data pointer to release

Description

Removes the device from the list on the card and invokes the callbacks, dev_disconnect and dev_free, corresponding to the state. Then release the device.

int snd_device_register(struct snd_card * card, void * device_data)

register the device

Parameters

struct snd_card * card
the card instance
void * device_data
the data pointer to register

Description

Registers the device which was already created via snd_device_new(). Usually this is called from snd_card_register(), but it can be called later if any new devices are created after invocation of snd_card_register().

Return

Zero if successful, or a negative error code on failure or if the device not found.

Module requests and Device File Entries

void snd_request_card(int card)

try to load the card module

Parameters

int card
the card number

Description

Tries to load the module “snd-card-X” for the given card number via request_module. Returns immediately if already loaded.

void * snd_lookup_minor_data(unsigned int minor, int type)

get user data of a registered device

Parameters

unsigned int minor
the minor number
int type
device type (SNDRV_DEVICE_TYPE_XXX)

Description

Checks that a minor device with the specified type is registered, and returns its user data pointer.

This function increments the reference counter of the card instance if an associated instance with the given minor number and type is found. The caller must call snd_card_unref() appropriately later.

Return

The user data pointer if the specified device is found. NULL otherwise.

int snd_register_device(int type, struct snd_card * card, int dev, const struct file_operations * f_ops, void * private_data, struct device * device)

Register the ALSA device file for the card

Parameters

int type
the device type, SNDRV_DEVICE_TYPE_XXX
struct snd_card * card
the card instance
int dev
the device index
const struct file_operations * f_ops
the file operations
void * private_data
user pointer for f_ops->:c:func:open()
struct device * device
the device to register

Description

Registers an ALSA device file for the given card. The operators have to be set in reg parameter.

Return

Zero if successful, or a negative error code on failure.

int snd_unregister_device(struct device * dev)

unregister the device on the given card

Parameters

struct device * dev
the device instance

Description

Unregisters the device file already registered via snd_register_device().

Return

Zero if successful, or a negative error code on failure.

Memory Management Helpers

int copy_to_user_fromio(void __user * dst, const volatile void __iomem * src, size_t count)

copy data from mmio-space to user-space

Parameters

void __user * dst
the destination pointer on user-space
const volatile void __iomem * src
the source pointer on mmio
size_t count
the data size to copy in bytes

Description

Copies the data from mmio-space to user-space.

Return

Zero if successful, or non-zero on failure.

int copy_from_user_toio(volatile void __iomem * dst, const void __user * src, size_t count)

copy data from user-space to mmio-space

Parameters

volatile void __iomem * dst
the destination pointer on mmio-space
const void __user * src
the source pointer on user-space
size_t count
the data size to copy in bytes

Description

Copies the data from user-space to mmio-space.

Return

Zero if successful, or non-zero on failure.

void * snd_malloc_pages(size_t size, gfp_t gfp_flags)

allocate pages with the given size

Parameters

size_t size
the size to allocate in bytes
gfp_t gfp_flags
the allocation conditions, GFP_XXX

Description

Allocates the physically contiguous pages with the given size.

Return

The pointer of the buffer, or NULL if no enough memory.

void snd_free_pages(void * ptr, size_t size)

release the pages

Parameters

void * ptr
the buffer pointer to release
size_t size
the allocated buffer size

Description

Releases the buffer allocated via snd_malloc_pages().

int snd_dma_alloc_pages(int type, struct device * device, size_t size, struct snd_dma_buffer * dmab)

allocate the buffer area according to the given type

Parameters

int type
the DMA buffer type
struct device * device
the device pointer
size_t size
the buffer size to allocate
struct snd_dma_buffer * dmab
buffer allocation record to store the allocated data

Description

Calls the memory-allocator function for the corresponding buffer type.

Return

Zero if the buffer with the given size is allocated successfully, otherwise a negative value on error.

int snd_dma_alloc_pages_fallback(int type, struct device * device, size_t size, struct snd_dma_buffer * dmab)

allocate the buffer area according to the given type with fallback

Parameters

int type
the DMA buffer type
struct device * device
the device pointer
size_t size
the buffer size to allocate
struct snd_dma_buffer * dmab
buffer allocation record to store the allocated data

Description

Calls the memory-allocator function for the corresponding buffer type. When no space is left, this function reduces the size and tries to allocate again. The size actually allocated is stored in res_size argument.

Return

Zero if the buffer with the given size is allocated successfully, otherwise a negative value on error.

void snd_dma_free_pages(struct snd_dma_buffer * dmab)

release the allocated buffer

Parameters

struct snd_dma_buffer * dmab
the buffer allocation record to release

Description

Releases the allocated buffer via snd_dma_alloc_pages().

PCM API

PCM Core

const char * snd_pcm_format_name(snd_pcm_format_t format)

Return a name string for the given PCM format

Parameters

snd_pcm_format_t format
PCM format
int snd_pcm_new_stream(struct snd_pcm * pcm, int stream, int substream_count)

create a new PCM stream

Parameters

struct snd_pcm * pcm
the pcm instance
int stream
the stream direction, SNDRV_PCM_STREAM_XXX
int substream_count
the number of substreams

Description

Creates a new stream for the pcm. The corresponding stream on the pcm must have been empty before calling this, i.e. zero must be given to the argument of snd_pcm_new().

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_new(struct snd_card * card, const char * id, int device, int playback_count, int capture_count, struct snd_pcm ** rpcm)

create a new PCM instance

Parameters

struct snd_card * card
the card instance
const char * id
the id string
int device
the device index (zero based)
int playback_count
the number of substreams for playback
int capture_count
the number of substreams for capture
struct snd_pcm ** rpcm
the pointer to store the new pcm instance

Description

Creates a new PCM instance.

The pcm operators have to be set afterwards to the new instance via snd_pcm_set_ops().

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_new_internal(struct snd_card * card, const char * id, int device, int playback_count, int capture_count, struct snd_pcm ** rpcm)

create a new internal PCM instance

Parameters

struct snd_card * card
the card instance
const char * id
the id string
int device
the device index (zero based - shared with normal PCMs)
int playback_count
the number of substreams for playback
int capture_count
the number of substreams for capture
struct snd_pcm ** rpcm
the pointer to store the new pcm instance

Description

Creates a new internal PCM instance with no userspace device or procfs entries. This is used by ASoC Back End PCMs in order to create a PCM that will only be used internally by kernel drivers. i.e. it cannot be opened by userspace. It provides existing ASoC components drivers with a substream and access to any private data.

The pcm operators have to be set afterwards to the new instance via snd_pcm_set_ops().

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_notify(struct snd_pcm_notify * notify, int nfree)

Add/remove the notify list

Parameters

struct snd_pcm_notify * notify
PCM notify list
int nfree
0 = register, 1 = unregister

Description

This adds the given notifier to the global list so that the callback is called for each registered PCM devices. This exists only for PCM OSS emulation, so far.

void snd_pcm_set_ops(struct snd_pcm * pcm, int direction, const struct snd_pcm_ops * ops)

set the PCM operators

Parameters

struct snd_pcm * pcm
the pcm instance
int direction
stream direction, SNDRV_PCM_STREAM_XXX
const struct snd_pcm_ops * ops
the operator table

Description

Sets the given PCM operators to the pcm instance.

void snd_pcm_set_sync(struct snd_pcm_substream * substream)

set the PCM sync id

Parameters

struct snd_pcm_substream * substream
the pcm substream

Description

Sets the PCM sync identifier for the card.

int snd_interval_refine(struct snd_interval * i, const struct snd_interval * v)

refine the interval value of configurator

Parameters

struct snd_interval * i
the interval value to refine
const struct snd_interval * v
the interval value to refer to

Description

Refines the interval value with the reference value. The interval is changed to the range satisfying both intervals. The interval status (min, max, integer, etc.) are evaluated.

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

int snd_interval_ratnum(struct snd_interval * i, unsigned int rats_count, const struct snd_ratnum * rats, unsigned int * nump, unsigned int * denp)

refine the interval value

Parameters

struct snd_interval * i
interval to refine
unsigned int rats_count
number of ratnum_t
const struct snd_ratnum * rats
ratnum_t array
unsigned int * nump
pointer to store the resultant numerator
unsigned int * denp
pointer to store the resultant denominator

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

int snd_interval_list(struct snd_interval * i, unsigned int count, const unsigned int * list, unsigned int mask)

refine the interval value from the list

Parameters

struct snd_interval * i
the interval value to refine
unsigned int count
the number of elements in the list
const unsigned int * list
the value list
unsigned int mask
the bit-mask to evaluate

Description

Refines the interval value from the list. When mask is non-zero, only the elements corresponding to bit 1 are evaluated.

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

int snd_interval_ranges(struct snd_interval * i, unsigned int count, const struct snd_interval * ranges, unsigned int mask)

refine the interval value from the list of ranges

Parameters

struct snd_interval * i
the interval value to refine
unsigned int count
the number of elements in the list of ranges
const struct snd_interval * ranges
the ranges list
unsigned int mask
the bit-mask to evaluate

Description

Refines the interval value from the list of ranges. When mask is non-zero, only the elements corresponding to bit 1 are evaluated.

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

int snd_pcm_hw_rule_add(struct snd_pcm_runtime * runtime, unsigned int cond, int var, snd_pcm_hw_rule_func_t func, void * private, int dep, ...)

add the hw-constraint rule

Parameters

struct snd_pcm_runtime * runtime
the pcm runtime instance
unsigned int cond
condition bits
int var
the variable to evaluate
snd_pcm_hw_rule_func_t func
the evaluation function
void * private
the private data pointer passed to function
int dep
the dependent variables
...
variable arguments

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_mask64(struct snd_pcm_runtime * runtime, snd_pcm_hw_param_t var, u_int64_t mask)

apply the given bitmap mask constraint

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
snd_pcm_hw_param_t var
hw_params variable to apply the mask
u_int64_t mask
the 64bit bitmap mask

Description

Apply the constraint of the given bitmap mask to a 64-bit mask parameter.

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_integer(struct snd_pcm_runtime * runtime, snd_pcm_hw_param_t var)

apply an integer constraint to an interval

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
snd_pcm_hw_param_t var
hw_params variable to apply the integer constraint

Description

Apply the constraint of integer to an interval parameter.

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

int snd_pcm_hw_constraint_minmax(struct snd_pcm_runtime * runtime, snd_pcm_hw_param_t var, unsigned int min, unsigned int max)

apply a min/max range constraint to an interval

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
snd_pcm_hw_param_t var
hw_params variable to apply the range
unsigned int min
the minimal value
unsigned int max
the maximal value

Description

Apply the min/max range constraint to an interval parameter.

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

int snd_pcm_hw_constraint_list(struct snd_pcm_runtime * runtime, unsigned int cond, snd_pcm_hw_param_t var, const struct snd_pcm_hw_constraint_list * l)

apply a list of constraints to a parameter

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
unsigned int cond
condition bits
snd_pcm_hw_param_t var
hw_params variable to apply the list constraint
const struct snd_pcm_hw_constraint_list * l
list

Description

Apply the list of constraints to an interval parameter.

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_ranges(struct snd_pcm_runtime * runtime, unsigned int cond, snd_pcm_hw_param_t var, const struct snd_pcm_hw_constraint_ranges * r)

apply list of range constraints to a parameter

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
unsigned int cond
condition bits
snd_pcm_hw_param_t var
hw_params variable to apply the list of range constraints
const struct snd_pcm_hw_constraint_ranges * r
ranges

Description

Apply the list of range constraints to an interval parameter.

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_ratnums(struct snd_pcm_runtime * runtime, unsigned int cond, snd_pcm_hw_param_t var, const struct snd_pcm_hw_constraint_ratnums * r)

apply ratnums constraint to a parameter

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
unsigned int cond
condition bits
snd_pcm_hw_param_t var
hw_params variable to apply the ratnums constraint
const struct snd_pcm_hw_constraint_ratnums * r
struct snd_ratnums constriants

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_ratdens(struct snd_pcm_runtime * runtime, unsigned int cond, snd_pcm_hw_param_t var, const struct snd_pcm_hw_constraint_ratdens * r)

apply ratdens constraint to a parameter

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
unsigned int cond
condition bits
snd_pcm_hw_param_t var
hw_params variable to apply the ratdens constraint
const struct snd_pcm_hw_constraint_ratdens * r
struct snd_ratdens constriants

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_msbits(struct snd_pcm_runtime * runtime, unsigned int cond, unsigned int width, unsigned int msbits)

add a hw constraint msbits rule

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
unsigned int cond
condition bits
unsigned int width
sample bits width
unsigned int msbits
msbits width

Description

This constraint will set the number of most significant bits (msbits) if a sample format with the specified width has been select. If width is set to 0 the msbits will be set for any sample format with a width larger than the specified msbits.

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_step(struct snd_pcm_runtime * runtime, unsigned int cond, snd_pcm_hw_param_t var, unsigned long step)

add a hw constraint step rule

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
unsigned int cond
condition bits
snd_pcm_hw_param_t var
hw_params variable to apply the step constraint
unsigned long step
step size

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_pow2(struct snd_pcm_runtime * runtime, unsigned int cond, snd_pcm_hw_param_t var)

add a hw constraint power-of-2 rule

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
unsigned int cond
condition bits
snd_pcm_hw_param_t var
hw_params variable to apply the power-of-2 constraint

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_rule_noresample(struct snd_pcm_runtime * runtime, unsigned int base_rate)

add a rule to allow disabling hw resampling

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
unsigned int base_rate
the rate at which the hardware does not resample

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_param_value(const struct snd_pcm_hw_params * params, snd_pcm_hw_param_t var, int * dir)

return params field var value

Parameters

const struct snd_pcm_hw_params * params
the hw_params instance
snd_pcm_hw_param_t var
parameter to retrieve
int * dir
pointer to the direction (-1,0,1) or NULL

Return

The value for field var if it’s fixed in configuration space defined by params. -EINVAL otherwise.

int snd_pcm_hw_param_first(struct snd_pcm_substream * pcm, struct snd_pcm_hw_params * params, snd_pcm_hw_param_t var, int * dir)

refine config space and return minimum value

Parameters

struct snd_pcm_substream * pcm
PCM instance
struct snd_pcm_hw_params * params
the hw_params instance
snd_pcm_hw_param_t var
parameter to retrieve
int * dir
pointer to the direction (-1,0,1) or NULL

Description

Inside configuration space defined by params remove from var all values > minimum. Reduce configuration space accordingly.

Return

The minimum, or a negative error code on failure.

int snd_pcm_hw_param_last(struct snd_pcm_substream * pcm, struct snd_pcm_hw_params * params, snd_pcm_hw_param_t var, int * dir)

refine config space and return maximum value

Parameters

struct snd_pcm_substream * pcm
PCM instance
struct snd_pcm_hw_params * params
the hw_params instance
snd_pcm_hw_param_t var
parameter to retrieve
int * dir
pointer to the direction (-1,0,1) or NULL

Description

Inside configuration space defined by params remove from var all values < maximum. Reduce configuration space accordingly.

Return

The maximum, or a negative error code on failure.

int snd_pcm_lib_ioctl(struct snd_pcm_substream * substream, unsigned int cmd, void * arg)

a generic PCM ioctl callback

Parameters

struct snd_pcm_substream * substream
the pcm substream instance
unsigned int cmd
ioctl command
void * arg
ioctl argument

Description

Processes the generic ioctl commands for PCM. Can be passed as the ioctl callback for PCM ops.

Return

Zero if successful, or a negative error code on failure.

void snd_pcm_period_elapsed(struct snd_pcm_substream * substream)

update the pcm status for the next period

Parameters

struct snd_pcm_substream * substream
the pcm substream instance

Description

This function is called from the interrupt handler when the PCM has processed the period size. It will update the current pointer, wake up sleepers, etc.

Even if more than one periods have elapsed since the last call, you have to call this only once.

int snd_pcm_add_chmap_ctls(struct snd_pcm * pcm, int stream, const struct snd_pcm_chmap_elem * chmap, int max_channels, unsigned long private_value, struct snd_pcm_chmap ** info_ret)

create channel-mapping control elements

Parameters

struct snd_pcm * pcm
the assigned PCM instance
int stream
stream direction
const struct snd_pcm_chmap_elem * chmap
channel map elements (for query)
int max_channels
the max number of channels for the stream
unsigned long private_value
the value passed to each kcontrol’s private_value field
struct snd_pcm_chmap ** info_ret
store struct snd_pcm_chmap instance if non-NULL

Description

Create channel-mapping control elements assigned to the given PCM stream(s).

Return

Zero if successful, or a negative error value.

void snd_pcm_stream_lock(struct snd_pcm_substream * substream)

Lock the PCM stream

Parameters

struct snd_pcm_substream * substream
PCM substream

Description

This locks the PCM stream’s spinlock or mutex depending on the nonatomic flag of the given substream. This also takes the global link rw lock (or rw sem), too, for avoiding the race with linked streams.

void snd_pcm_stream_unlock(struct snd_pcm_substream * substream)

Unlock the PCM stream

Parameters

struct snd_pcm_substream * substream
PCM substream

Description

This unlocks the PCM stream that has been locked via snd_pcm_stream_lock().

void snd_pcm_stream_lock_irq(struct snd_pcm_substream * substream)

Lock the PCM stream

Parameters

struct snd_pcm_substream * substream
PCM substream

Description

This locks the PCM stream like snd_pcm_stream_lock() and disables the local IRQ (only when nonatomic is false). In nonatomic case, this is identical as snd_pcm_stream_lock().

void snd_pcm_stream_unlock_irq(struct snd_pcm_substream * substream)

Unlock the PCM stream

Parameters

struct snd_pcm_substream * substream
PCM substream

Description

This is a counter-part of snd_pcm_stream_lock_irq().

void snd_pcm_stream_unlock_irqrestore(struct snd_pcm_substream * substream, unsigned long flags)

Unlock the PCM stream

Parameters

struct snd_pcm_substream * substream
PCM substream
unsigned long flags
irq flags

Description

This is a counter-part of snd_pcm_stream_lock_irqsave().

int snd_pcm_stop(struct snd_pcm_substream * substream, snd_pcm_state_t state)

try to stop all running streams in the substream group

Parameters

struct snd_pcm_substream * substream
the PCM substream instance
snd_pcm_state_t state
PCM state after stopping the stream

Description

The state of each stream is then changed to the given state unconditionally.

Return

Zero if successful, or a negative error code.

int snd_pcm_stop_xrun(struct snd_pcm_substream * substream)

stop the running streams as XRUN

Parameters

struct snd_pcm_substream * substream
the PCM substream instance

Description

This stops the given running substream (and all linked substreams) as XRUN. Unlike snd_pcm_stop(), this function takes the substream lock by itself.

Return

Zero if successful, or a negative error code.

int snd_pcm_suspend(struct snd_pcm_substream * substream)

trigger SUSPEND to all linked streams

Parameters

struct snd_pcm_substream * substream
the PCM substream

Description

After this call, all streams are changed to SUSPENDED state.

Return

Zero if successful (or substream is NULL), or a negative error code.

int snd_pcm_suspend_all(struct snd_pcm * pcm)

trigger SUSPEND to all substreams in the given pcm

Parameters

struct snd_pcm * pcm
the PCM instance

Description

After this call, all streams are changed to SUSPENDED state.

Return

Zero if successful (or pcm is NULL), or a negative error code.

int snd_pcm_lib_default_mmap(struct snd_pcm_substream * substream, struct vm_area_struct * area)

Default PCM data mmap function

Parameters

struct snd_pcm_substream * substream
PCM substream
struct vm_area_struct * area
VMA

Description

This is the default mmap handler for PCM data. When mmap pcm_ops is NULL, this function is invoked implicitly.

int snd_pcm_lib_mmap_iomem(struct snd_pcm_substream * substream, struct vm_area_struct * area)

Default PCM data mmap function for I/O mem

Parameters

struct snd_pcm_substream * substream
PCM substream
struct vm_area_struct * area
VMA

Description

When your hardware uses the iomapped pages as the hardware buffer and wants to mmap it, pass this function as mmap pcm_ops. Note that this is supposed to work only on limited architectures.

int snd_pcm_stream_linked(struct snd_pcm_substream * substream)

Check whether the substream is linked with others

Parameters

struct snd_pcm_substream * substream
substream to check

Description

Returns true if the given substream is being linked with others.

snd_pcm_stream_lock_irqsave(substream, flags)

Lock the PCM stream

Parameters

substream
PCM substream
flags
irq flags

Description

This locks the PCM stream like snd_pcm_stream_lock() but with the local IRQ (only when nonatomic is false). In nonatomic case, this is identical as snd_pcm_stream_lock().

snd_pcm_group_for_each_entry(s, substream)

iterate over the linked substreams

Parameters

s
the iterator
substream
the substream

Description

Iterate over the all linked substreams to the given substream. When substream isn’t linked with any others, this gives returns substream itself once.

int snd_pcm_running(struct snd_pcm_substream * substream)

Check whether the substream is in a running state

Parameters

struct snd_pcm_substream * substream
substream to check

Description

Returns true if the given substream is in the state RUNNING, or in the state DRAINING for playback.

ssize_t bytes_to_samples(struct snd_pcm_runtime * runtime, ssize_t size)

Unit conversion of the size from bytes to samples

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
ssize_t size
size in bytes
snd_pcm_sframes_t bytes_to_frames(struct snd_pcm_runtime * runtime, ssize_t size)

Unit conversion of the size from bytes to frames

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
ssize_t size
size in bytes
ssize_t samples_to_bytes(struct snd_pcm_runtime * runtime, ssize_t size)

Unit conversion of the size from samples to bytes

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
ssize_t size
size in samples
ssize_t frames_to_bytes(struct snd_pcm_runtime * runtime, snd_pcm_sframes_t size)

Unit conversion of the size from frames to bytes

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
snd_pcm_sframes_t size
size in frames
int frame_aligned(struct snd_pcm_runtime * runtime, ssize_t bytes)

Check whether the byte size is aligned to frames

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
ssize_t bytes
size in bytes
size_t snd_pcm_lib_buffer_bytes(struct snd_pcm_substream * substream)

Get the buffer size of the current PCM in bytes

Parameters

struct snd_pcm_substream * substream
PCM substream
size_t snd_pcm_lib_period_bytes(struct snd_pcm_substream * substream)

Get the period size of the current PCM in bytes

Parameters

struct snd_pcm_substream * substream
PCM substream
snd_pcm_uframes_t snd_pcm_playback_avail(struct snd_pcm_runtime * runtime)

Get the available (writable) space for playback

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance

Description

Result is between 0 ... (boundary - 1)

snd_pcm_uframes_t snd_pcm_capture_avail(struct snd_pcm_runtime * runtime)

Get the available (readable) space for capture

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance

Description

Result is between 0 ... (boundary - 1)

snd_pcm_sframes_t snd_pcm_playback_hw_avail(struct snd_pcm_runtime * runtime)

Get the queued space for playback

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
snd_pcm_sframes_t snd_pcm_capture_hw_avail(struct snd_pcm_runtime * runtime)

Get the free space for capture

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
int snd_pcm_playback_ready(struct snd_pcm_substream * substream)

check whether the playback buffer is available

Parameters

struct snd_pcm_substream * substream
the pcm substream instance

Description

Checks whether enough free space is available on the playback buffer.

Return

Non-zero if available, or zero if not.

int snd_pcm_capture_ready(struct snd_pcm_substream * substream)

check whether the capture buffer is available

Parameters

struct snd_pcm_substream * substream
the pcm substream instance

Description

Checks whether enough capture data is available on the capture buffer.

Return

Non-zero if available, or zero if not.

int snd_pcm_playback_data(struct snd_pcm_substream * substream)

check whether any data exists on the playback buffer

Parameters

struct snd_pcm_substream * substream
the pcm substream instance

Description

Checks whether any data exists on the playback buffer.

Return

Non-zero if any data exists, or zero if not. If stop_threshold is bigger or equal to boundary, then this function returns always non-zero.

int snd_pcm_playback_empty(struct snd_pcm_substream * substream)

check whether the playback buffer is empty

Parameters

struct snd_pcm_substream * substream
the pcm substream instance

Description

Checks whether the playback buffer is empty.

Return

Non-zero if empty, or zero if not.

int snd_pcm_capture_empty(struct snd_pcm_substream * substream)

check whether the capture buffer is empty

Parameters

struct snd_pcm_substream * substream
the pcm substream instance

Description

Checks whether the capture buffer is empty.

Return

Non-zero if empty, or zero if not.

void snd_pcm_trigger_done(struct snd_pcm_substream * substream, struct snd_pcm_substream * master)

Mark the master substream

Parameters

struct snd_pcm_substream * substream
the pcm substream instance
struct snd_pcm_substream * master
the linked master substream

Description

When multiple substreams of the same card are linked and the hardware supports the single-shot operation, the driver calls this in the loop in snd_pcm_group_for_each_entry() for marking the substream as “done”. Then most of trigger operations are performed only to the given master substream.

The trigger_master mark is cleared at timestamp updates at the end of trigger operations.

unsigned int params_channels(const struct snd_pcm_hw_params * p)

Get the number of channels from the hw params

Parameters

const struct snd_pcm_hw_params * p
hw params
unsigned int params_rate(const struct snd_pcm_hw_params * p)

Get the sample rate from the hw params

Parameters

const struct snd_pcm_hw_params * p
hw params
unsigned int params_period_size(const struct snd_pcm_hw_params * p)

Get the period size (in frames) from the hw params

Parameters

const struct snd_pcm_hw_params * p
hw params
unsigned int params_periods(const struct snd_pcm_hw_params * p)

Get the number of periods from the hw params

Parameters

const struct snd_pcm_hw_params * p
hw params
unsigned int params_buffer_size(const struct snd_pcm_hw_params * p)

Get the buffer size (in frames) from the hw params

Parameters

const struct snd_pcm_hw_params * p
hw params
unsigned int params_buffer_bytes(const struct snd_pcm_hw_params * p)

Get the buffer size (in bytes) from the hw params

Parameters

const struct snd_pcm_hw_params * p
hw params
int snd_pcm_hw_constraint_single(struct snd_pcm_runtime * runtime, snd_pcm_hw_param_t var, unsigned int val)

Constrain parameter to a single value

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
snd_pcm_hw_param_t var
The hw_params variable to constrain
unsigned int val
The value to constrain to

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

int snd_pcm_format_cpu_endian(snd_pcm_format_t format)

Check the PCM format is CPU-endian

Parameters

snd_pcm_format_t format
the format to check

Return

1 if the given PCM format is CPU-endian, 0 if opposite, or a negative error code if endian not specified.

void snd_pcm_set_runtime_buffer(struct snd_pcm_substream * substream, struct snd_dma_buffer * bufp)

Set the PCM runtime buffer

Parameters

struct snd_pcm_substream * substream
PCM substream to set
struct snd_dma_buffer * bufp
the buffer information, NULL to clear

Description

Copy the buffer information to runtime->dma_buffer when bufp is non-NULL. Otherwise it clears the current buffer information.

void snd_pcm_gettime(struct snd_pcm_runtime * runtime, struct timespec * tv)

Fill the timespec depending on the timestamp mode

Parameters

struct snd_pcm_runtime * runtime
PCM runtime instance
struct timespec * tv
timespec to fill
int snd_pcm_lib_alloc_vmalloc_buffer(struct snd_pcm_substream * substream, size_t size)

allocate virtual DMA buffer

Parameters

struct snd_pcm_substream * substream
the substream to allocate the buffer to
size_t size
the requested buffer size, in bytes

Description

Allocates the PCM substream buffer using vmalloc(), i.e., the memory is contiguous in kernel virtual space, but not in physical memory. Use this if the buffer is accessed by kernel code but not by device DMA.

Return

1 if the buffer was changed, 0 if not changed, or a negative error code.

int snd_pcm_lib_alloc_vmalloc_32_buffer(struct snd_pcm_substream * substream, size_t size)

allocate 32-bit-addressable buffer

Parameters

struct snd_pcm_substream * substream
the substream to allocate the buffer to
size_t size
the requested buffer size, in bytes

Description

This function works like snd_pcm_lib_alloc_vmalloc_buffer(), but uses vmalloc_32(), i.e., the pages are allocated from 32-bit-addressable memory.

Return

1 if the buffer was changed, 0 if not changed, or a negative error code.

dma_addr_t snd_pcm_sgbuf_get_addr(struct snd_pcm_substream * substream, unsigned int ofs)

Get the DMA address at the corresponding offset

Parameters

struct snd_pcm_substream * substream
PCM substream
unsigned int ofs
byte offset
void * snd_pcm_sgbuf_get_ptr(struct snd_pcm_substream * substream, unsigned int ofs)

Get the virtual address at the corresponding offset

Parameters

struct snd_pcm_substream * substream
PCM substream
unsigned int ofs
byte offset
unsigned int snd_pcm_sgbuf_get_chunk_size(struct snd_pcm_substream * substream, unsigned int ofs, unsigned int size)

Compute the max size that fits within the contig. page from the given size

Parameters

struct snd_pcm_substream * substream
PCM substream
unsigned int ofs
byte offset
unsigned int size
byte size to examine
void snd_pcm_mmap_data_open(struct vm_area_struct * area)

increase the mmap counter

Parameters

struct vm_area_struct * area
VMA

Description

PCM mmap callback should handle this counter properly

void snd_pcm_mmap_data_close(struct vm_area_struct * area)

decrease the mmap counter

Parameters

struct vm_area_struct * area
VMA

Description

PCM mmap callback should handle this counter properly

void snd_pcm_limit_isa_dma_size(int dma, size_t * max)

Get the max size fitting with ISA DMA transfer

Parameters

int dma
DMA number
size_t * max
pointer to store the max size
const char * snd_pcm_stream_str(struct snd_pcm_substream * substream)

Get a string naming the direction of a stream

Parameters

struct snd_pcm_substream * substream
the pcm substream instance

Return

A string naming the direction of the stream.

struct snd_pcm_substream * snd_pcm_chmap_substream(struct snd_pcm_chmap * info, unsigned int idx)

get the PCM substream assigned to the given chmap info

Parameters

struct snd_pcm_chmap * info
chmap information
unsigned int idx
the substream number index
u64 pcm_format_to_bits(snd_pcm_format_t pcm_format)

Strong-typed conversion of pcm_format to bitwise

Parameters

snd_pcm_format_t pcm_format
PCM format

PCM Format Helpers

int snd_pcm_format_signed(snd_pcm_format_t format)

Check the PCM format is signed linear

Parameters

snd_pcm_format_t format
the format to check

Return

1 if the given PCM format is signed linear, 0 if unsigned linear, and a negative error code for non-linear formats.

int snd_pcm_format_unsigned(snd_pcm_format_t format)

Check the PCM format is unsigned linear

Parameters

snd_pcm_format_t format
the format to check

Return

1 if the given PCM format is unsigned linear, 0 if signed linear, and a negative error code for non-linear formats.

int snd_pcm_format_linear(snd_pcm_format_t format)

Check the PCM format is linear

Parameters

snd_pcm_format_t format
the format to check

Return

1 if the given PCM format is linear, 0 if not.

int snd_pcm_format_little_endian(snd_pcm_format_t format)

Check the PCM format is little-endian

Parameters

snd_pcm_format_t format
the format to check

Return

1 if the given PCM format is little-endian, 0 if big-endian, or a negative error code if endian not specified.

int snd_pcm_format_big_endian(snd_pcm_format_t format)

Check the PCM format is big-endian

Parameters

snd_pcm_format_t format
the format to check

Return

1 if the given PCM format is big-endian, 0 if little-endian, or a negative error code if endian not specified.

int snd_pcm_format_width(snd_pcm_format_t format)

return the bit-width of the format

Parameters

snd_pcm_format_t format
the format to check

Return

The bit-width of the format, or a negative error code if unknown format.

int snd_pcm_format_physical_width(snd_pcm_format_t format)

return the physical bit-width of the format

Parameters

snd_pcm_format_t format
the format to check

Return

The physical bit-width of the format, or a negative error code if unknown format.

ssize_t snd_pcm_format_size(snd_pcm_format_t format, size_t samples)

return the byte size of samples on the given format

Parameters

snd_pcm_format_t format
the format to check
size_t samples
sampling rate

Return

The byte size of the given samples for the format, or a negative error code if unknown format.

const unsigned char * snd_pcm_format_silence_64(snd_pcm_format_t format)

return the silent data in 8 bytes array

Parameters

snd_pcm_format_t format
the format to check

Return

The format pattern to fill or NULL if error.

int snd_pcm_format_set_silence(snd_pcm_format_t format, void * data, unsigned int samples)

set the silence data on the buffer

Parameters

snd_pcm_format_t format
the PCM format
void * data
the buffer pointer
unsigned int samples
the number of samples to set silence

Description

Sets the silence data on the buffer for the given samples.

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_limit_hw_rates(struct snd_pcm_runtime * runtime)

determine rate_min/rate_max fields

Parameters

struct snd_pcm_runtime * runtime
the runtime instance

Description

Determines the rate_min and rate_max fields from the rates bits of the given runtime->hw.

Return

Zero if successful.

unsigned int snd_pcm_rate_to_rate_bit(unsigned int rate)

converts sample rate to SNDRV_PCM_RATE_xxx bit

Parameters

unsigned int rate
the sample rate to convert

Return

The SNDRV_PCM_RATE_xxx flag that corresponds to the given rate, or SNDRV_PCM_RATE_KNOT for an unknown rate.

unsigned int snd_pcm_rate_bit_to_rate(unsigned int rate_bit)

converts SNDRV_PCM_RATE_xxx bit to sample rate

Parameters

unsigned int rate_bit
the rate bit to convert

Return

The sample rate that corresponds to the given SNDRV_PCM_RATE_xxx flag or 0 for an unknown rate bit.

unsigned int snd_pcm_rate_mask_intersect(unsigned int rates_a, unsigned int rates_b)

computes the intersection between two rate masks

Parameters

unsigned int rates_a
The first rate mask
unsigned int rates_b
The second rate mask

Description

This function computes the rates that are supported by both rate masks passed to the function. It will take care of the special handling of SNDRV_PCM_RATE_CONTINUOUS and SNDRV_PCM_RATE_KNOT.

Return

A rate mask containing the rates that are supported by both rates_a and rates_b.

unsigned int snd_pcm_rate_range_to_bits(unsigned int rate_min, unsigned int rate_max)

converts rate range to SNDRV_PCM_RATE_xxx bit

Parameters

unsigned int rate_min
the minimum sample rate
unsigned int rate_max
the maximum sample rate

Description

This function has an implicit assumption: the rates in the given range have only the pre-defined rates like 44100 or 16000.

Return

The SNDRV_PCM_RATE_xxx flag that corresponds to the given rate range, or SNDRV_PCM_RATE_KNOT for an unknown range.

PCM Memory Management

int snd_pcm_lib_preallocate_free_for_all(struct snd_pcm * pcm)

release all pre-allocated buffers on the pcm

Parameters

struct snd_pcm * pcm
the pcm instance

Description

Releases all the pre-allocated buffers on the given pcm.

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_lib_preallocate_pages(struct snd_pcm_substream * substream, int type, struct device * data, size_t size, size_t max)

pre-allocation for the given DMA type

Parameters

struct snd_pcm_substream * substream
the pcm substream instance
int type
DMA type (SNDRV_DMA_TYPE_*)
struct device * data
DMA type dependent data
size_t size
the requested pre-allocation size in bytes
size_t max
the max. allowed pre-allocation size

Description

Do pre-allocation for the given DMA buffer type.

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_lib_preallocate_pages_for_all(struct snd_pcm * pcm, int type, void * data, size_t size, size_t max)

pre-allocation for continuous memory type (all substreams)

Parameters

struct snd_pcm * pcm
the pcm instance
int type
DMA type (SNDRV_DMA_TYPE_*)
void * data
DMA type dependent data
size_t size
the requested pre-allocation size in bytes
size_t max
the max. allowed pre-allocation size

Description

Do pre-allocation to all substreams of the given pcm for the specified DMA type.

Return

Zero if successful, or a negative error code on failure.

struct page * snd_pcm_sgbuf_ops_page(struct snd_pcm_substream * substream, unsigned long offset)

get the page struct at the given offset

Parameters

struct snd_pcm_substream * substream
the pcm substream instance
unsigned long offset
the buffer offset

Description

Used as the page callback of PCM ops.

Return

The page struct at the given buffer offset. NULL on failure.

int snd_pcm_lib_malloc_pages(struct snd_pcm_substream * substream, size_t size)

allocate the DMA buffer

Parameters

struct snd_pcm_substream * substream
the substream to allocate the DMA buffer to
size_t size
the requested buffer size in bytes

Description

Allocates the DMA buffer on the BUS type given earlier to snd_pcm_lib_preallocate_xxx_pages().

Return

1 if the buffer is changed, 0 if not changed, or a negative code on failure.

int snd_pcm_lib_free_pages(struct snd_pcm_substream * substream)

release the allocated DMA buffer.

Parameters

struct snd_pcm_substream * substream
the substream to release the DMA buffer

Description

Releases the DMA buffer allocated via snd_pcm_lib_malloc_pages().

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_lib_free_vmalloc_buffer(struct snd_pcm_substream * substream)

free vmalloc buffer

Parameters

struct snd_pcm_substream * substream
the substream with a buffer allocated by snd_pcm_lib_alloc_vmalloc_buffer()

Return

Zero if successful, or a negative error code on failure.

struct page * snd_pcm_lib_get_vmalloc_page(struct snd_pcm_substream * substream, unsigned long offset)

map vmalloc buffer offset to page struct

Parameters

struct snd_pcm_substream * substream
the substream with a buffer allocated by snd_pcm_lib_alloc_vmalloc_buffer()
unsigned long offset
offset in the buffer

Description

This function is to be used as the page callback in the PCM ops.

Return

The page struct, or NULL on failure.

PCM DMA Engine API

int snd_hwparams_to_dma_slave_config(const struct snd_pcm_substream * substream, const struct snd_pcm_hw_params * params, struct dma_slave_config * slave_config)

Convert hw_params to dma_slave_config

Parameters

const struct snd_pcm_substream * substream
PCM substream
const struct snd_pcm_hw_params * params
hw_params
struct dma_slave_config * slave_config
DMA slave config

Description

This function can be used to initialize a dma_slave_config from a substream and hw_params in a dmaengine based PCM driver implementation.

void snd_dmaengine_pcm_set_config_from_dai_data(const struct snd_pcm_substream * substream, const struct snd_dmaengine_dai_dma_data * dma_data, struct dma_slave_config * slave_config)

Initializes a dma slave config using DAI DMA data.

Parameters

const struct snd_pcm_substream * substream
PCM substream
const struct snd_dmaengine_dai_dma_data * dma_data
DAI DMA data
struct dma_slave_config * slave_config
DMA slave configuration

Description

Initializes the {dst,src}_addr, {dst,src}_maxburst, {dst,src}_addr_width and slave_id fields of the DMA slave config from the same fields of the DAI DMA data struct. The src and dst fields will be initialized depending on the direction of the substream. If the substream is a playback stream the dst fields will be initialized, if it is a capture stream the src fields will be initialized. The {dst,src}_addr_width field will only be initialized if the SND_DMAENGINE_PCM_DAI_FLAG_PACK flag is set or if the addr_width field of the DAI DMA data struct is not equal to DMA_SLAVE_BUSWIDTH_UNDEFINED. If both conditions are met the latter takes priority.

int snd_dmaengine_pcm_trigger(struct snd_pcm_substream * substream, int cmd)

dmaengine based PCM trigger implementation

Parameters

struct snd_pcm_substream * substream
PCM substream
int cmd
Trigger command

Description

Returns 0 on success, a negative error code otherwise.

This function can be used as the PCM trigger callback for dmaengine based PCM driver implementations.

snd_pcm_uframes_t snd_dmaengine_pcm_pointer_no_residue(struct snd_pcm_substream * substream)

dmaengine based PCM pointer implementation

Parameters

struct snd_pcm_substream * substream
PCM substream

Description

This function is deprecated and should not be used by new drivers, as its results may be unreliable.

snd_pcm_uframes_t snd_dmaengine_pcm_pointer(struct snd_pcm_substream * substream)

dmaengine based PCM pointer implementation

Parameters

struct snd_pcm_substream * substream
PCM substream

Description

This function can be used as the PCM pointer callback for dmaengine based PCM driver implementations.

struct dma_chan * snd_dmaengine_pcm_request_channel(dma_filter_fn filter_fn, void * filter_data)

Request channel for the dmaengine PCM

Parameters

dma_filter_fn filter_fn
Filter function used to request the DMA channel
void * filter_data
Data passed to the DMA filter function

Description

Returns NULL or the requested DMA channel.

This function request a DMA channel for usage with dmaengine PCM.

int snd_dmaengine_pcm_open(struct snd_pcm_substream * substream, struct dma_chan * chan)

Open a dmaengine based PCM substream

Parameters

struct snd_pcm_substream * substream
PCM substream
struct dma_chan * chan
DMA channel to use for data transfers

Description

Returns 0 on success, a negative error code otherwise.

The function should usually be called from the pcm open callback. Note that this function will use private_data field of the substream’s runtime. So it is not available to your pcm driver implementation.

int snd_dmaengine_pcm_open_request_chan(struct snd_pcm_substream * substream, dma_filter_fn filter_fn, void * filter_data)

Open a dmaengine based PCM substream and request channel

Parameters

struct snd_pcm_substream * substream
PCM substream
dma_filter_fn filter_fn
Filter function used to request the DMA channel
void * filter_data
Data passed to the DMA filter function

Description

Returns 0 on success, a negative error code otherwise.

This function will request a DMA channel using the passed filter function and data. The function should usually be called from the pcm open callback. Note that this function will use private_data field of the substream’s runtime. So it is not available to your pcm driver implementation.

int snd_dmaengine_pcm_close(struct snd_pcm_substream * substream)

Close a dmaengine based PCM substream

Parameters

struct snd_pcm_substream * substream
PCM substream
int snd_dmaengine_pcm_close_release_chan(struct snd_pcm_substream * substream)

Close a dmaengine based PCM substream and release channel

Parameters

struct snd_pcm_substream * substream
PCM substream

Description

Releases the DMA channel associated with the PCM substream.

enum dma_transfer_direction snd_pcm_substream_to_dma_direction(const struct snd_pcm_substream * substream)

Get dma_transfer_direction for a PCM substream

Parameters

const struct snd_pcm_substream * substream
PCM substream
struct snd_dmaengine_dai_dma_data

DAI DMA configuration data

Definition

struct snd_dmaengine_dai_dma_data {
  dma_addr_t addr;
  enum dma_slave_buswidth addr_width;
  u32 maxburst;
  unsigned int slave_id;
  void * filter_data;
  const char * chan_name;
  unsigned int fifo_size;
  unsigned int flags;
};

Members

dma_addr_t addr
Address of the DAI data source or destination register.
enum dma_slave_buswidth addr_width
Width of the DAI data source or destination register.
u32 maxburst
Maximum number of words(note: words, as in units of the src_addr_width member, not bytes) that can be send to or received from the DAI in one burst.
unsigned int slave_id
Slave requester id for the DMA channel.
void * filter_data
Custom DMA channel filter data, this will usually be used when requesting the DMA channel.
const char * chan_name
Custom channel name to use when requesting DMA channel.
unsigned int fifo_size
FIFO size of the DAI controller in bytes
unsigned int flags
PCM_DAI flags, only SND_DMAENGINE_PCM_DAI_FLAG_PACK for now
struct snd_dmaengine_pcm_config

Configuration data for dmaengine based PCM

Definition

struct snd_dmaengine_pcm_config {
  int (* prepare_slave_config) (struct snd_pcm_substream *substream,struct snd_pcm_hw_params *params,struct dma_slave_config *slave_config);
  struct dma_chan *(* compat_request_channel) (struct snd_soc_pcm_runtime *rtd,struct snd_pcm_substream *substream);
  dma_filter_fn compat_filter_fn;
  struct device * dma_dev;
  const char * chan_names[SNDRV_PCM_STREAM_LAST + 1];
  const struct snd_pcm_hardware * pcm_hardware;
  unsigned int prealloc_buffer_size;
};

Members

int (*)(struct snd_pcm_substream *substream,struct snd_pcm_hw_params *params,struct dma_slave_config *slave_config) prepare_slave_config
Callback used to fill in the DMA slave_config for a PCM substream. Will be called from the PCM drivers hwparams callback.
struct dma_chan *(*)(struct snd_soc_pcm_runtime *rtd,struct snd_pcm_substream *substream) compat_request_channel
Callback to request a DMA channel for platforms which do not use devicetree.
dma_filter_fn compat_filter_fn
Will be used as the filter function when requesting a channel for platforms which do not use devicetree. The filter parameter will be the DAI’s DMA data.
struct device * dma_dev
If set, request DMA channel on this device rather than the DAI device.
const char * chan_names[SNDRV_PCM_STREAM_LAST + 1]
If set, these custom DMA channel names will be requested at registration time.
const struct snd_pcm_hardware * pcm_hardware
snd_pcm_hardware struct to be used for the PCM.
unsigned int prealloc_buffer_size
Size of the preallocated audio buffer.

Note

If both compat_request_channel and compat_filter_fn are set compat_request_channel will be used to request the channel and compat_filter_fn will be ignored. Otherwise the channel will be requested using dma_request_channel with compat_filter_fn as the filter function.

Control/Mixer API

General Control Interface

void snd_ctl_notify(struct snd_card * card, unsigned int mask, struct snd_ctl_elem_id * id)

Send notification to user-space for a control change

Parameters

struct snd_card * card
the card to send notification
unsigned int mask
the event mask, SNDRV_CTL_EVENT_*
struct snd_ctl_elem_id * id
the ctl element id to send notification

Description

This function adds an event record with the given id and mask, appends to the list and wakes up the user-space for notification. This can be called in the atomic context.

struct snd_kcontrol * snd_ctl_new1(const struct snd_kcontrol_new * ncontrol, void * private_data)

create a control instance from the template

Parameters

const struct snd_kcontrol_new * ncontrol
the initialization record
void * private_data
the private data to set

Description

Allocates a new struct snd_kcontrol instance and initialize from the given template. When the access field of ncontrol is 0, it’s assumed as READWRITE access. When the count field is 0, it’s assumes as one.

Return

The pointer of the newly generated instance, or NULL on failure.

void snd_ctl_free_one(struct snd_kcontrol * kcontrol)

release the control instance

Parameters

struct snd_kcontrol * kcontrol
the control instance

Description

Releases the control instance created via snd_ctl_new() or snd_ctl_new1(). Don’t call this after the control was added to the card.

int snd_ctl_add(struct snd_card * card, struct snd_kcontrol * kcontrol)

add the control instance to the card

Parameters

struct snd_card * card
the card instance
struct snd_kcontrol * kcontrol
the control instance to add

Description

Adds the control instance created via snd_ctl_new() or snd_ctl_new1() to the given card. Assigns also an unique numid used for fast search.

It frees automatically the control which cannot be added.

Return

Zero if successful, or a negative error code on failure.

int snd_ctl_replace(struct snd_card * card, struct snd_kcontrol * kcontrol, bool add_on_replace)

replace the control instance of the card

Parameters

struct snd_card * card
the card instance
struct snd_kcontrol * kcontrol
the control instance to replace
bool add_on_replace
add the control if not already added

Description

Replaces the given control. If the given control does not exist and the add_on_replace flag is set, the control is added. If the control exists, it is destroyed first.

It frees automatically the control which cannot be added or replaced.

Return

Zero if successful, or a negative error code on failure.

int snd_ctl_remove(struct snd_card * card, struct snd_kcontrol * kcontrol)

remove the control from the card and release it

Parameters

struct snd_card * card
the card instance
struct snd_kcontrol * kcontrol
the control instance to remove

Description

Removes the control from the card and then releases the instance. You don’t need to call snd_ctl_free_one(). You must be in the write lock - down_write(card->controls_rwsem).

Return

0 if successful, or a negative error code on failure.

int snd_ctl_remove_id(struct snd_card * card, struct snd_ctl_elem_id * id)

remove the control of the given id and release it

Parameters

struct snd_card * card
the card instance
struct snd_ctl_elem_id * id
the control id to remove

Description

Finds the control instance with the given id, removes it from the card list and releases it.

Return

0 if successful, or a negative error code on failure.

int snd_ctl_activate_id(struct snd_card * card, struct snd_ctl_elem_id * id, int active)

activate/inactivate the control of the given id

Parameters

struct snd_card * card
the card instance
struct snd_ctl_elem_id * id
the control id to activate/inactivate
int active
non-zero to activate

Description

Finds the control instance with the given id, and activate or inactivate the control together with notification, if changed. The given ID data is filled with full information.

Return

0 if unchanged, 1 if changed, or a negative error code on failure.

int snd_ctl_rename_id(struct snd_card * card, struct snd_ctl_elem_id * src_id, struct snd_ctl_elem_id * dst_id)

replace the id of a control on the card

Parameters

struct snd_card * card
the card instance
struct snd_ctl_elem_id * src_id
the old id
struct snd_ctl_elem_id * dst_id
the new id

Description

Finds the control with the old id from the card, and replaces the id with the new one.

Return

Zero if successful, or a negative error code on failure.

struct snd_kcontrol * snd_ctl_find_numid(struct snd_card * card, unsigned int numid)

find the control instance with the given number-id

Parameters

struct snd_card * card
the card instance
unsigned int numid
the number-id to search

Description

Finds the control instance with the given number-id from the card.

The caller must down card->controls_rwsem before calling this function (if the race condition can happen).

Return

The pointer of the instance if found, or NULL if not.

struct snd_kcontrol * snd_ctl_find_id(struct snd_card * card, struct snd_ctl_elem_id * id)

find the control instance with the given id

Parameters

struct snd_card * card
the card instance
struct snd_ctl_elem_id * id
the id to search

Description

Finds the control instance with the given id from the card.

The caller must down card->controls_rwsem before calling this function (if the race condition can happen).

Return

The pointer of the instance if found, or NULL if not.

int snd_ctl_register_ioctl(snd_kctl_ioctl_func_t fcn)

register the device-specific control-ioctls

Parameters

snd_kctl_ioctl_func_t fcn
ioctl callback function

Description

called from each device manager like pcm.c, hwdep.c, etc.

int snd_ctl_register_ioctl_compat(snd_kctl_ioctl_func_t fcn)

register the device-specific 32bit compat control-ioctls

Parameters

snd_kctl_ioctl_func_t fcn
ioctl callback function
int snd_ctl_unregister_ioctl(snd_kctl_ioctl_func_t fcn)

de-register the device-specific control-ioctls

Parameters

snd_kctl_ioctl_func_t fcn
ioctl callback function to unregister
int snd_ctl_unregister_ioctl_compat(snd_kctl_ioctl_func_t fcn)

de-register the device-specific compat 32bit control-ioctls

Parameters

snd_kctl_ioctl_func_t fcn
ioctl callback function to unregister
int snd_ctl_boolean_mono_info(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_info * uinfo)

Helper function for a standard boolean info callback with a mono channel

Parameters

struct snd_kcontrol * kcontrol
the kcontrol instance
struct snd_ctl_elem_info * uinfo
info to store

Description

This is a function that can be used as info callback for a standard boolean control with a single mono channel.

int snd_ctl_boolean_stereo_info(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_info * uinfo)

Helper function for a standard boolean info callback with stereo two channels

Parameters

struct snd_kcontrol * kcontrol
the kcontrol instance
struct snd_ctl_elem_info * uinfo
info to store

Description

This is a function that can be used as info callback for a standard boolean control with stereo two channels.

int snd_ctl_enum_info(struct snd_ctl_elem_info * info, unsigned int channels, unsigned int items, const char *const names[])

fills the info structure for an enumerated control

Parameters

struct snd_ctl_elem_info * info
the structure to be filled
unsigned int channels
the number of the control’s channels; often one
unsigned int items
the number of control values; also the size of names
const char *const names[]
undescribed

Description

Sets all required fields in info to their appropriate values. If the control’s accessibility is not the default (readable and writable), the caller has to fill info->access.

Return

Zero.

AC97 Codec API

void snd_ac97_write(struct snd_ac97 * ac97, unsigned short reg, unsigned short value)

write a value on the given register

Parameters

struct snd_ac97 * ac97
the ac97 instance
unsigned short reg
the register to change
unsigned short value
the value to set

Description

Writes a value on the given register. This will invoke the write callback directly after the register check. This function doesn’t change the register cache unlike #:c:func:snd_ca97_write_cache(), so use this only when you don’t want to reflect the change to the suspend/resume state.

unsigned short snd_ac97_read(struct snd_ac97 * ac97, unsigned short reg)

read a value from the given register

Parameters

struct snd_ac97 * ac97
the ac97 instance
unsigned short reg
the register to read

Description

Reads a value from the given register. This will invoke the read callback directly after the register check.

Return

The read value.

void snd_ac97_write_cache(struct snd_ac97 * ac97, unsigned short reg, unsigned short value)

write a value on the given register and update the cache

Parameters

struct snd_ac97 * ac97
the ac97 instance
unsigned short reg
the register to change
unsigned short value
the value to set

Description

Writes a value on the given register and updates the register cache. The cached values are used for the cached-read and the suspend/resume.

int snd_ac97_update(struct snd_ac97 * ac97, unsigned short reg, unsigned short value)

update the value on the given register

Parameters

struct snd_ac97 * ac97
the ac97 instance
unsigned short reg
the register to change
unsigned short value
the value to set

Description

Compares the value with the register cache and updates the value only when the value is changed.

Return

1 if the value is changed, 0 if no change, or a negative code on failure.

int snd_ac97_update_bits(struct snd_ac97 * ac97, unsigned short reg, unsigned short mask, unsigned short value)

update the bits on the given register

Parameters

struct snd_ac97 * ac97
the ac97 instance
unsigned short reg
the register to change
unsigned short mask
the bit-mask to change
unsigned short value
the value to set

Description

Updates the masked-bits on the given register only when the value is changed.

Return

1 if the bits are changed, 0 if no change, or a negative code on failure.

const char * snd_ac97_get_short_name(struct snd_ac97 * ac97)

retrieve codec name

Parameters

struct snd_ac97 * ac97
the codec instance

Return

The short identifying name of the codec.

int snd_ac97_bus(struct snd_card * card, int num, struct snd_ac97_bus_ops * ops, void * private_data, struct snd_ac97_bus ** rbus)

create an AC97 bus component

Parameters

struct snd_card * card
the card instance
int num
the bus number
struct snd_ac97_bus_ops * ops
the bus callbacks table
void * private_data
private data pointer for the new instance
struct snd_ac97_bus ** rbus
the pointer to store the new AC97 bus instance.

Description

Creates an AC97 bus component. An struct snd_ac97_bus instance is newly allocated and initialized.

The ops table must include valid callbacks (at least read and write). The other callbacks, wait and reset, are not mandatory.

The clock is set to 48000. If another clock is needed, set (*rbus)->clock manually.

The AC97 bus instance is registered as a low-level device, so you don’t have to release it manually.

Return

Zero if successful, or a negative error code on failure.

int snd_ac97_mixer(struct snd_ac97_bus * bus, struct snd_ac97_template * template, struct snd_ac97 ** rac97)

create an Codec97 component

Parameters

struct snd_ac97_bus * bus
the AC97 bus which codec is attached to
struct snd_ac97_template * template
the template of ac97, including index, callbacks and the private data.
struct snd_ac97 ** rac97
the pointer to store the new ac97 instance.

Description

Creates an Codec97 component. An struct snd_ac97 instance is newly allocated and initialized from the template. The codec is then initialized by the standard procedure.

The template must include the codec number (num) and address (addr), and the private data (private_data).

The ac97 instance is registered as a low-level device, so you don’t have to release it manually.

Return

Zero if successful, or a negative error code on failure.

int snd_ac97_update_power(struct snd_ac97 * ac97, int reg, int powerup)

update the powerdown register

Parameters

struct snd_ac97 * ac97
the codec instance
int reg
the rate register, e.g. AC97_PCM_FRONT_DAC_RATE
int powerup
non-zero when power up the part

Description

Update the AC97 powerdown register bits of the given part.

Return

Zero.

void snd_ac97_suspend(struct snd_ac97 * ac97)

General suspend function for AC97 codec

Parameters

struct snd_ac97 * ac97
the ac97 instance

Description

Suspends the codec, power down the chip.

void snd_ac97_resume(struct snd_ac97 * ac97)

General resume function for AC97 codec

Parameters

struct snd_ac97 * ac97
the ac97 instance

Description

Do the standard resume procedure, power up and restoring the old register values.

int snd_ac97_tune_hardware(struct snd_ac97 * ac97, const struct ac97_quirk * quirk, const char * override)

tune up the hardware

Parameters

struct snd_ac97 * ac97
the ac97 instance
const struct ac97_quirk * quirk
quirk list
const char * override
explicit quirk value (overrides the list if non-NULL)

Description

Do some workaround for each pci device, such as renaming of the headphone (true line-out) control as “Master”. The quirk-list must be terminated with a zero-filled entry.

Return

Zero if successful, or a negative error code on failure.

int snd_ac97_set_rate(struct snd_ac97 * ac97, int reg, unsigned int rate)

change the rate of the given input/output.

Parameters

struct snd_ac97 * ac97
the ac97 instance
int reg
the register to change
unsigned int rate
the sample rate to set

Description

Changes the rate of the given input/output on the codec. If the codec doesn’t support VAR, the rate must be 48000 (except for SPDIF).

The valid registers are AC97_PMC_MIC_ADC_RATE, AC97_PCM_FRONT_DAC_RATE, AC97_PCM_LR_ADC_RATE. AC97_PCM_SURR_DAC_RATE and AC97_PCM_LFE_DAC_RATE are accepted if the codec supports them. AC97_SPDIF is accepted as a pseudo register to modify the SPDIF status bits.

Return

Zero if successful, or a negative error code on failure.

int snd_ac97_pcm_assign(struct snd_ac97_bus * bus, unsigned short pcms_count, const struct ac97_pcm * pcms)

assign AC97 slots to given PCM streams

Parameters

struct snd_ac97_bus * bus
the ac97 bus instance
unsigned short pcms_count
count of PCMs to be assigned
const struct ac97_pcm * pcms
PCMs to be assigned

Description

It assigns available AC97 slots for given PCMs. If none or only some slots are available, pcm->xxx.slots and pcm->xxx.rslots[] members are reduced and might be zero.

Return

Zero if successful, or a negative error code on failure.

int snd_ac97_pcm_open(struct ac97_pcm * pcm, unsigned int rate, enum ac97_pcm_cfg cfg, unsigned short slots)

opens the given AC97 pcm

Parameters

struct ac97_pcm * pcm
the ac97 pcm instance
unsigned int rate
rate in Hz, if codec does not support VRA, this value must be 48000Hz
enum ac97_pcm_cfg cfg
output stream characteristics
unsigned short slots
a subset of allocated slots (snd_ac97_pcm_assign) for this pcm

Description

It locks the specified slots and sets the given rate to AC97 registers.

Return

Zero if successful, or a negative error code on failure.

int snd_ac97_pcm_close(struct ac97_pcm * pcm)

closes the given AC97 pcm

Parameters

struct ac97_pcm * pcm
the ac97 pcm instance

Description

It frees the locked AC97 slots.

Return

Zero.

int snd_ac97_pcm_double_rate_rules(struct snd_pcm_runtime * runtime)

set double rate constraints

Parameters

struct snd_pcm_runtime * runtime
the runtime of the ac97 front playback pcm

Description

Installs the hardware constraint rules to prevent using double rates and more than two channels at the same time.

Return

Zero if successful, or a negative error code on failure.

Virtual Master Control API

struct snd_kcontrol * snd_ctl_make_virtual_master(char * name, const unsigned int * tlv)

Create a virtual master control

Parameters

char * name
name string of the control element to create
const unsigned int * tlv
optional TLV int array for dB information

Description

Creates a virtual master control with the given name string.

After creating a vmaster element, you can add the slave controls via snd_ctl_add_slave() or snd_ctl_add_slave_uncached().

The optional argument tlv can be used to specify the TLV information for dB scale of the master control. It should be a single element with #SNDRV_CTL_TLVT_DB_SCALE, #SNDRV_CTL_TLV_DB_MINMAX or #SNDRV_CTL_TLVT_DB_MINMAX_MUTE type, and should be the max 0dB.

Return

The created control element, or NULL for errors (ENOMEM).

int snd_ctl_add_vmaster_hook(struct snd_kcontrol * kcontrol, void (*hook) (void *private_data, int, void * private_data)

Add a hook to a vmaster control

Parameters

struct snd_kcontrol * kcontrol
vmaster kctl element
void (*)(void *private_data, int) hook
the hook function
void * private_data
the private_data pointer to be saved

Description

Adds the given hook to the vmaster control element so that it’s called at each time when the value is changed.

Return

Zero.

void snd_ctl_sync_vmaster(struct snd_kcontrol * kcontrol, bool hook_only)

Sync the vmaster slaves and hook

Parameters

struct snd_kcontrol * kcontrol
vmaster kctl element
bool hook_only
sync only the hook

Description

Forcibly call the put callback of each slave and call the hook function to synchronize with the current value of the given vmaster element. NOP when NULL is passed to kcontrol.

int snd_ctl_add_slave(struct snd_kcontrol * master, struct snd_kcontrol * slave)

Add a virtual slave control

Parameters

struct snd_kcontrol * master
vmaster element
struct snd_kcontrol * slave
slave element to add

Description

Add a virtual slave control to the given master element created via snd_ctl_create_virtual_master() beforehand.

All slaves must be the same type (returning the same information via info callback). The function doesn’t check it, so it’s your responsibility.

Also, some additional limitations: at most two channels, logarithmic volume control (dB level) thus no linear volume, master can only attenuate the volume without gain

Return

Zero if successful or a negative error code.

int snd_ctl_add_slave_uncached(struct snd_kcontrol * master, struct snd_kcontrol * slave)

Add a virtual slave control

Parameters

struct snd_kcontrol * master
vmaster element
struct snd_kcontrol * slave
slave element to add

Description

Add a virtual slave control to the given master. Unlike snd_ctl_add_slave(), the element added via this function is supposed to have volatile values, and get callback is called at each time queried from the master.

When the control peeks the hardware values directly and the value can be changed by other means than the put callback of the element, this function should be used to keep the value always up-to-date.

Return

Zero if successful or a negative error code.

MIDI API

Raw MIDI API

int snd_rawmidi_receive(struct snd_rawmidi_substream * substream, const unsigned char * buffer, int count)

receive the input data from the device

Parameters

struct snd_rawmidi_substream * substream
the rawmidi substream
const unsigned char * buffer
the buffer pointer
int count
the data size to read

Description

Reads the data from the internal buffer.

Return

The size of read data, or a negative error code on failure.

int snd_rawmidi_transmit_empty(struct snd_rawmidi_substream * substream)

check whether the output buffer is empty

Parameters

struct snd_rawmidi_substream * substream
the rawmidi substream

Return

1 if the internal output buffer is empty, 0 if not.

int __snd_rawmidi_transmit_peek(struct snd_rawmidi_substream * substream, unsigned char * buffer, int count)

copy data from the internal buffer

Parameters

struct snd_rawmidi_substream * substream
the rawmidi substream
unsigned char * buffer
the buffer pointer
int count
data size to transfer

Description

This is a variant of snd_rawmidi_transmit_peek() without spinlock.

int snd_rawmidi_transmit_peek(struct snd_rawmidi_substream * substream, unsigned char * buffer, int count)

copy data from the internal buffer

Parameters

struct snd_rawmidi_substream * substream
the rawmidi substream
unsigned char * buffer
the buffer pointer
int count
data size to transfer

Description

Copies data from the internal output buffer to the given buffer.

Call this in the interrupt handler when the midi output is ready, and call snd_rawmidi_transmit_ack() after the transmission is finished.

Return

The size of copied data, or a negative error code on failure.

int __snd_rawmidi_transmit_ack(struct snd_rawmidi_substream * substream, int count)

acknowledge the transmission

Parameters

struct snd_rawmidi_substream * substream
the rawmidi substream
int count
the transferred count

Description

This is a variant of __snd_rawmidi_transmit_ack() without spinlock.

int snd_rawmidi_transmit_ack(struct snd_rawmidi_substream * substream, int count)

acknowledge the transmission

Parameters

struct snd_rawmidi_substream * substream
the rawmidi substream
int count
the transferred count

Description

Advances the hardware pointer for the internal output buffer with the given size and updates the condition. Call after the transmission is finished.

Return

The advanced size if successful, or a negative error code on failure.

int snd_rawmidi_transmit(struct snd_rawmidi_substream * substream, unsigned char * buffer, int count)

copy from the buffer to the device

Parameters

struct snd_rawmidi_substream * substream
the rawmidi substream
unsigned char * buffer
the buffer pointer
int count
the data size to transfer

Description

Copies data from the buffer to the device and advances the pointer.

Return

The copied size if successful, or a negative error code on failure.

int snd_rawmidi_new(struct snd_card * card, char * id, int device, int output_count, int input_count, struct snd_rawmidi ** rrawmidi)

create a rawmidi instance

Parameters

struct snd_card * card
the card instance
char * id
the id string
int device
the device index
int output_count
the number of output streams
int input_count
the number of input streams
struct snd_rawmidi ** rrawmidi
the pointer to store the new rawmidi instance

Description

Creates a new rawmidi instance. Use snd_rawmidi_set_ops() to set the operators to the new instance.

Return

Zero if successful, or a negative error code on failure.

void snd_rawmidi_set_ops(struct snd_rawmidi * rmidi, int stream, struct snd_rawmidi_ops * ops)

set the rawmidi operators

Parameters

struct snd_rawmidi * rmidi
the rawmidi instance
int stream
the stream direction, SNDRV_RAWMIDI_STREAM_XXX
struct snd_rawmidi_ops * ops
the operator table

Description

Sets the rawmidi operators for the given stream direction.

MPU401-UART API

irqreturn_t snd_mpu401_uart_interrupt(int irq, void * dev_id)

generic MPU401-UART interrupt handler

Parameters

int irq
the irq number
void * dev_id
mpu401 instance

Description

Processes the interrupt for MPU401-UART i/o.

Return

IRQ_HANDLED if the interrupt was handled. IRQ_NONE otherwise.

irqreturn_t snd_mpu401_uart_interrupt_tx(int irq, void * dev_id)

generic MPU401-UART transmit irq handler

Parameters

int irq
the irq number
void * dev_id
mpu401 instance

Description

Processes the interrupt for MPU401-UART output.

Return

IRQ_HANDLED if the interrupt was handled. IRQ_NONE otherwise.

int snd_mpu401_uart_new(struct snd_card * card, int device, unsigned short hardware, unsigned long port, unsigned int info_flags, int irq, struct snd_rawmidi ** rrawmidi)

create an MPU401-UART instance

Parameters

struct snd_card * card
the card instance
int device
the device index, zero-based
unsigned short hardware
the hardware type, MPU401_HW_XXXX
unsigned long port
the base address of MPU401 port
unsigned int info_flags
bitflags MPU401_INFO_XXX
int irq
the ISA irq number, -1 if not to be allocated
struct snd_rawmidi ** rrawmidi
the pointer to store the new rawmidi instance

Description

Creates a new MPU-401 instance.

Note that the rawmidi instance is returned on the rrawmidi argument, not the mpu401 instance itself. To access to the mpu401 instance, cast from rawmidi->private_data (with struct snd_mpu401 magic-cast).

Return

Zero if successful, or a negative error code.

Proc Info API

Proc Info Interface

int snd_info_get_line(struct snd_info_buffer * buffer, char * line, int len)

read one line from the procfs buffer

Parameters

struct snd_info_buffer * buffer
the procfs buffer
char * line
the buffer to store
int len
the max. buffer size

Description

Reads one line from the buffer and stores the string.

Return

Zero if successful, or 1 if error or EOF.

const char * snd_info_get_str(char * dest, const char * src, int len)

parse a string token

Parameters

char * dest
the buffer to store the string token
const char * src
the original string
int len
the max. length of token - 1

Description

Parses the original string and copy a token to the given string buffer.

Return

The updated pointer of the original string so that it can be used for the next call.

struct snd_info_entry * snd_info_create_module_entry(struct module * module, const char * name, struct snd_info_entry * parent)

create an info entry for the given module

Parameters

struct module * module
the module pointer
const char * name
the file name
struct snd_info_entry * parent
the parent directory

Description

Creates a new info entry and assigns it to the given module.

Return

The pointer of the new instance, or NULL on failure.

struct snd_info_entry * snd_info_create_card_entry(struct snd_card * card, const char * name, struct snd_info_entry * parent)

create an info entry for the given card

Parameters

struct snd_card * card
the card instance
const char * name
the file name
struct snd_info_entry * parent
the parent directory

Description

Creates a new info entry and assigns it to the given card.

Return

The pointer of the new instance, or NULL on failure.

void snd_info_free_entry(struct snd_info_entry * entry)

release the info entry

Parameters

struct snd_info_entry * entry
the info entry

Description

Releases the info entry.

int snd_info_register(struct snd_info_entry * entry)

register the info entry

Parameters

struct snd_info_entry * entry
the info entry

Description

Registers the proc info entry.

Return

Zero if successful, or a negative error code on failure.

Compress Offload

Compress Offload API

int snd_compress_register(struct snd_compr * device)

register compressed device

Parameters

struct snd_compr * device
compressed device to register
struct snd_compressed_buffer

compressed buffer

Definition

struct snd_compressed_buffer {
  __u32 fragment_size;
  __u32 fragments;
};

Members

__u32 fragment_size
size of buffer fragment in bytes
__u32 fragments
number of such fragments
struct snd_compr_params

compressed stream params

Definition

struct snd_compr_params {
  struct snd_compressed_buffer buffer;
  struct snd_codec codec;
  __u8 no_wake_mode;
};

Members

struct snd_compressed_buffer buffer
buffer description
struct snd_codec codec
codec parameters
__u8 no_wake_mode
dont wake on fragment elapsed
struct snd_compr_tstamp

timestamp descriptor

Definition

struct snd_compr_tstamp {
  __u32 byte_offset;
  __u32 copied_total;
  __u32 pcm_frames;
  __u32 pcm_io_frames;
  __u32 sampling_rate;
};

Members

__u32 byte_offset
Byte offset in ring buffer to DSP
__u32 copied_total
Total number of bytes copied from/to ring buffer to/by DSP
__u32 pcm_frames
Frames decoded or encoded by DSP. This field will evolve by large steps and should only be used to monitor encoding/decoding progress. It shall not be used for timing estimates.
__u32 pcm_io_frames
Frames rendered or received by DSP into a mixer or an audio output/input. This field should be used for A/V sync or time estimates.
__u32 sampling_rate
sampling rate of audio
struct snd_compr_avail

avail descriptor

Definition

struct snd_compr_avail {
  __u64 avail;
  struct snd_compr_tstamp tstamp;
};

Members

__u64 avail
Number of bytes available in ring buffer for writing/reading
struct snd_compr_tstamp tstamp
timestamp information
struct snd_compr_caps

caps descriptor

Definition

struct snd_compr_caps {
  __u32 num_codecs;
  __u32 direction;
  __u32 min_fragment_size;
  __u32 max_fragment_size;
  __u32 min_fragments;
  __u32 max_fragments;
  __u32 codecs[MAX_NUM_CODECS];
  __u32 reserved[11];
};

Members

__u32 num_codecs
number of codecs supported
__u32 direction
direction supported. Of type snd_compr_direction
__u32 min_fragment_size
minimum fragment supported by DSP
__u32 max_fragment_size
maximum fragment supported by DSP
__u32 min_fragments
min fragments supported by DSP
__u32 max_fragments
max fragments supported by DSP
__u32 codecs[MAX_NUM_CODECS]
pointer to array of codecs
__u32 reserved[11]
reserved field
struct snd_compr_codec_caps

query capability of codec

Definition

struct snd_compr_codec_caps {
  __u32 codec;
  __u32 num_descriptors;
  struct snd_codec_desc descriptor[MAX_NUM_CODEC_DESCRIPTORS];
};

Members

__u32 codec
codec for which capability is queried
__u32 num_descriptors
number of codec descriptors
struct snd_codec_desc descriptor[MAX_NUM_CODEC_DESCRIPTORS]
array of codec capability descriptor
enum sndrv_compress_encoder

Constants

SNDRV_COMPRESS_ENCODER_PADDING
no of samples appended by the encoder at the end of the track
SNDRV_COMPRESS_ENCODER_DELAY
no of samples inserted by the encoder at the beginning of the track
struct snd_compr_metadata

compressed stream metadata

Definition

struct snd_compr_metadata {
  __u32 key;
  __u32 value[8];
};

Members

__u32 key
key id
__u32 value[8]
key value
SNDRV_COMPRESS_IOCTL_VERSION()

Parameters

Description

SNDRV_COMPRESS_GET_CAPS: Query capability of DSP SNDRV_COMPRESS_GET_CODEC_CAPS: Query capability of a codec SNDRV_COMPRESS_SET_PARAMS: Set codec and stream parameters

Note

only codec params can be changed runtime and stream params cant be SNDRV_COMPRESS_GET_PARAMS: Query codec params SNDRV_COMPRESS_TSTAMP: get the current timestamp value SNDRV_COMPRESS_AVAIL: get the current buffer avail value. This also queries the tstamp properties SNDRV_COMPRESS_PAUSE: Pause the running stream SNDRV_COMPRESS_RESUME: resume a paused stream SNDRV_COMPRESS_START: Start a stream SNDRV_COMPRESS_STOP: stop a running stream, discarding ring buffer content and the buffers currently with DSP SNDRV_COMPRESS_DRAIN: Play till end of buffers and stop after that SNDRV_COMPRESS_IOCTL_VERSION: Query the API version

struct snd_enc_vorbis

Definition

struct snd_enc_vorbis {
  __s32 quality;
  __u32 managed;
  __u32 max_bit_rate;
  __u32 min_bit_rate;
  __u32 downmix;
};

Members

__s32 quality
Sets encoding quality to n, between -1 (low) and 10 (high). In the default mode of operation, the quality level is 3. Normal quality range is 0 - 10.
__u32 managed
Boolean. Set bitrate management mode. This turns off the normal VBR encoding, but allows hard or soft bitrate constraints to be enforced by the encoder. This mode can be slower, and may also be lower quality. It is primarily useful for streaming.
__u32 max_bit_rate
Enabled only if managed is TRUE
__u32 min_bit_rate
Enabled only if managed is TRUE
__u32 downmix
Boolean. Downmix input from stereo to mono (has no effect on non-stereo streams). Useful for lower-bitrate encoding.

Description

These options were extracted from the OpenMAX IL spec and Gstreamer vorbisenc properties

For best quality users should specify VBR mode and set quality levels.

struct snd_enc_real

Definition

struct snd_enc_real {
  __u32 quant_bits;
  __u32 start_region;
  __u32 num_regions;
};

Members

__u32 quant_bits
number of coupling quantization bits in the stream
__u32 start_region
coupling start region in the stream
__u32 num_regions
number of regions value

Description

These options were extracted from the OpenMAX IL spec

struct snd_enc_flac

Definition

struct snd_enc_flac {
  __u32 num;
  __u32 gain;
};

Members

__u32 num
serial number, valid only for OGG formats needs to be set by application
__u32 gain
Add replay gain tags

Description

These options were extracted from the FLAC online documentation at http://flac.sourceforge.net/documentation_tools_flac.html

To make the API simpler, it is assumed that the user will select quality profiles. Additional options that affect encoding quality and speed can be added at a later stage if needed.

By default the Subset format is used by encoders.

TAGS such as pictures, etc, cannot be handled by an offloaded encoder and are not supported in this API.

struct snd_compr_runtime

Definition

struct snd_compr_runtime {
  snd_pcm_state_t state;
  struct snd_compr_ops * ops;
  void * buffer;
  u64 buffer_size;
  u32 fragment_size;
  u32 fragments;
  u64 total_bytes_available;
  u64 total_bytes_transferred;
  wait_queue_head_t sleep;
  void * private_data;
};

Members

snd_pcm_state_t state
stream state
struct snd_compr_ops * ops
pointer to DSP callbacks
void * buffer
pointer to kernel buffer, valid only when not in mmap mode or DSP doesn’t implement copy
u64 buffer_size
size of the above buffer
u32 fragment_size
size of buffer fragment in bytes
u32 fragments
number of such fragments
u64 total_bytes_available
cumulative number of bytes made available in the ring buffer
u64 total_bytes_transferred
cumulative bytes transferred by offload DSP
wait_queue_head_t sleep
poll sleep
void * private_data
driver private data pointer
struct snd_compr_stream

Definition

struct snd_compr_stream {
  const char * name;
  struct snd_compr_ops * ops;
  struct snd_compr_runtime * runtime;
  struct snd_compr * device;
  enum snd_compr_direction direction;
  bool metadata_set;
  bool next_track;
  void * private_data;
};

Members

const char * name
device name
struct snd_compr_ops * ops
pointer to DSP callbacks
struct snd_compr_runtime * runtime
pointer to runtime structure
struct snd_compr * device
device pointer
enum snd_compr_direction direction
stream direction, playback/recording
bool metadata_set
metadata set flag, true when set
bool next_track
has userspace signal next track transition, true when set
void * private_data
pointer to DSP private data
struct snd_compr_ops

Definition

struct snd_compr_ops {
  int (* open) (struct snd_compr_stream *stream);
  int (* free) (struct snd_compr_stream *stream);
  int (* set_params) (struct snd_compr_stream *stream,struct snd_compr_params *params);
  int (* get_params) (struct snd_compr_stream *stream,struct snd_codec *params);
  int (* set_metadata) (struct snd_compr_stream *stream,struct snd_compr_metadata *metadata);
  int (* get_metadata) (struct snd_compr_stream *stream,struct snd_compr_metadata *metadata);
  int (* trigger) (struct snd_compr_stream *stream, int cmd);
  int (* pointer) (struct snd_compr_stream *stream,struct snd_compr_tstamp *tstamp);
  int (* copy) (struct snd_compr_stream *stream, char __user *buf,size_t count);
  int (* mmap) (struct snd_compr_stream *stream,struct vm_area_struct *vma);
  int (* ack) (struct snd_compr_stream *stream, size_t bytes);
  int (* get_caps) (struct snd_compr_stream *stream,struct snd_compr_caps *caps);
  int (* get_codec_caps) (struct snd_compr_stream *stream,struct snd_compr_codec_caps *codec);
};

Members

int (*)(struct snd_compr_stream *stream) open
Open the compressed stream This callback is mandatory and shall keep dsp ready to receive the stream parameter
int (*)(struct snd_compr_stream *stream) free
Close the compressed stream, mandatory
int (*)(struct snd_compr_stream *stream,struct snd_compr_params *params) set_params
Sets the compressed stream parameters, mandatory This can be called in during stream creation only to set codec params and the stream properties
int (*)(struct snd_compr_stream *stream,struct snd_codec *params) get_params
retrieve the codec parameters, mandatory
int (*)(struct snd_compr_stream *stream,struct snd_compr_metadata *metadata) set_metadata
Set the metadata values for a stream
int (*)(struct snd_compr_stream *stream,struct snd_compr_metadata *metadata) get_metadata
retrieves the requested metadata values from stream
int (*)(struct snd_compr_stream *stream, int cmd) trigger
Trigger operations like start, pause, resume, drain, stop. This callback is mandatory
int (*)(struct snd_compr_stream *stream,struct snd_compr_tstamp *tstamp) pointer
Retrieve current h/w pointer information. Mandatory
int (*)(struct snd_compr_stream *stream, char __user *buf,size_t count) copy
Copy the compressed data to/from userspace, Optional Can’t be implemented if DSP supports mmap
int (*)(struct snd_compr_stream *stream,struct vm_area_struct *vma) mmap
DSP mmap method to mmap DSP memory
int (*)(struct snd_compr_stream *stream, size_t bytes) ack
Ack for DSP when data is written to audio buffer, Optional Not valid if copy is implemented
int (*) (struct snd_compr_stream *stream,struct snd_compr_caps *caps) get_caps
Retrieve DSP capabilities, mandatory
int (*) (struct snd_compr_stream *stream,struct snd_compr_codec_caps *codec) get_codec_caps
Retrieve capabilities for a specific codec, mandatory
struct snd_compr

Definition

struct snd_compr {
  const char * name;
  struct device dev;
  struct snd_compr_ops * ops;
  void * private_data;
  struct snd_card * card;
  unsigned int direction;
  struct mutex lock;
  int device;
#ifdef CONFIG_SND_VERBOSE_PROCFS
#endif
};

Members

const char * name
DSP device name
struct device dev
associated device instance
struct snd_compr_ops * ops
pointer to DSP callbacks
void * private_data
pointer to DSP pvt data
struct snd_card * card
sound card pointer
unsigned int direction
Playback or capture direction
struct mutex lock
device lock
int device
device id

ASoC

ASoC Core API

struct snd_soc_jack_pin

Describes a pin to update based on jack detection

Definition

struct snd_soc_jack_pin {
  struct list_head list;
  const char * pin;
  int mask;
  bool invert;
};

Members

struct list_head list
internal list entry
const char * pin
name of the pin to update
int mask
bits to check for in reported jack status
bool invert
if non-zero then pin is enabled when status is not reported
struct snd_soc_jack_zone

Describes voltage zones of jack detection

Definition

struct snd_soc_jack_zone {
  unsigned int min_mv;
  unsigned int max_mv;
  unsigned int jack_type;
  unsigned int debounce_time;
  struct list_head list;
};

Members

unsigned int min_mv
start voltage in mv
unsigned int max_mv
end voltage in mv
unsigned int jack_type
type of jack that is expected for this voltage
unsigned int debounce_time
debounce_time for jack, codec driver should wait for this duration before reading the adc for voltages
struct list_head list
internal list entry
struct snd_soc_jack_gpio

Describes a gpio pin for jack detection

Definition

struct snd_soc_jack_gpio {
  unsigned int gpio;
  unsigned int idx;
  struct device * gpiod_dev;
  const char * name;
  int report;
  int invert;
  int debounce_time;
  bool wake;
  int (* jack_status_check) (void *data);
};

Members

unsigned int gpio
legacy gpio number
unsigned int idx
gpio descriptor index within the function of the GPIO consumer device
struct device * gpiod_dev
GPIO consumer device
const char * name
gpio name. Also as connection ID for the GPIO consumer device function name lookup
int report
value to report when jack detected
int invert
report presence in low state
int debounce_time
debounce time in ms
bool wake
enable as wake source
int (*)(void *data) jack_status_check
callback function which overrides the detection to provide more complex checks (eg, reading an ADC).
struct snd_soc_codec * snd_soc_component_to_codec(struct snd_soc_component * component)

Casts a component to the CODEC it is embedded in

Parameters

struct snd_soc_component * component
The component to cast to a CODEC

Description

This function must only be used on components that are known to be CODECs. Otherwise the behavior is undefined.

struct snd_soc_platform * snd_soc_component_to_platform(struct snd_soc_component * component)

Casts a component to the platform it is embedded in

Parameters

struct snd_soc_component * component
The component to cast to a platform

Description

This function must only be used on components that are known to be platforms. Otherwise the behavior is undefined.

struct snd_soc_component * snd_soc_dapm_to_component(struct snd_soc_dapm_context * dapm)

Casts a DAPM context to the component it is embedded in

Parameters

struct snd_soc_dapm_context * dapm
The DAPM context to cast to the component

Description

This function must only be used on DAPM contexts that are known to be part of a component (e.g. in a component driver). Otherwise the behavior is undefined.

struct snd_soc_codec * snd_soc_dapm_to_codec(struct snd_soc_dapm_context * dapm)

Casts a DAPM context to the CODEC it is embedded in

Parameters

struct snd_soc_dapm_context * dapm
The DAPM context to cast to the CODEC

Description

This function must only be used on DAPM contexts that are known to be part of a CODEC (e.g. in a CODEC driver). Otherwise the behavior is undefined.

struct snd_soc_platform * snd_soc_dapm_to_platform(struct snd_soc_dapm_context * dapm)

Casts a DAPM context to the platform it is embedded in

Parameters

struct snd_soc_dapm_context * dapm
The DAPM context to cast to the platform.

Description

This function must only be used on DAPM contexts that are known to be part of a platform (e.g. in a platform driver). Otherwise the behavior is undefined.

struct snd_soc_dapm_context * snd_soc_component_get_dapm(struct snd_soc_component * component)

Returns the DAPM context associated with a component

Parameters

struct snd_soc_component * component
The component for which to get the DAPM context
struct snd_soc_dapm_context * snd_soc_codec_get_dapm(struct snd_soc_codec * codec)

Returns the DAPM context for the CODEC

Parameters

struct snd_soc_codec * codec
The CODEC for which to get the DAPM context

Note

Use this function instead of directly accessing the CODEC’s dapm field

void snd_soc_codec_init_bias_level(struct snd_soc_codec * codec, enum snd_soc_bias_level level)

Initialize CODEC DAPM bias level

Parameters

struct snd_soc_codec * codec
The CODEC for which to initialize the DAPM bias level
enum snd_soc_bias_level level
The DAPM level to initialize to

Description

Initializes the CODEC DAPM bias level. See snd_soc_dapm_init_bias_level().

enum snd_soc_bias_level snd_soc_codec_get_bias_level(struct snd_soc_codec * codec)

Get current CODEC DAPM bias level

Parameters

struct snd_soc_codec * codec
The CODEC for which to get the DAPM bias level

Return

The current DAPM bias level of the CODEC.

int snd_soc_codec_force_bias_level(struct snd_soc_codec * codec, enum snd_soc_bias_level level)

Set the CODEC DAPM bias level

Parameters

struct snd_soc_codec * codec
The CODEC for which to set the level
enum snd_soc_bias_level level
The level to set to

Description

Forces the CODEC bias level to a specific state. See snd_soc_dapm_force_bias_level().

struct snd_soc_codec * snd_soc_dapm_kcontrol_codec(struct snd_kcontrol * kcontrol)

Returns the codec associated to a kcontrol

Parameters

struct snd_kcontrol * kcontrol
The kcontrol

Description

This function must only be used on DAPM contexts that are known to be part of a CODEC (e.g. in a CODEC driver). Otherwise the behavior is undefined.

int snd_soc_cache_sync(struct snd_soc_codec * codec)

Sync the register cache with the hardware

Parameters

struct snd_soc_codec * codec
CODEC to sync

Note

This function will call regcache_sync()

void snd_soc_codec_init_regmap(struct snd_soc_codec * codec, struct regmap * regmap)

Initialize regmap instance for the CODEC

Parameters

struct snd_soc_codec * codec
The CODEC for which to initialize the regmap instance
struct regmap * regmap
The regmap instance that should be used by the CODEC

Description

This function allows deferred assignment of the regmap instance that is associated with the CODEC. Only use this if the regmap instance is not yet ready when the CODEC is registered. The function must also be called before the first IO attempt of the CODEC.

void snd_soc_codec_exit_regmap(struct snd_soc_codec * codec)

De-initialize regmap instance for the CODEC

Parameters

struct snd_soc_codec * codec
The CODEC for which to de-initialize the regmap instance

Description

Calls regmap_exit() on the regmap instance associated to the CODEC and removes the regmap instance from the CODEC.

This function should only be used if snd_soc_codec_init_regmap() was used to initialize the regmap instance.

struct snd_soc_component * snd_soc_kcontrol_component(struct snd_kcontrol * kcontrol)

Returns the component that registered the control

Parameters

struct snd_kcontrol * kcontrol
The control for which to get the component

Note

This function will work correctly if the control has been registered for a component. Either with snd_soc_add_codec_controls() or snd_soc_add_platform_controls() or via table based setup for either a CODEC, a platform or component driver. Otherwise the behavior is undefined.

struct snd_soc_codec * snd_soc_kcontrol_codec(struct snd_kcontrol * kcontrol)

Returns the CODEC that registered the control

Parameters

struct snd_kcontrol * kcontrol
The control for which to get the CODEC

Note

This function will only work correctly if the control has been registered with snd_soc_add_codec_controls() or via table based setup of snd_soc_codec_driver. Otherwise the behavior is undefined.

struct snd_soc_platform * snd_soc_kcontrol_platform(struct snd_kcontrol * kcontrol)

Returns the platform that registered the control

Parameters

struct snd_kcontrol * kcontrol
The control for which to get the platform

Note

This function will only work correctly if the control has been registered with snd_soc_add_platform_controls() or via table based setup of a snd_soc_platform_driver. Otherwise the behavior is undefined.

struct snd_soc_dai * snd_soc_find_dai(const struct snd_soc_dai_link_component * dlc)

Find a registered DAI

Parameters

const struct snd_soc_dai_link_component * dlc
name of the DAI and optional component info to match

Description

This function will search all regsitered components and their DAIs to find the DAI of the same name. The component’s of_node and name should also match if being specified.

Return

pointer of DAI, or NULL if not found.

Add a DAI link dynamically

Parameters

struct snd_soc_card * card
The ASoC card to which the DAI link is added
struct snd_soc_dai_link * dai_link
The new DAI link to add

Description

This function adds a DAI link to the ASoC card’s link list.

Note

Topology can use this API to add DAI links when probing the topology component. And machine drivers can still define static DAI links in dai_link array.

Remove a DAI link from the list

Parameters

struct snd_soc_card * card
The ASoC card that owns the link
struct snd_soc_dai_link * dai_link
The DAI link to remove

Description

This function removes a DAI link from the ASoC card’s link list.

For DAI links previously added by topology, topology should remove them by using the dobj embedded in the link.

int snd_soc_runtime_set_dai_fmt(struct snd_soc_pcm_runtime * rtd, unsigned int dai_fmt)

Change DAI link format for a ASoC runtime

Parameters

struct snd_soc_pcm_runtime * rtd
The runtime for which the DAI link format should be changed
unsigned int dai_fmt
The new DAI link format

Description

This function updates the DAI link format for all DAIs connected to the DAI link for the specified runtime.

Note

For setups with a static format set the dai_fmt field in the corresponding snd_dai_link struct instead of using this function.

Returns 0 on success, otherwise a negative error code.

struct snd_kcontrol * snd_soc_cnew(const struct snd_kcontrol_new * _template, void * data, const char * long_name, const char * prefix)

create new control

Parameters

const struct snd_kcontrol_new * _template
control template
void * data
control private data
const char * long_name
control long name
const char * prefix
control name prefix

Description

Create a new mixer control from a template control.

Returns 0 for success, else error.

int snd_soc_add_component_controls(struct snd_soc_component * component, const struct snd_kcontrol_new * controls, unsigned int num_controls)

Add an array of controls to a component.

Parameters

struct snd_soc_component * component
Component to add controls to
const struct snd_kcontrol_new * controls
Array of controls to add
unsigned int num_controls
Number of elements in the array

Return

0 for success, else error.

int snd_soc_add_codec_controls(struct snd_soc_codec * codec, const struct snd_kcontrol_new * controls, unsigned int num_controls)

add an array of controls to a codec. Convenience function to add a list of controls. Many codecs were duplicating this code.

Parameters

struct snd_soc_codec * codec
codec to add controls to
const struct snd_kcontrol_new * controls
array of controls to add
unsigned int num_controls
number of elements in the array

Description

Return 0 for success, else error.

int snd_soc_add_platform_controls(struct snd_soc_platform * platform, const struct snd_kcontrol_new * controls, unsigned int num_controls)

add an array of controls to a platform. Convenience function to add a list of controls.

Parameters

struct snd_soc_platform * platform
platform to add controls to
const struct snd_kcontrol_new * controls
array of controls to add
unsigned int num_controls
number of elements in the array

Description

Return 0 for success, else error.

int snd_soc_add_card_controls(struct snd_soc_card * soc_card, const struct snd_kcontrol_new * controls, int num_controls)

add an array of controls to a SoC card. Convenience function to add a list of controls.

Parameters

struct snd_soc_card * soc_card
SoC card to add controls to
const struct snd_kcontrol_new * controls
array of controls to add
int num_controls
number of elements in the array

Description

Return 0 for success, else error.

int snd_soc_add_dai_controls(struct snd_soc_dai * dai, const struct snd_kcontrol_new * controls, int num_controls)

add an array of controls to a DAI. Convienience function to add a list of controls.

Parameters

struct snd_soc_dai * dai
DAI to add controls to
const struct snd_kcontrol_new * controls
array of controls to add
int num_controls
number of elements in the array

Description

Return 0 for success, else error.

int snd_soc_dai_set_sysclk(struct snd_soc_dai * dai, int clk_id, unsigned int freq, int dir)

configure DAI system or master clock.

Parameters

struct snd_soc_dai * dai
DAI
int clk_id
DAI specific clock ID
unsigned int freq
new clock frequency in Hz
int dir
new clock direction - input/output.

Description

Configures the DAI master (MCLK) or system (SYSCLK) clocking.

int snd_soc_codec_set_sysclk(struct snd_soc_codec * codec, int clk_id, int source, unsigned int freq, int dir)

configure CODEC system or master clock.

Parameters

struct snd_soc_codec * codec
CODEC
int clk_id
DAI specific clock ID
int source
Source for the clock
unsigned int freq
new clock frequency in Hz
int dir
new clock direction - input/output.

Description

Configures the CODEC master (MCLK) or system (SYSCLK) clocking.

int snd_soc_dai_set_clkdiv(struct snd_soc_dai * dai, int div_id, int div)

configure DAI clock dividers.

Parameters

struct snd_soc_dai * dai
DAI
int div_id
DAI specific clock divider ID
int div
new clock divisor.

Description

Configures the clock dividers. This is used to derive the best DAI bit and frame clocks from the system or master clock. It’s best to set the DAI bit and frame clocks as low as possible to save system power.

int snd_soc_dai_set_pll(struct snd_soc_dai * dai, int pll_id, int source, unsigned int freq_in, unsigned int freq_out)

configure DAI PLL.

Parameters

struct snd_soc_dai * dai
DAI
int pll_id
DAI specific PLL ID
int source
DAI specific source for the PLL
unsigned int freq_in
PLL input clock frequency in Hz
unsigned int freq_out
requested PLL output clock frequency in Hz

Description

Configures and enables PLL to generate output clock based on input clock.

int snd_soc_dai_set_bclk_ratio(struct snd_soc_dai * dai, unsigned int ratio)

configure BCLK to sample rate ratio.

Parameters

struct snd_soc_dai * dai
DAI
unsigned int ratio
Ratio of BCLK to Sample rate.

Description

Configures the DAI for a preset BCLK to sample rate ratio.

int snd_soc_dai_set_fmt(struct snd_soc_dai * dai, unsigned int fmt)

configure DAI hardware audio format.

Parameters

struct snd_soc_dai * dai
DAI
unsigned int fmt
SND_SOC_DAIFMT_ format value.

Description

Configures the DAI hardware format and clocking.

int snd_soc_dai_set_tdm_slot(struct snd_soc_dai * dai, unsigned int tx_mask, unsigned int rx_mask, int slots, int slot_width)

Configures a DAI for TDM operation

Parameters

struct snd_soc_dai * dai
The DAI to configure
unsigned int tx_mask
bitmask representing active TX slots.
unsigned int rx_mask
bitmask representing active RX slots.
int slots
Number of slots in use.
int slot_width
Width in bits for each slot.

Description

This function configures the specified DAI for TDM operation. slot contains the total number of slots of the TDM stream and slot_with the width of each slot in bit clock cycles. tx_mask and rx_mask are bitmasks specifying the active slots of the TDM stream for the specified DAI, i.e. which slots the DAI should write to or read from. If a bit is set the corresponding slot is active, if a bit is cleared the corresponding slot is inactive. Bit 0 maps to the first slot, bit 1 to the second slot and so on. The first active slot maps to the first channel of the DAI, the second active slot to the second channel and so on.

TDM mode can be disabled by passing 0 for slots. In this case tx_mask, rx_mask and slot_width will be ignored.

Returns 0 on success, a negative error code otherwise.

int snd_soc_dai_set_channel_map(struct snd_soc_dai * dai, unsigned int tx_num, unsigned int * tx_slot, unsigned int rx_num, unsigned int * rx_slot)

configure DAI audio channel map

Parameters

struct snd_soc_dai * dai
DAI
unsigned int tx_num
how many TX channels
unsigned int * tx_slot
pointer to an array which imply the TX slot number channel 0~num-1 uses
unsigned int rx_num
how many RX channels
unsigned int * rx_slot
pointer to an array which imply the RX slot number channel 0~num-1 uses

Description

configure the relationship between channel number and TDM slot number.

int snd_soc_dai_set_tristate(struct snd_soc_dai * dai, int tristate)

configure DAI system or master clock.

Parameters

struct snd_soc_dai * dai
DAI
int tristate
tristate enable

Description

Tristates the DAI so that others can use it.

int snd_soc_dai_digital_mute(struct snd_soc_dai * dai, int mute, int direction)

configure DAI system or master clock.

Parameters

struct snd_soc_dai * dai
DAI
int mute
mute enable
int direction
stream to mute

Description

Mutes the DAI DAC.

int snd_soc_register_card(struct snd_soc_card * card)

Register a card with the ASoC core

Parameters

struct snd_soc_card * card
Card to register
int snd_soc_unregister_card(struct snd_soc_card * card)

Unregister a card with the ASoC core

Parameters

struct snd_soc_card * card
Card to unregister
int snd_soc_register_dai(struct snd_soc_component * component, struct snd_soc_dai_driver * dai_drv)

Register a DAI dynamically & create its widgets

Parameters

struct snd_soc_component * component
The component the DAIs are registered for
struct snd_soc_dai_driver * dai_drv
DAI driver to use for the DAI

Description

Topology can use this API to register DAIs when probing a component. These DAIs’s widgets will be freed in the card cleanup and the DAIs will be freed in the component cleanup.

void snd_soc_component_init_regmap(struct snd_soc_component * component, struct regmap * regmap)

Initialize regmap instance for the component

Parameters

struct snd_soc_component * component
The component for which to initialize the regmap instance
struct regmap * regmap
The regmap instance that should be used by the component

Description

This function allows deferred assignment of the regmap instance that is associated with the component. Only use this if the regmap instance is not yet ready when the component is registered. The function must also be called before the first IO attempt of the component.

void snd_soc_component_exit_regmap(struct snd_soc_component * component)

De-initialize regmap instance for the component

Parameters

struct snd_soc_component * component
The component for which to de-initialize the regmap instance

Description

Calls regmap_exit() on the regmap instance associated to the component and removes the regmap instance from the component.

This function should only be used if snd_soc_component_init_regmap() was used to initialize the regmap instance.

void snd_soc_unregister_component(struct device * dev)

Unregister a component from the ASoC core

Parameters

struct device * dev
The device to unregister
int snd_soc_add_platform(struct device * dev, struct snd_soc_platform * platform, const struct snd_soc_platform_driver * platform_drv)

Add a platform to the ASoC core

Parameters

struct device * dev
The parent device for the platform
struct snd_soc_platform * platform
The platform to add
const struct snd_soc_platform_driver * platform_drv
The driver for the platform
int snd_soc_register_platform(struct device * dev, const struct snd_soc_platform_driver * platform_drv)

Register a platform with the ASoC core

Parameters

struct device * dev
The device for the platform
const struct snd_soc_platform_driver * platform_drv
The driver for the platform
void snd_soc_remove_platform(struct snd_soc_platform * platform)

Remove a platform from the ASoC core

Parameters

struct snd_soc_platform * platform
the platform to remove
void snd_soc_unregister_platform(struct device * dev)

Unregister a platform from the ASoC core

Parameters

struct device * dev
platform to unregister
int snd_soc_register_codec(struct device * dev, const struct snd_soc_codec_driver * codec_drv, struct snd_soc_dai_driver * dai_drv, int num_dai)

Register a codec with the ASoC core

Parameters

struct device * dev
The parent device for this codec
const struct snd_soc_codec_driver * codec_drv
Codec driver
struct snd_soc_dai_driver * dai_drv
The associated DAI driver
int num_dai
Number of DAIs
void snd_soc_unregister_codec(struct device * dev)

Unregister a codec from the ASoC core

Parameters

struct device * dev
codec to unregister
int devm_snd_soc_register_component(struct device * dev, const struct snd_soc_component_driver * cmpnt_drv, struct snd_soc_dai_driver * dai_drv, int num_dai)

resource managed component registration

Parameters

struct device * dev
Device used to manage component
const struct snd_soc_component_driver * cmpnt_drv
Component driver
struct snd_soc_dai_driver * dai_drv
DAI driver
int num_dai
Number of DAIs to register

Description

Register a component with automatic unregistration when the device is unregistered.

int devm_snd_soc_register_platform(struct device * dev, const struct snd_soc_platform_driver * platform_drv)

resource managed platform registration

Parameters

struct device * dev
Device used to manage platform
const struct snd_soc_platform_driver * platform_drv
platform to register

Description

Register a platform driver with automatic unregistration when the device is unregistered.

int devm_snd_soc_register_card(struct device * dev, struct snd_soc_card * card)

resource managed card registration

Parameters

struct device * dev
Device used to manage card
struct snd_soc_card * card
Card to register

Description

Register a card with automatic unregistration when the device is unregistered.

int devm_snd_dmaengine_pcm_register(struct device * dev, const struct snd_dmaengine_pcm_config * config, unsigned int flags)

resource managed dmaengine PCM registration

Parameters

struct device * dev
The parent device for the PCM device
const struct snd_dmaengine_pcm_config * config
Platform specific PCM configuration
unsigned int flags
Platform specific quirks

Description

Register a dmaengine based PCM device with automatic unregistration when the device is unregistered.

int snd_soc_component_read(struct snd_soc_component * component, unsigned int reg, unsigned int * val)

Read register value

Parameters

struct snd_soc_component * component
Component to read from
unsigned int reg
Register to read
unsigned int * val
Pointer to where the read value is stored

Return

0 on success, a negative error code otherwise.

int snd_soc_component_write(struct snd_soc_component * component, unsigned int reg, unsigned int val)

Write register value

Parameters

struct snd_soc_component * component
Component to write to
unsigned int reg
Register to write
unsigned int val
Value to write to the register

Return

0 on success, a negative error code otherwise.

int snd_soc_component_update_bits(struct snd_soc_component * component, unsigned int reg, unsigned int mask, unsigned int val)

Perform read/modify/write cycle

Parameters

struct snd_soc_component * component
Component to update
unsigned int reg
Register to update
unsigned int mask
Mask that specifies which bits to update
unsigned int val
New value for the bits specified by mask

Return

1 if the operation was successful and the value of the register changed, 0 if the operation was successful, but the value did not change. Returns a negative error code otherwise.

int snd_soc_component_update_bits_async(struct snd_soc_component * component, unsigned int reg, unsigned int mask, unsigned int val)

Perform asynchronous read/modify/write cycle

Parameters

struct snd_soc_component * component
Component to update
unsigned int reg
Register to update
unsigned int mask
Mask that specifies which bits to update
unsigned int val
New value for the bits specified by mask

Description

This function is similar to snd_soc_component_update_bits(), but the update operation is scheduled asynchronously. This means it may not be completed when the function returns. To make sure that all scheduled updates have been completed snd_soc_component_async_complete() must be called.

Return

1 if the operation was successful and the value of the register changed, 0 if the operation was successful, but the value did not change. Returns a negative error code otherwise.

void snd_soc_component_async_complete(struct snd_soc_component * component)

Ensure asynchronous I/O has completed

Parameters

struct snd_soc_component * component
Component for which to wait

Description

This function blocks until all asynchronous I/O which has previously been scheduled using snd_soc_component_update_bits_async() has completed.

int snd_soc_component_test_bits(struct snd_soc_component * component, unsigned int reg, unsigned int mask, unsigned int value)

Test register for change

Parameters

struct snd_soc_component * component
component
unsigned int reg
Register to test
unsigned int mask
Mask that specifies which bits to test
unsigned int value
Value to test against

Description

Tests a register with a new value and checks if the new value is different from the old value.

Return

1 for change, otherwise 0.

int snd_soc_update_bits(struct snd_soc_codec * codec, unsigned int reg, unsigned int mask, unsigned int value)

update codec register bits

Parameters

struct snd_soc_codec * codec
audio codec
unsigned int reg
codec register
unsigned int mask
register mask
unsigned int value
new value

Description

Writes new register value.

Returns 1 for change, 0 for no change, or negative error code.

int snd_soc_test_bits(struct snd_soc_codec * codec, unsigned int reg, unsigned int mask, unsigned int value)

test register for change

Parameters

struct snd_soc_codec * codec
audio codec
unsigned int reg
codec register
unsigned int mask
register mask
unsigned int value
new value

Description

Tests a register with a new value and checks if the new value is different from the old value.

Returns 1 for change else 0.

int snd_soc_set_runtime_hwparams(struct snd_pcm_substream * substream, const struct snd_pcm_hardware * hw)

set the runtime hardware parameters

Parameters

struct snd_pcm_substream * substream
the pcm substream
const struct snd_pcm_hardware * hw
the hardware parameters

Description

Sets the substream runtime hardware parameters.

int snd_soc_info_enum_double(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_info * uinfo)

enumerated double mixer info callback

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_info * uinfo
control element information

Description

Callback to provide information about a double enumerated mixer control.

Returns 0 for success.

int snd_soc_get_enum_double(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

enumerated double mixer get callback

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback to get the value of a double enumerated mixer.

Returns 0 for success.

int snd_soc_put_enum_double(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

enumerated double mixer put callback

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback to set the value of a double enumerated mixer.

Returns 0 for success.

int snd_soc_info_volsw(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_info * uinfo)

single mixer info callback

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_info * uinfo
control element information

Description

Callback to provide information about a single mixer control, or a double mixer control that spans 2 registers.

Returns 0 for success.

int snd_soc_info_volsw_sx(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_info * uinfo)

Mixer info callback for SX TLV controls

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_info * uinfo
control element information

Description

Callback to provide information about a single mixer control, or a double mixer control that spans 2 registers of the SX TLV type. SX TLV controls have a range that represents both positive and negative values either side of zero but without a sign bit.

Returns 0 for success.

int snd_soc_get_volsw(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

single mixer get callback

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback to get the value of a single mixer control, or a double mixer control that spans 2 registers.

Returns 0 for success.

int snd_soc_put_volsw(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

single mixer put callback

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback to set the value of a single mixer control, or a double mixer control that spans 2 registers.

Returns 0 for success.

int snd_soc_get_volsw_sx(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

single mixer get callback

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback to get the value of a single mixer control, or a double mixer control that spans 2 registers.

Returns 0 for success.

int snd_soc_put_volsw_sx(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

double mixer set callback

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback to set the value of a double mixer control that spans 2 registers.

Returns 0 for success.

int snd_soc_info_volsw_range(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_info * uinfo)

single mixer info callback with range.

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_info * uinfo
control element information

Description

Callback to provide information, within a range, about a single mixer control.

returns 0 for success.

int snd_soc_put_volsw_range(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

single mixer put value callback with range.

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback to set the value, within a range, for a single mixer control.

Returns 0 for success.

int snd_soc_get_volsw_range(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

single mixer get callback with range

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback to get the value, within a range, of a single mixer control.

Returns 0 for success.

int snd_soc_limit_volume(struct snd_soc_card * card, const char * name, int max)

Set new limit to an existing volume control.

Parameters

struct snd_soc_card * card
where to look for the control
const char * name
Name of the control
int max
new maximum limit

Description

Return 0 for success, else error.

int snd_soc_info_xr_sx(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_info * uinfo)

signed multi register info callback

Parameters

struct snd_kcontrol * kcontrol
mreg control
struct snd_ctl_elem_info * uinfo
control element information

Description

Callback to provide information of a control that can span multiple codec registers which together forms a single signed value in a MSB/LSB manner.

Returns 0 for success.

int snd_soc_get_xr_sx(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

signed multi register get callback

Parameters

struct snd_kcontrol * kcontrol
mreg control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback to get the value of a control that can span multiple codec registers which together forms a single signed value in a MSB/LSB manner. The control supports specifying total no of bits used to allow for bitfields across the multiple codec registers.

Returns 0 for success.

int snd_soc_put_xr_sx(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

signed multi register get callback

Parameters

struct snd_kcontrol * kcontrol
mreg control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback to set the value of a control that can span multiple codec registers which together forms a single signed value in a MSB/LSB manner. The control supports specifying total no of bits used to allow for bitfields across the multiple codec registers.

Returns 0 for success.

int snd_soc_get_strobe(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

strobe get callback

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback get the value of a strobe mixer control.

Returns 0 for success.

int snd_soc_put_strobe(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

strobe put callback

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback strobe a register bit to high then low (or the inverse) in one pass of a single mixer enum control.

Returns 1 for success.

int snd_soc_new_compress(struct snd_soc_pcm_runtime * rtd, int num)

create a new compress.

Parameters

struct snd_soc_pcm_runtime * rtd
The runtime for which we will create compress
int num
the device index number (zero based - shared with normal PCMs)

Return

0 for success, else error.

ASoC DAPM API

struct snd_soc_dapm_widget * snd_soc_dapm_kcontrol_widget(struct snd_kcontrol * kcontrol)

Returns the widget associated to a kcontrol

Parameters

struct snd_kcontrol * kcontrol
The kcontrol
struct snd_soc_dapm_context * snd_soc_dapm_kcontrol_dapm(struct snd_kcontrol * kcontrol)

Returns the dapm context associated to a kcontrol

Parameters

struct snd_kcontrol * kcontrol
The kcontrol

Note

This function must only be used on kcontrols that are known to have been registered for a CODEC. Otherwise the behaviour is undefined.

int snd_soc_dapm_force_bias_level(struct snd_soc_dapm_context * dapm, enum snd_soc_bias_level level)

Sets the DAPM bias level

Parameters

struct snd_soc_dapm_context * dapm
The DAPM context for which to set the level
enum snd_soc_bias_level level
The level to set

Description

Forces the DAPM bias level to a specific state. It will call the bias level callback of DAPM context with the specified level. This will even happen if the context is already at the same level. Furthermore it will not go through the normal bias level sequencing, meaning any intermediate states between the current and the target state will not be entered.

Note that the change in bias level is only temporary and the next time snd_soc_dapm_sync() is called the state will be set to the level as determined by the DAPM core. The function is mainly intended to be used to used during probe or resume from suspend to power up the device so initialization can be done, before the DAPM core takes over.

int snd_soc_dapm_sync_unlocked(struct snd_soc_dapm_context * dapm)

scan and power dapm paths

Parameters

struct snd_soc_dapm_context * dapm
DAPM context

Description

Walks all dapm audio paths and powers widgets according to their stream or path usage.

Requires external locking.

Returns 0 for success.

int snd_soc_dapm_sync(struct snd_soc_dapm_context * dapm)

scan and power dapm paths

Parameters

struct snd_soc_dapm_context * dapm
DAPM context

Description

Walks all dapm audio paths and powers widgets according to their stream or path usage.

Returns 0 for success.

int snd_soc_dapm_add_routes(struct snd_soc_dapm_context * dapm, const struct snd_soc_dapm_route * route, int num)

Add routes between DAPM widgets

Parameters

struct snd_soc_dapm_context * dapm
DAPM context
const struct snd_soc_dapm_route * route
audio routes
int num
number of routes

Description

Connects 2 dapm widgets together via a named audio path. The sink is the widget receiving the audio signal, whilst the source is the sender of the audio signal.

Returns 0 for success else error. On error all resources can be freed with a call to snd_soc_card_free().

int snd_soc_dapm_del_routes(struct snd_soc_dapm_context * dapm, const struct snd_soc_dapm_route * route, int num)

Remove routes between DAPM widgets

Parameters

struct snd_soc_dapm_context * dapm
DAPM context
const struct snd_soc_dapm_route * route
audio routes
int num
number of routes

Description

Removes routes from the DAPM context.

int snd_soc_dapm_weak_routes(struct snd_soc_dapm_context * dapm, const struct snd_soc_dapm_route * route, int num)

Mark routes between DAPM widgets as weak

Parameters

struct snd_soc_dapm_context * dapm
DAPM context
const struct snd_soc_dapm_route * route
audio routes
int num
number of routes

Description

Mark existing routes matching those specified in the passed array as being weak, meaning that they are ignored for the purpose of power decisions. The main intended use case is for sidetone paths which couple audio between other independent paths if they are both active in order to make the combination work better at the user level but which aren’t intended to be “used”.

Note that CODEC drivers should not use this as sidetone type paths can frequently also be used as bypass paths.

int snd_soc_dapm_new_widgets(struct snd_soc_card * card)

add new dapm widgets

Parameters

struct snd_soc_card * card
card to be checked for new dapm widgets

Description

Checks the codec for any new dapm widgets and creates them if found.

Returns 0 for success.

int snd_soc_dapm_get_volsw(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

dapm mixer get callback

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback to get the value of a dapm mixer control.

Returns 0 for success.

int snd_soc_dapm_put_volsw(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

dapm mixer set callback

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback to set the value of a dapm mixer control.

Returns 0 for success.

int snd_soc_dapm_get_enum_double(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

dapm enumerated double mixer get callback

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback to get the value of a dapm enumerated double mixer control.

Returns 0 for success.

int snd_soc_dapm_put_enum_double(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

dapm enumerated double mixer set callback

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
control element information

Description

Callback to set the value of a dapm enumerated double mixer control.

Returns 0 for success.

int snd_soc_dapm_info_pin_switch(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_info * uinfo)

Info for a pin switch

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_info * uinfo
control element information

Description

Callback to provide information about a pin switch control.

int snd_soc_dapm_get_pin_switch(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

Get information for a pin switch

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
Value
int snd_soc_dapm_put_pin_switch(struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol)

Set information for a pin switch

Parameters

struct snd_kcontrol * kcontrol
mixer control
struct snd_ctl_elem_value * ucontrol
Value
int snd_soc_dapm_new_controls(struct snd_soc_dapm_context * dapm, const struct snd_soc_dapm_widget * widget, int num)

create new dapm controls

Parameters

struct snd_soc_dapm_context * dapm
DAPM context
const struct snd_soc_dapm_widget * widget
widget array
int num
number of widgets

Description

Creates new DAPM controls based upon the templates.

Returns 0 for success else error.

int snd_soc_dapm_enable_pin_unlocked(struct snd_soc_dapm_context * dapm, const char * pin)

enable pin.

Parameters

struct snd_soc_dapm_context * dapm
DAPM context
const char * pin
pin name

Description

Enables input/output pin and its parents or children widgets iff there is a valid audio route and active audio stream.

Requires external locking.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_enable_pin(struct snd_soc_dapm_context * dapm, const char * pin)

enable pin.

Parameters

struct snd_soc_dapm_context * dapm
DAPM context
const char * pin
pin name

Description

Enables input/output pin and its parents or children widgets iff there is a valid audio route and active audio stream.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_force_enable_pin_unlocked(struct snd_soc_dapm_context * dapm, const char * pin)

force a pin to be enabled

Parameters

struct snd_soc_dapm_context * dapm
DAPM context
const char * pin
pin name

Description

Enables input/output pin regardless of any other state. This is intended for use with microphone bias supplies used in microphone jack detection.

Requires external locking.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_force_enable_pin(struct snd_soc_dapm_context * dapm, const char * pin)

force a pin to be enabled

Parameters

struct snd_soc_dapm_context * dapm
DAPM context
const char * pin
pin name

Description

Enables input/output pin regardless of any other state. This is intended for use with microphone bias supplies used in microphone jack detection.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_disable_pin_unlocked(struct snd_soc_dapm_context * dapm, const char * pin)

disable pin.

Parameters

struct snd_soc_dapm_context * dapm
DAPM context
const char * pin
pin name

Description

Disables input/output pin and its parents or children widgets.

Requires external locking.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_disable_pin(struct snd_soc_dapm_context * dapm, const char * pin)

disable pin.

Parameters

struct snd_soc_dapm_context * dapm
DAPM context
const char * pin
pin name

Description

Disables input/output pin and its parents or children widgets.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_nc_pin_unlocked(struct snd_soc_dapm_context * dapm, const char * pin)

permanently disable pin.

Parameters

struct snd_soc_dapm_context * dapm
DAPM context
const char * pin
pin name

Description

Marks the specified pin as being not connected, disabling it along any parent or child widgets. At present this is identical to snd_soc_dapm_disable_pin() but in future it will be extended to do additional things such as disabling controls which only affect paths through the pin.

Requires external locking.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_nc_pin(struct snd_soc_dapm_context * dapm, const char * pin)

permanently disable pin.

Parameters

struct snd_soc_dapm_context * dapm
DAPM context
const char * pin
pin name

Description

Marks the specified pin as being not connected, disabling it along any parent or child widgets. At present this is identical to snd_soc_dapm_disable_pin() but in future it will be extended to do additional things such as disabling controls which only affect paths through the pin.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_get_pin_status(struct snd_soc_dapm_context * dapm, const char * pin)

get audio pin status

Parameters

struct snd_soc_dapm_context * dapm
DAPM context
const char * pin
audio signal pin endpoint (or start point)

Description

Get audio pin status - connected or disconnected.

Returns 1 for connected otherwise 0.

int snd_soc_dapm_ignore_suspend(struct snd_soc_dapm_context * dapm, const char * pin)

ignore suspend status for DAPM endpoint

Parameters

struct snd_soc_dapm_context * dapm
DAPM context
const char * pin
audio signal pin endpoint (or start point)

Description

Mark the given endpoint or pin as ignoring suspend. When the system is disabled a path between two endpoints flagged as ignoring suspend will not be disabled. The path must already be enabled via normal means at suspend time, it will not be turned on if it was not already enabled.

void snd_soc_dapm_free(struct snd_soc_dapm_context * dapm)

free dapm resources

Parameters

struct snd_soc_dapm_context * dapm
DAPM context

Description

Free all dapm widgets and resources.

ASoC DMA Engine API

int snd_dmaengine_pcm_prepare_slave_config(struct snd_pcm_substream * substream, struct snd_pcm_hw_params * params, struct dma_slave_config * slave_config)

Generic prepare_slave_config callback

Parameters

struct snd_pcm_substream * substream
PCM substream
struct snd_pcm_hw_params * params
hw_params
struct dma_slave_config * slave_config
DMA slave config to prepare

Description

This function can be used as a generic prepare_slave_config callback for platforms which make use of the snd_dmaengine_dai_dma_data struct for their DAI DMA data. Internally the function will first call snd_hwparams_to_dma_slave_config to fill in the slave config based on the hw_params, followed by snd_dmaengine_set_config_from_dai_data to fill in the remaining fields based on the DAI DMA data.

int snd_dmaengine_pcm_register(struct device * dev, const struct snd_dmaengine_pcm_config * config, unsigned int flags)

Register a dmaengine based PCM device

Parameters

struct device * dev
The parent device for the PCM device
const struct snd_dmaengine_pcm_config * config
Platform specific PCM configuration
unsigned int flags
Platform specific quirks
void snd_dmaengine_pcm_unregister(struct device * dev)

Removes a dmaengine based PCM device

Parameters

struct device * dev
Parent device the PCM was register with

Description

Removes a dmaengine based PCM device previously registered with snd_dmaengine_pcm_register.

Miscellaneous Functions

Hardware-Dependent Devices API

int snd_hwdep_new(struct snd_card * card, char * id, int device, struct snd_hwdep ** rhwdep)

create a new hwdep instance

Parameters

struct snd_card * card
the card instance
char * id
the id string
int device
the device index (zero-based)
struct snd_hwdep ** rhwdep
the pointer to store the new hwdep instance

Description

Creates a new hwdep instance with the given index on the card. The callbacks (hwdep->ops) must be set on the returned instance after this call manually by the caller.

Return

Zero if successful, or a negative error code on failure.

Jack Abstraction Layer API

enum snd_jack_types

Jack types which can be reported

Constants

SND_JACK_HEADPHONE
Headphone
SND_JACK_MICROPHONE
Microphone
SND_JACK_HEADSET
Headset
SND_JACK_LINEOUT
Line out
SND_JACK_MECHANICAL
Mechanical switch
SND_JACK_VIDEOOUT
Video out
SND_JACK_AVOUT
AV (Audio Video) out
SND_JACK_LINEIN
Line in
SND_JACK_BTN_0
Button 0
SND_JACK_BTN_1
Button 1
SND_JACK_BTN_2
Button 2
SND_JACK_BTN_3
Button 3
SND_JACK_BTN_4
Button 4
SND_JACK_BTN_5
Button 5

Description

These values are used as a bitmask.

Note that this must be kept in sync with the lookup table in sound/core/jack.c.

int snd_jack_add_new_kctl(struct snd_jack * jack, const char * name, int mask)

Create a new snd_jack_kctl and add it to jack

Parameters

struct snd_jack * jack
the jack instance which the kctl will attaching to
const char * name
the name for the snd_kcontrol object
int mask
a bitmask of enum snd_jack_type values that can be detected by this snd_jack_kctl object.

Description

Creates a new snd_kcontrol object and adds it to the jack kctl_list.

Return

Zero if successful, or a negative error code on failure.

int snd_jack_new(struct snd_card * card, const char * id, int type, struct snd_jack ** jjack, bool initial_kctl, bool phantom_jack)

Create a new jack

Parameters

struct snd_card * card
the card instance
const char * id
an identifying string for this jack
int type
a bitmask of enum snd_jack_type values that can be detected by this jack
struct snd_jack ** jjack
Used to provide the allocated jack object to the caller.
bool initial_kctl
if true, create a kcontrol and add it to the jack list.
bool phantom_jack
Don’t create a input device for phantom jacks.

Description

Creates a new jack object.

Return

Zero if successful, or a negative error code on failure. On success jjack will be initialised.

void snd_jack_set_parent(struct snd_jack * jack, struct device * parent)

Set the parent device for a jack

Parameters

struct snd_jack * jack
The jack to configure
struct device * parent
The device to set as parent for the jack.

Description

Set the parent for the jack devices in the device tree. This function is only valid prior to registration of the jack. If no parent is configured then the parent device will be the sound card.

int snd_jack_set_key(struct snd_jack * jack, enum snd_jack_types type, int keytype)

Set a key mapping on a jack

Parameters

struct snd_jack * jack
The jack to configure
enum snd_jack_types type
Jack report type for this key
int keytype
Input layer key type to be reported

Description

Map a SND_JACK_BTN_ button type to an input layer key, allowing reporting of keys on accessories via the jack abstraction. If no mapping is provided but keys are enabled in the jack type then BTN_n numeric buttons will be reported.

If jacks are not reporting via the input API this call will have no effect.

Note that this is intended to be use by simple devices with small numbers of keys that can be reported. It is also possible to access the input device directly - devices with complex input capabilities on accessories should consider doing this rather than using this abstraction.

This function may only be called prior to registration of the jack.

Return

Zero if successful, or a negative error code on failure.

void snd_jack_report(struct snd_jack * jack, int status)

Report the current status of a jack

Parameters

struct snd_jack * jack
The jack to report status for
int status
The current status of the jack
int snd_soc_card_jack_new(struct snd_soc_card * card, const char * id, int type, struct snd_soc_jack * jack, struct snd_soc_jack_pin * pins, unsigned int num_pins)

Create a new jack

Parameters

struct snd_soc_card * card
ASoC card
const char * id
an identifying string for this jack
int type
a bitmask of enum snd_jack_type values that can be detected by this jack
struct snd_soc_jack * jack
structure to use for the jack
struct snd_soc_jack_pin * pins
Array of jack pins to be added to the jack or NULL
unsigned int num_pins
Number of elements in the pins array

Description

Creates a new jack object.

Returns zero if successful, or a negative error code on failure. On success jack will be initialised.

void snd_soc_jack_report(struct snd_soc_jack * jack, int status, int mask)

Report the current status for a jack

Parameters

struct snd_soc_jack * jack
the jack
int status
a bitmask of enum snd_jack_type values that are currently detected.
int mask
a bitmask of enum snd_jack_type values that being reported.

Description

If configured using snd_soc_jack_add_pins() then the associated DAPM pins will be enabled or disabled as appropriate and DAPM synchronised.

Note

This function uses mutexes and should be called from a context which can sleep (such as a workqueue).

int snd_soc_jack_add_zones(struct snd_soc_jack * jack, int count, struct snd_soc_jack_zone * zones)

Associate voltage zones with jack

Parameters

struct snd_soc_jack * jack
ASoC jack
int count
Number of zones
struct snd_soc_jack_zone * zones
Array of zones

Description

After this function has been called the zones specified in the array will be associated with the jack.

int snd_soc_jack_get_type(struct snd_soc_jack * jack, int micbias_voltage)

Based on the mic bias value, this function returns the type of jack from the zones declared in the jack type

Parameters

struct snd_soc_jack * jack
ASoC jack
int micbias_voltage
mic bias voltage at adc channel when jack is plugged in

Description

Based on the mic bias value passed, this function helps identify the type of jack from the already declared jack zones

int snd_soc_jack_add_pins(struct snd_soc_jack * jack, int count, struct snd_soc_jack_pin * pins)

Associate DAPM pins with an ASoC jack

Parameters

struct snd_soc_jack * jack
ASoC jack
int count
Number of pins
struct snd_soc_jack_pin * pins
Array of pins

Description

After this function has been called the DAPM pins specified in the pins array will have their status updated to reflect the current state of the jack whenever the jack status is updated.

void snd_soc_jack_notifier_register(struct snd_soc_jack * jack, struct notifier_block * nb)

Register a notifier for jack status

Parameters

struct snd_soc_jack * jack
ASoC jack
struct notifier_block * nb
Notifier block to register

Description

Register for notification of the current status of the jack. Note that it is not possible to report additional jack events in the callback from the notifier, this is intended to support applications such as enabling electrical detection only when a mechanical detection event has occurred.

void snd_soc_jack_notifier_unregister(struct snd_soc_jack * jack, struct notifier_block * nb)

Unregister a notifier for jack status

Parameters

struct snd_soc_jack * jack
ASoC jack
struct notifier_block * nb
Notifier block to unregister

Description

Stop notifying for status changes.

int snd_soc_jack_add_gpios(struct snd_soc_jack * jack, int count, struct snd_soc_jack_gpio * gpios)

Associate GPIO pins with an ASoC jack

Parameters

struct snd_soc_jack * jack
ASoC jack
int count
number of pins
struct snd_soc_jack_gpio * gpios
array of gpio pins

Description

This function will request gpio, set data direction and request irq for each gpio in the array.

int snd_soc_jack_add_gpiods(struct device * gpiod_dev, struct snd_soc_jack * jack, int count, struct snd_soc_jack_gpio * gpios)

Associate GPIO descriptor pins with an ASoC jack

Parameters

struct device * gpiod_dev
GPIO consumer device
struct snd_soc_jack * jack
ASoC jack
int count
number of pins
struct snd_soc_jack_gpio * gpios
array of gpio pins

Description

This function will request gpio, set data direction and request irq for each gpio in the array.

void snd_soc_jack_free_gpios(struct snd_soc_jack * jack, int count, struct snd_soc_jack_gpio * gpios)

Release GPIO pins’ resources of an ASoC jack

Parameters

struct snd_soc_jack * jack
ASoC jack
int count
number of pins
struct snd_soc_jack_gpio * gpios
array of gpio pins

Description

Release gpio and irq resources for gpio pins associated with an ASoC jack.

ISA DMA Helpers

void snd_dma_program(unsigned long dma, unsigned long addr, unsigned int size, unsigned short mode)

program an ISA DMA transfer

Parameters

unsigned long dma
the dma number
unsigned long addr
the physical address of the buffer
unsigned int size
the DMA transfer size
unsigned short mode
the DMA transfer mode, DMA_MODE_XXX

Description

Programs an ISA DMA transfer for the given buffer.

void snd_dma_disable(unsigned long dma)

stop the ISA DMA transfer

Parameters

unsigned long dma
the dma number

Description

Stops the ISA DMA transfer.

unsigned int snd_dma_pointer(unsigned long dma, unsigned int size)

return the current pointer to DMA transfer buffer in bytes

Parameters

unsigned long dma
the dma number
unsigned int size
the dma transfer size

Return

The current pointer in DMA transfer buffer in bytes.

Other Helper Macros

snd_printk(fmt, args...)

printk wrapper

Parameters

fmt
format string
args...
variable arguments

Description

Works like printk() but prints the file and the line of the caller when configured with CONFIG_SND_VERBOSE_PRINTK.

snd_printd(fmt, args...)

debug printk

Parameters

fmt
format string
args...
variable arguments

Description

Works like snd_printk() for debugging purposes. Ignored when CONFIG_SND_DEBUG is not set.

snd_BUG()

give a BUG warning message and stack trace

Parameters

Description

Calls WARN() if CONFIG_SND_DEBUG is set. Ignored when CONFIG_SND_DEBUG is not set.

snd_printd_ratelimit()

Parameters

snd_BUG_ON(cond)

debugging check macro

Parameters

cond
condition to evaluate

Description

Has the same behavior as WARN_ON when CONFIG_SND_DEBUG is set, otherwise just evaluates the conditional and returns the value.

snd_printdd(format, args...)

debug printk

Parameters

format
format string
args...
variable arguments

Description

Works like snd_printk() for debugging purposes. Ignored when CONFIG_SND_DEBUG_VERBOSE is not set.