Sound Devices

voidsnd_card_unref(struct snd_card * card)

Unreference the card object

Parameters

structsnd_card*card
the card object to unreference

Description

Call this function for the card object that was obtained viasnd_card_ref()orsnd_lookup_minor_data().

snd_printk(fmt,…)

printk wrapper

Parameters

fmt
format string
...
variable arguments

Description

Works likeprintk() but prints the file and the line of the callerwhen configured with CONFIG_SND_VERBOSE_PRINTK.

snd_printd(fmt,…)

debug printk

Parameters

fmt
format string
...
variable arguments

Description

Works likesnd_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,…)

debug printk

Parameters

format
format string
...
variable arguments

Description

Works likesnd_printk() for debugging purposes.Ignored when CONFIG_SND_DEBUG_VERBOSE is not set.

intregister_sound_special_device(const struct file_operations * fops, int unit, structdevice * dev)

register a special sound node

Parameters

conststructfile_operations*fops
File operations for the driver
intunit
Unit number to allocate
structdevice*dev

device pointer

Allocate a special sound device by minor number from the soundsubsystem.

Return

The allocated number is returned on success. On failure,
a negative error code is returned.
intregister_sound_mixer(const struct file_operations * fops, int dev)

register a mixer device

Parameters

conststructfile_operations*fops
File operations for the driver
intdev

Unit number to allocate

Allocate a mixer device. Unit is the number of the mixer requested.Pass -1 to request the next free mixer unit.

Return

On success, the allocated number is returned. On failure,
a negative error code is returned.
intregister_sound_dsp(const struct file_operations * fops, int dev)

register a DSP device

Parameters

conststructfile_operations*fops
File operations for the driver
intdev

Unit number to allocate

Allocate a DSP device. Unit is the number of the DSP requested.Pass -1 to request the next free DSP unit.

This function allocates both the audio and dsp device entries togetherand will always allocate them as a matching pair - eg dsp3/audio3

Return

On success, the allocated number is returned. On failure,
a negative error code is returned.
voidunregister_sound_special(int unit)

unregister a special sound device

Parameters

intunit

unit number to allocate

Release a sound device that was allocated withregister_sound_special(). The unit passed is the return value fromthe register function.

voidunregister_sound_mixer(int unit)

unregister a mixer

Parameters

intunit

unit number to allocate

Release a sound device that was allocated withregister_sound_mixer().The unit passed is the return value from the register function.

voidunregister_sound_dsp(int unit)

unregister a DSP device

Parameters

intunit

unit number to allocate

Release a sound device that was allocated withregister_sound_dsp().The unit passed is the return value from the register function.

Both of the allocated units are released together automatically.

intsnd_pcm_stream_linked(struct snd_pcm_substream * substream)

Check whether the substream is linked with others

Parameters

structsnd_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 likesnd_pcm_stream_lock() but with the localIRQ (only when nonatomic is false). In nonatomic case, this is identicalassnd_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 givensubstream.Whensubstream isn’t linked with any others, this gives returnssubstreamitself once.

intsnd_pcm_running(struct snd_pcm_substream * substream)

Check whether the substream is in a running state

Parameters

structsnd_pcm_substream*substream
substream to check

Description

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

ssize_tbytes_to_samples(struct snd_pcm_runtime * runtime, ssize_t size)

Unit conversion of the size from bytes to samples

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance
ssize_tsize
size in bytes
snd_pcm_sframes_tbytes_to_frames(struct snd_pcm_runtime * runtime, ssize_t size)

Unit conversion of the size from bytes to frames

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance
ssize_tsize
size in bytes
ssize_tsamples_to_bytes(struct snd_pcm_runtime * runtime, ssize_t size)

Unit conversion of the size from samples to bytes

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance
ssize_tsize
size in samples
ssize_tframes_to_bytes(struct snd_pcm_runtime * runtime, snd_pcm_sframes_t size)

Unit conversion of the size from frames to bytes

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance
snd_pcm_sframes_tsize
size in frames
intframe_aligned(struct snd_pcm_runtime * runtime, ssize_t bytes)

Check whether the byte size is aligned to frames

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance
ssize_tbytes
size in bytes
size_tsnd_pcm_lib_buffer_bytes(struct snd_pcm_substream * substream)

Get the buffer size of the current PCM in bytes

Parameters

structsnd_pcm_substream*substream
PCM substream
size_tsnd_pcm_lib_period_bytes(struct snd_pcm_substream * substream)

Get the period size of the current PCM in bytes

Parameters

structsnd_pcm_substream*substream
PCM substream
snd_pcm_uframes_tsnd_pcm_playback_avail(struct snd_pcm_runtime * runtime)

Get the available (writable) space for playback

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance

Description

Result is between 0 … (boundary - 1)

snd_pcm_uframes_tsnd_pcm_capture_avail(struct snd_pcm_runtime * runtime)

Get the available (readable) space for capture

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance

Description

Result is between 0 … (boundary - 1)

snd_pcm_sframes_tsnd_pcm_playback_hw_avail(struct snd_pcm_runtime * runtime)

Get the queued space for playback

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance
snd_pcm_sframes_tsnd_pcm_capture_hw_avail(struct snd_pcm_runtime * runtime)

Get the free space for capture

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance
intsnd_pcm_playback_ready(struct snd_pcm_substream * substream)

check whether the playback buffer is available

Parameters

structsnd_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.

intsnd_pcm_capture_ready(struct snd_pcm_substream * substream)

check whether the capture buffer is available

Parameters

structsnd_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.

intsnd_pcm_playback_data(struct snd_pcm_substream * substream)

check whether any data exists on the playback buffer

Parameters

structsnd_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_thresholdis bigger or equal to boundary, then this function returns always non-zero.

intsnd_pcm_playback_empty(struct snd_pcm_substream * substream)

check whether the playback buffer is empty

Parameters

structsnd_pcm_substream*substream
the pcm substream instance

Description

Checks whether the playback buffer is empty.

Return

Non-zero if empty, or zero if not.

intsnd_pcm_capture_empty(struct snd_pcm_substream * substream)

check whether the capture buffer is empty

Parameters

structsnd_pcm_substream*substream
the pcm substream instance

Description

Checks whether the capture buffer is empty.

Return

Non-zero if empty, or zero if not.

voidsnd_pcm_trigger_done(struct snd_pcm_substream * substream, struct snd_pcm_substream * master)

Mark the master substream

Parameters

structsnd_pcm_substream*substream
the pcm substream instance
structsnd_pcm_substream*master
the linked master substream

Description

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

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

unsigned intparams_channels(const struct snd_pcm_hw_params * p)

Get the number of channels from the hw params

Parameters

conststructsnd_pcm_hw_params*p
hw params
unsigned intparams_rate(const struct snd_pcm_hw_params * p)

Get the sample rate from the hw params

Parameters

conststructsnd_pcm_hw_params*p
hw params
unsigned intparams_period_size(const struct snd_pcm_hw_params * p)

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

Parameters

conststructsnd_pcm_hw_params*p
hw params
unsigned intparams_periods(const struct snd_pcm_hw_params * p)

Get the number of periods from the hw params

Parameters

conststructsnd_pcm_hw_params*p
hw params
unsigned intparams_buffer_size(const struct snd_pcm_hw_params * p)

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

Parameters

conststructsnd_pcm_hw_params*p
hw params
unsigned intparams_buffer_bytes(const struct snd_pcm_hw_params * p)

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

Parameters

conststructsnd_pcm_hw_params*p
hw params
intsnd_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

structsnd_pcm_runtime*runtime
PCM runtime instance
snd_pcm_hw_param_tvar
The hw_params variable to constrain
unsignedintval
The value to constrain to

Return

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

intsnd_pcm_format_cpu_endian(snd_pcm_format_t format)

Check the PCM format is CPU-endian

Parameters

snd_pcm_format_tformat
the format to check

Return

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

voidsnd_pcm_set_runtime_buffer(struct snd_pcm_substream * substream, struct snd_dma_buffer * bufp)

Set the PCM runtime buffer

Parameters

structsnd_pcm_substream*substream
PCM substream to set
structsnd_dma_buffer*bufp
the buffer information, NULL to clear

Description

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

voidsnd_pcm_gettime(struct snd_pcm_runtime * runtime, struct timespec64 * tv)

Fill the timespec64 depending on the timestamp mode

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance
structtimespec64*tv
timespec64 to fill
intsnd_pcm_lib_alloc_vmalloc_buffer(struct snd_pcm_substream * substream, size_t size)

allocate virtual DMA buffer

Parameters

structsnd_pcm_substream*substream
the substream to allocate the buffer to
size_tsize
the requested buffer size, in bytes

Description

Allocates the PCM substream buffer usingvmalloc(), i.e., the memory iscontiguous in kernel virtual space, but not in physical memory. Use thisif 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 errorcode.

intsnd_pcm_lib_alloc_vmalloc_32_buffer(struct snd_pcm_substream * substream, size_t size)

allocate 32-bit-addressable buffer

Parameters

structsnd_pcm_substream*substream
the substream to allocate the buffer to
size_tsize
the requested buffer size, in bytes

Description

This function works likesnd_pcm_lib_alloc_vmalloc_buffer(), but usesvmalloc_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 errorcode.

dma_addr_tsnd_pcm_sgbuf_get_addr(struct snd_pcm_substream * substream, unsigned int ofs)

Get the DMA address at the corresponding offset

Parameters

structsnd_pcm_substream*substream
PCM substream
unsignedintofs
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

structsnd_pcm_substream*substream
PCM substream
unsignedintofs
byte offset
unsigned intsnd_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

structsnd_pcm_substream*substream
PCM substream
unsignedintofs
byte offset
unsignedintsize
byte size to examine
voidsnd_pcm_mmap_data_open(struct vm_area_struct * area)

increase the mmap counter

Parameters

structvm_area_struct*area
VMA

Description

PCM mmap callback should handle this counter properly

voidsnd_pcm_mmap_data_close(struct vm_area_struct * area)

decrease the mmap counter

Parameters

structvm_area_struct*area
VMA

Description

PCM mmap callback should handle this counter properly

voidsnd_pcm_limit_isa_dma_size(int dma, size_t * max)

Get the max size fitting with ISA DMA transfer

Parameters

intdma
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

structsnd_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

structsnd_pcm_chmap*info
chmap information
unsignedintidx
the substream number index
u64pcm_format_to_bits(snd_pcm_format_t pcm_format)

Strong-typed conversion of pcm_format to bitwise

Parameters

snd_pcm_format_tpcm_format
PCM format
pcm_for_each_format(f)

helper to iterate for each format type

Parameters

f
the iterator variable in snd_pcm_format_t type
const char *snd_pcm_format_name(snd_pcm_format_t format)

Return a name string for the given PCM format

Parameters

snd_pcm_format_tformat
PCM format
intsnd_pcm_new_stream(struct snd_pcm * pcm, int stream, int substream_count)

create a new PCM stream

Parameters

structsnd_pcm*pcm
the pcm instance
intstream
the stream direction, SNDRV_PCM_STREAM_XXX
intsubstream_count
the number of substreams

Description

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

Return

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

intsnd_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

structsnd_card*card
the card instance
constchar*id
the id string
intdevice
the device index (zero based)
intplayback_count
the number of substreams for playback
intcapture_count
the number of substreams for capture
structsnd_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 instanceviasnd_pcm_set_ops().

Return

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

intsnd_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

structsnd_card*card
the card instance
constchar*id
the id string
intdevice
the device index (zero based - shared with normal PCMs)
intplayback_count
the number of substreams for playback
intcapture_count
the number of substreams for capture
structsnd_pcm**rpcm
the pointer to store the new pcm instance

Description

Creates a new internal PCM instance with no userspace device or procfsentries. This is used by ASoC Back End PCMs in order to create a PCM thatwill only be used internally by kernel drivers. i.e. it cannot be openedby userspace. It provides existing ASoC components drivers with a substreamand access to any private data.

The pcm operators have to be set afterwards to the new instanceviasnd_pcm_set_ops().

Return

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

intsnd_pcm_notify(structsnd_pcm_notify * notify, int nfree)

Add/remove the notify list

Parameters

structsnd_pcm_notify*notify
PCM notify list
intnfree
0 = register, 1 = unregister

Description

This adds the given notifier to the global list so that the callback iscalled for each registered PCM devices. This exists only for PCM OSSemulation, so far.

intsnd_device_new(struct snd_card * card, enum snd_device_type type, void * device_data, const struct snd_device_ops * ops)

create an ALSA device component

Parameters

structsnd_card*card
the card instance
enumsnd_device_typetype
the device type, SNDRV_DEV_XXX
void*device_data
the data pointer of this device
conststructsnd_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 togetherby the card.

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

Return

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

voidsnd_device_disconnect(struct snd_card * card, void * device_data)

disconnect the device

Parameters

structsnd_card*card
the card instance
void*device_data
the data pointer to disconnect

Description

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

Usually called fromsnd_card_disconnect().

Return

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

voidsnd_device_free(struct snd_card * card, void * device_data)

release the device from the card

Parameters

structsnd_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 thecallbacks, dev_disconnect and dev_free, corresponding to the state.Then release the device.

intsnd_device_register(struct snd_card * card, void * device_data)

register the device

Parameters

structsnd_card*card
the card instance
void*device_data
the data pointer to register

Description

Registers the device which was already created viasnd_device_new(). Usually this is called fromsnd_card_register(),but it can be called later if any new devices are created afterinvocation ofsnd_card_register().

Return

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

intsnd_device_get_state(struct snd_card * card, void * device_data)

Get the current state of the given device

Parameters

structsnd_card*card
the card instance
void*device_data
the data pointer to release

Description

Returns the current state of the given device object. For the validdevice, eitherSNDRV_DEV_BUILD,SNDRV_DEV_REGISTERED orSNDRV_DEV_DISCONNECTED is returned.Or for a non-existing device, -1 is returned as an error.

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

read one line from the procfs buffer

Parameters

structsnd_info_buffer*buffer
the procfs buffer
char*line
the buffer to store
intlen
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
constchar*src
the original string
intlen
the max. length of token - 1

Description

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

Return

The updated pointer of the original string so thatit 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

structmodule*module
the module pointer
constchar*name
the file name
structsnd_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, orNULL 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

structsnd_card*card
the card instance
constchar*name
the file name
structsnd_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, orNULL on failure.

voidsnd_info_free_entry(struct snd_info_entry * entry)

release the info entry

Parameters

structsnd_info_entry*entry
the info entry

Description

Releases the info entry.

intsnd_info_register(struct snd_info_entry * entry)

register the info entry

Parameters

structsnd_info_entry*entry
the info entry

Description

Registers the proc info entry.The all children entries are registered recursively.

Return

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

intsnd_card_rw_proc_new(struct snd_card * card, const char * name, void * private_data, void (*read)(struct snd_info_entry *, struct snd_info_buffer *), void (*write) (struct snd_info_entry *entry, struct snd_info_buffer *buffer))

Create a read/write text proc file entry for the card

Parameters

structsnd_card*card
the card instance
constchar*name
the file name
void*private_data
the arbitrary private data
void(*)(structsnd_info_entry*,structsnd_info_buffer*)read
the read callback
void(*)(structsnd_info_entry*entry,structsnd_info_buffer*buffer)write
the write callback, NULL for read-only

Description

This proc file entry will be registered viasnd_card_register() call, andit will be removed automatically at the card removal, too.

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

receive the input data from the device

Parameters

structsnd_rawmidi_substream*substream
the rawmidi substream
constunsignedchar*buffer
the buffer pointer
intcount
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.

intsnd_rawmidi_transmit_empty(struct snd_rawmidi_substream * substream)

check whether the output buffer is empty

Parameters

structsnd_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

structsnd_rawmidi_substream*substream
the rawmidi substream
unsignedchar*buffer
the buffer pointer
intcount
data size to transfer

Description

This is a variant ofsnd_rawmidi_transmit_peek() without spinlock.

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

copy data from the internal buffer

Parameters

structsnd_rawmidi_substream*substream
the rawmidi substream
unsignedchar*buffer
the buffer pointer
intcount
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 callsnd_rawmidi_transmit_ack() after the transmission isfinished.

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

structsnd_rawmidi_substream*substream
the rawmidi substream
intcount
the transferred count

Description

This is a variant of__snd_rawmidi_transmit_ack() without spinlock.

intsnd_rawmidi_transmit_ack(struct snd_rawmidi_substream * substream, int count)

acknowledge the transmission

Parameters

structsnd_rawmidi_substream*substream
the rawmidi substream
intcount
the transferred count

Description

Advances the hardware pointer for the internal output buffer withthe 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.

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

copy from the buffer to the device

Parameters

structsnd_rawmidi_substream*substream
the rawmidi substream
unsignedchar*buffer
the buffer pointer
intcount
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.

intsnd_rawmidi_proceed(struct snd_rawmidi_substream * substream)

Discard the all pending bytes and proceed

Parameters

structsnd_rawmidi_substream*substream
rawmidi substream

Return

the number of discarded bytes

intsnd_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

structsnd_card*card
the card instance
char*id
the id string
intdevice
the device index
intoutput_count
the number of output streams
intinput_count
the number of input streams
structsnd_rawmidi**rrawmidi
the pointer to store the new rawmidi instance

Description

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

Return

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

voidsnd_rawmidi_set_ops(struct snd_rawmidi * rmidi, int stream, const struct snd_rawmidi_ops * ops)

set the rawmidi operators

Parameters

structsnd_rawmidi*rmidi
the rawmidi instance
intstream
the stream direction, SNDRV_RAWMIDI_STREAM_XXX
conststructsnd_rawmidi_ops*ops
the operator table

Description

Sets the rawmidi operators for the given stream direction.

voidsnd_request_card(int card)

try to load the card module

Parameters

intcard
the card number

Description

Tries to load the module “snd-card-X” for the given card numbervia 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

unsignedintminor
the minor number
inttype
device type (SNDRV_DEVICE_TYPE_XXX)

Description

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

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

Return

The user data pointer if the specified device is found.NULLotherwise.

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

Register the ALSA device file for the card

Parameters

inttype
the device type, SNDRV_DEVICE_TYPE_XXX
structsnd_card*card
the card instance
intdev
the device index
conststructfile_operations*f_ops
the file operations
void*private_data
user pointer for f_ops->open()
structdevice*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.

intsnd_unregister_device(structdevice * dev)

unregister the device on the given card

Parameters

structdevice*dev
the device instance

Description

Unregisters the device file already registered viasnd_register_device().

Return

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

intcopy_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
constvolatilevoid__iomem*src
the source pointer on mmio
size_tcount
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.

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

copy data from user-space to mmio-space

Parameters

volatilevoid__iomem*dst
the destination pointer on mmio-space
constvoid__user*src
the source pointer on user-space
size_tcount
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.

voidsnd_pcm_lib_preallocate_free_for_all(struct snd_pcm * pcm)

release all pre-allocated buffers on the pcm

Parameters

structsnd_pcm*pcm
the pcm instance

Description

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

voidsnd_pcm_lib_preallocate_pages(struct snd_pcm_substream * substream, int type, structdevice * data, size_t size, size_t max)

pre-allocation for the given DMA type

Parameters

structsnd_pcm_substream*substream
the pcm substream instance
inttype
DMA type (SNDRV_DMA_TYPE_*)
structdevice*data
DMA type dependent data
size_tsize
the requested pre-allocation size in bytes
size_tmax
the max. allowed pre-allocation size

Description

Do pre-allocation for the given DMA buffer type.

voidsnd_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

structsnd_pcm*pcm
the pcm instance
inttype
DMA type (SNDRV_DMA_TYPE_*)
void*data
DMA type dependent data
size_tsize
the requested pre-allocation size in bytes
size_tmax
the max. allowed pre-allocation size

Description

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

voidsnd_pcm_set_managed_buffer(struct snd_pcm_substream * substream, int type, structdevice * data, size_t size, size_t max)

set up buffer management for a substream

Parameters

structsnd_pcm_substream*substream
the pcm substream instance
inttype
DMA type (SNDRV_DMA_TYPE_*)
structdevice*data
DMA type dependent data
size_tsize
the requested pre-allocation size in bytes
size_tmax
the max. allowed pre-allocation size

Description

Do pre-allocation for the given DMA buffer type, and set the managedbuffer allocation mode to the given substream.In this mode, PCM core will allocate a buffer automatically before PCMhw_params ops call, and release the buffer after PCM hw_free ops callas well, so that the driver doesn’t need to invoke the allocation andthe release explicitly in its callback.When a buffer is actually allocated before the PCM hw_params call, itturns on the runtime buffer_changed flag for drivers changing their h/wparameters accordingly.

voidsnd_pcm_set_managed_buffer_all(struct snd_pcm * pcm, int type, structdevice * data, size_t size, size_t max)

set up buffer management for all substreams for all substreams

Parameters

structsnd_pcm*pcm
the pcm instance
inttype
DMA type (SNDRV_DMA_TYPE_*)
structdevice*data
DMA type dependent data
size_tsize
the requested pre-allocation size in bytes
size_tmax
the max. allowed pre-allocation size

Description

Do pre-allocation to all substreams of the given pcm for the specified DMAtype and size, and set the managed_buffer_alloc flag to each substream.

intsnd_pcm_lib_malloc_pages(struct snd_pcm_substream * substream, size_t size)

allocate the DMA buffer

Parameters

structsnd_pcm_substream*substream
the substream to allocate the DMA buffer to
size_tsize
the requested buffer size in bytes

Description

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

Return

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

intsnd_pcm_lib_free_pages(struct snd_pcm_substream * substream)

release the allocated DMA buffer.

Parameters

structsnd_pcm_substream*substream
the substream to release the DMA buffer

Description

Releases the DMA buffer allocated viasnd_pcm_lib_malloc_pages().

Return

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

intsnd_pcm_lib_free_vmalloc_buffer(struct snd_pcm_substream * substream)

free vmalloc buffer

Parameters

structsnd_pcm_substream*substream
the substream with a buffer allocated bysnd_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

structsnd_pcm_substream*substream
the substream with a buffer allocated bysnd_pcm_lib_alloc_vmalloc_buffer()
unsignedlongoffset
offset in the buffer

Description

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

Return

The page struct, orNULL on failure.

voidsnd_device_initialize(structdevice * dev, struct snd_card * card)

Initialize struct device for sound devices

Parameters

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

create and initialize a soundcard structure

Parameters

structdevice*parent
the parent device object
intidx
card index (address) [0 … (SNDRV_CARDS-1)]
constchar*xid
card identification (ASCII string)
structmodule*module
top level module for locking
intextra_size
allocate this extra size after the main soundcard structure
structsnd_card**card_ret

the pointer to store the created card instance

Creates and initializes a soundcard structure.

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

Return

Zero if successful or a negative error code.

struct snd_card *snd_card_ref(int idx)

Get the card object from the index

Parameters

intidx
the card index

Description

Returns a card object corresponding to the given index or NULL if not found.Release the object viasnd_card_unref().

intsnd_card_disconnect(struct snd_card * card)

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

Parameters

structsnd_card*card

soundcard structure

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).
voidsnd_card_disconnect_sync(struct snd_card * card)

disconnect card and wait until files get closed

Parameters

structsnd_card*card
card object to disconnect

Description

This callssnd_card_disconnect() for disconnecting all belonging componentsand waits until all pending files get closed.It assures that all accesses from user-space finished so that the drivercan release its resources gracefully.

intsnd_card_free_when_closed(struct snd_card * card)

Disconnect the card, free it later eventually

Parameters

structsnd_card*card
soundcard structure

Description

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

intsnd_card_free(struct snd_card * card)

frees given soundcard structure

Parameters

structsnd_card*card
soundcard structure

Description

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

This function waits until the all resources are properly released.

Return

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

voidsnd_card_set_id(struct snd_card * card, const char * nid)

set card identification name

Parameters

structsnd_card*card
soundcard structure
constchar*nid

new identification string

This function sets the card identification and checks for namecollisions.

intsnd_card_add_dev_attr(struct snd_card * card, const struct attribute_group * group)

Append a new sysfs attribute group to card

Parameters

structsnd_card*card
card instance
conststructattribute_group*group
attribute group to append
intsnd_card_register(struct snd_card * card)

register the soundcard

Parameters

structsnd_card*card

soundcard structure

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

Return

Zero otherwise a negative error code if the registration failed.

intsnd_component_add(struct snd_card * card, const char * component)

add a component string

Parameters

structsnd_card*card
soundcard structure
constchar*component

the component id string

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.

intsnd_card_file_add(struct snd_card * card, struct file * file)

add the file to the file list of the card

Parameters

structsnd_card*card
soundcard structure
structfile*file

file pointer

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.

intsnd_card_file_remove(struct snd_card * card, struct file * file)

remove the file from the file list

Parameters

structsnd_card*card
soundcard structure
structfile*file

file pointer

This function removes the file formerly added to the card viasnd_card_file_add() function.If all files are removed andsnd_card_free_when_closed() wascalled beforehand, it processes the pending release ofresources.

Return

Zero or a negative error code.

intsnd_power_wait(struct snd_card * card, unsigned int power_state)

wait until the power-state is changed.

Parameters

structsnd_card*card
soundcard structure
unsignedintpower_state

expected power state

Waits until the power-state is changed.

Return

Zero if successful, or a negative error code.

voidsnd_dma_program(unsigned long dma, unsigned long addr, unsigned int size, unsigned short mode)

program an ISA DMA transfer

Parameters

unsignedlongdma
the dma number
unsignedlongaddr
the physical address of the buffer
unsignedintsize
the DMA transfer size
unsignedshortmode
the DMA transfer mode, DMA_MODE_XXX

Description

Programs an ISA DMA transfer for the given buffer.

voidsnd_dma_disable(unsigned long dma)

stop the ISA DMA transfer

Parameters

unsignedlongdma
the dma number

Description

Stops the ISA DMA transfer.

unsigned intsnd_dma_pointer(unsigned long dma, unsigned int size)

return the current pointer to DMA transfer buffer in bytes

Parameters

unsignedlongdma
the dma number
unsignedintsize
the dma transfer size

Return

The current pointer in DMA transfer buffer in bytes.

voidsnd_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

structsnd_card*card
the card to send notification
unsignedintmask
the event mask, SNDRV_CTL_EVENT_*
structsnd_ctl_elem_id*id
the ctl element id to send notification

Description

This function adds an event record with the given id and mask, appendsto the list and wakes up the user-space for notification. This can becalled 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

conststructsnd_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 giventemplate. When the access field of ncontrol is 0, it’s assumed asREADWRITE access. When the count field is 0, it’s assumes as one.

Return

The pointer of the newly generated instance, orNULL on failure.

voidsnd_ctl_free_one(struct snd_kcontrol * kcontrol)

release the control instance

Parameters

structsnd_kcontrol*kcontrol
the control instance

Description

Releases the control instance created viasnd_ctl_new()orsnd_ctl_new1().Don’t call this after the control was added to the card.

intsnd_ctl_add(struct snd_card * card, struct snd_kcontrol * kcontrol)

add the control instance to the card

Parameters

structsnd_card*card
the card instance
structsnd_kcontrol*kcontrol
the control instance to add

Description

Adds the control instance created viasnd_ctl_new() orsnd_ctl_new1() to the given card. Assigns also an uniquenumid used for fast search.

It frees automatically the control which cannot be added.

Return

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

intsnd_ctl_replace(struct snd_card * card, struct snd_kcontrol * kcontrol, bool add_on_replace)

replace the control instance of the card

Parameters

structsnd_card*card
the card instance
structsnd_kcontrol*kcontrol
the control instance to replace
booladd_on_replace
add the control if not already added

Description

Replaces the given control. If the given control does not existand the add_on_replace flag is set, the control is added. If thecontrol 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.

intsnd_ctl_remove(struct snd_card * card, struct snd_kcontrol * kcontrol)

remove the control from the card and release it

Parameters

structsnd_card*card
the card instance
structsnd_kcontrol*kcontrol
the control instance to remove

Description

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

Return

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

intsnd_ctl_remove_id(struct snd_card * card, struct snd_ctl_elem_id * id)

remove the control of the given id and release it

Parameters

structsnd_card*card
the card instance
structsnd_ctl_elem_id*id
the control id to remove

Description

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

Return

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

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

activate/inactivate the control of the given id

Parameters

structsnd_card*card
the card instance
structsnd_ctl_elem_id*id
the control id to activate/inactivate
intactive
non-zero to activate

Description

Finds the control instance with the given id, and activate orinactivate 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.

intsnd_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

structsnd_card*card
the card instance
structsnd_ctl_elem_id*src_id
the old id
structsnd_ctl_elem_id*dst_id
the new id

Description

Finds the control with the old id from the card, and replaces theid 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

structsnd_card*card
the card instance
unsignedintnumid
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, orNULL 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

structsnd_card*card
the card instance
structsnd_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, orNULL if not.

intsnd_ctl_register_ioctl(snd_kctl_ioctl_func_t fcn)

register the device-specific control-ioctls

Parameters

snd_kctl_ioctl_func_tfcn
ioctl callback function

Description

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

intsnd_ctl_register_ioctl_compat(snd_kctl_ioctl_func_t fcn)

register the device-specific 32bit compat control-ioctls

Parameters

snd_kctl_ioctl_func_tfcn
ioctl callback function
intsnd_ctl_unregister_ioctl(snd_kctl_ioctl_func_t fcn)

de-register the device-specific control-ioctls

Parameters

snd_kctl_ioctl_func_tfcn
ioctl callback function to unregister
intsnd_ctl_unregister_ioctl_compat(snd_kctl_ioctl_func_t fcn)

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

Parameters

snd_kctl_ioctl_func_tfcn
ioctl callback function to unregister
intsnd_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

structsnd_kcontrol*kcontrol
the kcontrol instance
structsnd_ctl_elem_info*uinfo
info to store

Description

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

intsnd_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

structsnd_kcontrol*kcontrol
the kcontrol instance
structsnd_ctl_elem_info*uinfo
info to store

Description

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

intsnd_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

structsnd_ctl_elem_info*info
the structure to be filled
unsignedintchannels
the number of the control’s channels; often one
unsignedintitems
the number of control values; also the size ofnames
constchar*constnames
an array containing the names of all control values

Description

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

Return

Zero.

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

set the PCM operators

Parameters

structsnd_pcm*pcm
the pcm instance
intdirection
stream direction, SNDRV_PCM_STREAM_XXX
conststructsnd_pcm_ops*ops
the operator table

Description

Sets the given PCM operators to the pcm instance.

voidsnd_pcm_set_sync(struct snd_pcm_substream * substream)

set the PCM sync id

Parameters

structsnd_pcm_substream*substream
the pcm substream

Description

Sets the PCM sync identifier for the card.

intsnd_interval_refine(struct snd_interval * i, const struct snd_interval * v)

refine the interval value of configurator

Parameters

structsnd_interval*i
the interval value to refine
conststructsnd_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 anegative error code.

intsnd_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

structsnd_interval*i
interval to refine
unsignedintrats_count
number of ratnum_t
conststructsnd_ratnum*rats
ratnum_t array
unsignedint*nump
pointer to store the resultant numerator
unsignedint*denp
pointer to store the resultant denominator

Return

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

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

refine the interval value from the list

Parameters

structsnd_interval*i
the interval value to refine
unsignedintcount
the number of elements in the list
constunsignedint*list
the value list
unsignedintmask
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 areevaluated.

Return

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

intsnd_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

structsnd_interval*i
the interval value to refine
unsignedintcount
the number of elements in the list of ranges
conststructsnd_interval*ranges
the ranges list
unsignedintmask
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 areevaluated.

Return

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

intsnd_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

structsnd_pcm_runtime*runtime
the pcm runtime instance
unsignedintcond
condition bits
intvar
the variable to evaluate
snd_pcm_hw_rule_func_tfunc
the evaluation function
void*private
the private data pointer passed to function
intdep
the dependent variables
...
variable arguments

Return

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

intsnd_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

structsnd_pcm_runtime*runtime
PCM runtime instance
snd_pcm_hw_param_tvar
hw_params variable to apply the mask
u_int64_tmask
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.

intsnd_pcm_hw_constraint_integer(struct snd_pcm_runtime * runtime, snd_pcm_hw_param_t var)

apply an integer constraint to an interval

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance
snd_pcm_hw_param_tvar
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 anegative error code.

intsnd_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

structsnd_pcm_runtime*runtime
PCM runtime instance
snd_pcm_hw_param_tvar
hw_params variable to apply the range
unsignedintmin
the minimal value
unsignedintmax
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 anegative error code.

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

apply a list of constraints to a parameter

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance
unsignedintcond
condition bits
snd_pcm_hw_param_tvar
hw_params variable to apply the list constraint
conststructsnd_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.

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

apply list of range constraints to a parameter

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance
unsignedintcond
condition bits
snd_pcm_hw_param_tvar
hw_params variable to apply the list of range constraints
conststructsnd_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.

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

apply ratnums constraint to a parameter

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance
unsignedintcond
condition bits
snd_pcm_hw_param_tvar
hw_params variable to apply the ratnums constraint
conststructsnd_pcm_hw_constraint_ratnums*r
struct snd_ratnums constriants

Return

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

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

apply ratdens constraint to a parameter

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance
unsignedintcond
condition bits
snd_pcm_hw_param_tvar
hw_params variable to apply the ratdens constraint
conststructsnd_pcm_hw_constraint_ratdens*r
struct snd_ratdens constriants

Return

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

intsnd_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

structsnd_pcm_runtime*runtime
PCM runtime instance
unsignedintcond
condition bits
unsignedintwidth
sample bits width
unsignedintmsbits
msbits width

Description

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

Return

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

intsnd_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

structsnd_pcm_runtime*runtime
PCM runtime instance
unsignedintcond
condition bits
snd_pcm_hw_param_tvar
hw_params variable to apply the step constraint
unsignedlongstep
step size

Return

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

intsnd_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

structsnd_pcm_runtime*runtime
PCM runtime instance
unsignedintcond
condition bits
snd_pcm_hw_param_tvar
hw_params variable to apply the power-of-2 constraint

Return

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

intsnd_pcm_hw_rule_noresample(struct snd_pcm_runtime * runtime, unsigned int base_rate)

add a rule to allow disabling hw resampling

Parameters

structsnd_pcm_runtime*runtime
PCM runtime instance
unsignedintbase_rate
the rate at which the hardware does not resample

Return

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

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

returnparams fieldvar value

Parameters

conststructsnd_pcm_hw_params*params
the hw_params instance
snd_pcm_hw_param_tvar
parameter to retrieve
int*dir
pointer to the direction (-1,0,1) orNULL

Return

The value for fieldvar if it’s fixed in configuration spacedefined byparams. -EINVAL otherwise.

intsnd_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

structsnd_pcm_substream*pcm
PCM instance
structsnd_pcm_hw_params*params
the hw_params instance
snd_pcm_hw_param_tvar
parameter to retrieve
int*dir
pointer to the direction (-1,0,1) orNULL

Description

Inside configuration space defined byparams remove fromvar allvalues > minimum. Reduce configuration space accordingly.

Return

The minimum, or a negative error code on failure.

intsnd_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

structsnd_pcm_substream*pcm
PCM instance
structsnd_pcm_hw_params*params
the hw_params instance
snd_pcm_hw_param_tvar
parameter to retrieve
int*dir
pointer to the direction (-1,0,1) orNULL

Description

Inside configuration space defined byparams remove fromvar allvalues < maximum. Reduce configuration space accordingly.

Return

The maximum, or a negative error code on failure.

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

a generic PCM ioctl callback

Parameters

structsnd_pcm_substream*substream
the pcm substream instance
unsignedintcmd
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.

voidsnd_pcm_period_elapsed(struct snd_pcm_substream * substream)

update the pcm status for the next period

Parameters

structsnd_pcm_substream*substream
the pcm substream instance

Description

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

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

intsnd_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

structsnd_pcm*pcm
the assigned PCM instance
intstream
stream direction
conststructsnd_pcm_chmap_elem*chmap
channel map elements (for query)
intmax_channels
the max number of channels for the stream
unsignedlongprivate_value
the value passed to each kcontrol’s private_value field
structsnd_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.

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

create a new hwdep instance

Parameters

structsnd_card*card
the card instance
char*id
the id string
intdevice
the device index (zero-based)
structsnd_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 instanceafter this call manually by the caller.

Return

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

voidsnd_pcm_stream_lock(struct snd_pcm_substream * substream)

Lock the PCM stream

Parameters

structsnd_pcm_substream*substream
PCM substream

Description

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

voidsnd_pcm_stream_unlock(struct snd_pcm_substream * substream)

Unlock the PCM stream

Parameters

structsnd_pcm_substream*substream
PCM substream

Description

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

voidsnd_pcm_stream_lock_irq(struct snd_pcm_substream * substream)

Lock the PCM stream

Parameters

structsnd_pcm_substream*substream
PCM substream

Description

This locks the PCM stream likesnd_pcm_stream_lock() and disables the localIRQ (only when nonatomic is false). In nonatomic case, this is identicalassnd_pcm_stream_lock().

voidsnd_pcm_stream_unlock_irq(struct snd_pcm_substream * substream)

Unlock the PCM stream

Parameters

structsnd_pcm_substream*substream
PCM substream

Description

This is a counter-part ofsnd_pcm_stream_lock_irq().

voidsnd_pcm_stream_unlock_irqrestore(struct snd_pcm_substream * substream, unsigned long flags)

Unlock the PCM stream

Parameters

structsnd_pcm_substream*substream
PCM substream
unsignedlongflags
irq flags

Description

This is a counter-part ofsnd_pcm_stream_lock_irqsave().

intsnd_pcm_stop(struct snd_pcm_substream * substream, snd_pcm_state_t state)

try to stop all running streams in the substream group

Parameters

structsnd_pcm_substream*substream
the PCM substream instance
snd_pcm_state_tstate
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.

intsnd_pcm_stop_xrun(struct snd_pcm_substream * substream)

stop the running streams as XRUN

Parameters

structsnd_pcm_substream*substream
the PCM substream instance

Description

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

Return

Zero if successful, or a negative error code.

intsnd_pcm_suspend_all(struct snd_pcm * pcm)

trigger SUSPEND to all substreams in the given pcm

Parameters

structsnd_pcm*pcm
the PCM instance

Description

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

Return

Zero if successful (orpcm isNULL), or a negative error code.

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

Execute PCM ioctl in the kernel-space

Parameters

structsnd_pcm_substream*substream
PCM substream
unsignedintcmd
IOCTL cmd
void*arg
IOCTL argument

Description

The function is provided primarily for OSS layer and USB gadget drivers,and it allows only the limited set of ioctls (hw_params, sw_params,prepare, start, drain, drop, forward).

intsnd_pcm_lib_default_mmap(struct snd_pcm_substream * substream, struct vm_area_struct * area)

Default PCM data mmap function

Parameters

structsnd_pcm_substream*substream
PCM substream
structvm_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.

intsnd_pcm_lib_mmap_iomem(struct snd_pcm_substream * substream, struct vm_area_struct * area)

Default PCM data mmap function for I/O mem

Parameters

structsnd_pcm_substream*substream
PCM substream
structvm_area_struct*area
VMA

Description

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

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

allocate the buffer area according to the given type

Parameters

inttype
the DMA buffer type
structdevice*device
the device pointer
size_tsize
the buffer size to allocate
structsnd_dma_buffer*dmab
buffer allocation record to store the allocated data

Description

Calls the memory-allocator function for the correspondingbuffer type.

Return

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

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

allocate the buffer area according to the given type with fallback

Parameters

inttype
the DMA buffer type
structdevice*device
the device pointer
size_tsize
the buffer size to allocate
structsnd_dma_buffer*dmab
buffer allocation record to store the allocated data

Description

Calls the memory-allocator function for the correspondingbuffer type. When no space is left, this function reduces the size andtries to allocate again. The size actually allocated is stored inres_size argument.

Return

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

voidsnd_dma_free_pages(struct snd_dma_buffer * dmab)

release the allocated buffer

Parameters

structsnd_dma_buffer*dmab
the buffer allocation record to release

Description

Releases the allocated buffer viasnd_dma_alloc_pages().