// SPDX-License-Identifier: GPL-2.0-or-later /* * Digital Audio (PCM) abstract layer * Copyright (c) by Jaroslav Kysela <[email protected]> * Abramo Bagnara <[email protected]> */ #include <linux/slab.h> #include <linux/sched/signal.h> #include <linux/time.h> #include <linux/math64.h> #include <linux/export.h> #include <sound/core.h> #include <sound/control.h> #include <sound/tlv.h> #include <sound/info.h> #include <sound/pcm.h> #include <sound/pcm_params.h> #include <sound/timer.h> #include "pcm_local.h" #ifdef CONFIG_SND_PCM_XRUN_DEBUG #define CREATE_TRACE_POINTS #include "pcm_trace.h" #else #define trace_hwptr … #define trace_xrun … #define trace_hw_ptr_error … #define trace_applptr … #endif static int fill_silence_frames(struct snd_pcm_substream *substream, snd_pcm_uframes_t off, snd_pcm_uframes_t frames); static inline void update_silence_vars(struct snd_pcm_runtime *runtime, snd_pcm_uframes_t ptr, snd_pcm_uframes_t new_ptr) { … } /* * fill ring buffer with silence * runtime->silence_start: starting pointer to silence area * runtime->silence_filled: size filled with silence * runtime->silence_threshold: threshold from application * runtime->silence_size: maximal size from application * * when runtime->silence_size >= runtime->boundary - fill processed area with silence immediately */ void snd_pcm_playback_silence(struct snd_pcm_substream *substream, snd_pcm_uframes_t new_hw_ptr) { … } #ifdef CONFIG_SND_DEBUG void snd_pcm_debug_name(struct snd_pcm_substream *substream, char *name, size_t len) { … } EXPORT_SYMBOL(…); #endif #define XRUN_DEBUG_BASIC … #define XRUN_DEBUG_STACK … #define XRUN_DEBUG_JIFFIESCHECK … #ifdef CONFIG_SND_PCM_XRUN_DEBUG #define xrun_debug(substream, mask) … #else #define xrun_debug … #endif #define dump_stack_on_xrun(substream) … /* call with stream lock held */ void __snd_pcm_xrun(struct snd_pcm_substream *substream) { … } #ifdef CONFIG_SND_PCM_XRUN_DEBUG #define hw_ptr_error(substream, in_interrupt, reason, fmt, args...) … #else /* ! CONFIG_SND_PCM_XRUN_DEBUG */ #define hw_ptr_error … #endif int snd_pcm_update_state(struct snd_pcm_substream *substream, struct snd_pcm_runtime *runtime) { … } static void update_audio_tstamp(struct snd_pcm_substream *substream, struct timespec64 *curr_tstamp, struct timespec64 *audio_tstamp) { … } static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, unsigned int in_interrupt) { … } /* CAUTION: call it with irq disabled */ int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream) { … } /** * snd_pcm_set_ops - set the PCM operators * @pcm: the pcm instance * @direction: stream direction, SNDRV_PCM_STREAM_XXX * @ops: the operator table * * Sets the given PCM operators to the pcm instance. */ void snd_pcm_set_ops(struct snd_pcm *pcm, int direction, const struct snd_pcm_ops *ops) { … } EXPORT_SYMBOL(…); /** * snd_pcm_set_sync_per_card - set the PCM sync id with card number * @substream: the pcm substream * @params: modified hardware parameters * @id: identifier (max 12 bytes) * @len: identifier length (max 12 bytes) * * Sets the PCM sync identifier for the card with zero padding. * * User space or any user should use this 16-byte identifier for a comparison only * to check if two IDs are similar or different. Special case is the identifier * containing only zeros. Interpretation for this combination is - empty (not set). * The contents of the identifier should not be interpreted in any other way. * * The synchronization ID must be unique per clock source (usually one sound card, * but multiple soundcard may use one PCM word clock source which means that they * are fully synchronized). * * This routine composes this ID using card number in first four bytes and * 12-byte additional ID. When other ID composition is used (e.g. for multiple * sound cards), make sure that the composition does not clash with this * composition scheme. */ void snd_pcm_set_sync_per_card(struct snd_pcm_substream *substream, struct snd_pcm_hw_params *params, const unsigned char *id, unsigned int len) { … } EXPORT_SYMBOL_GPL(…); /* * Standard ioctl routine */ static inline unsigned int div32(unsigned int a, unsigned int b, unsigned int *r) { … } static inline unsigned int div_down(unsigned int a, unsigned int b) { … } static inline unsigned int div_up(unsigned int a, unsigned int b) { … } static inline unsigned int mul(unsigned int a, unsigned int b) { … } static inline unsigned int muldiv32(unsigned int a, unsigned int b, unsigned int c, unsigned int *r) { … } /** * snd_interval_refine - refine the interval value of configurator * @i: the interval value to refine * @v: the interval value to refer to * * 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_refine(struct snd_interval *i, const struct snd_interval *v) { … } EXPORT_SYMBOL(…); static int snd_interval_refine_first(struct snd_interval *i) { … } static int snd_interval_refine_last(struct snd_interval *i) { … } void snd_interval_mul(const struct snd_interval *a, const struct snd_interval *b, struct snd_interval *c) { … } /** * snd_interval_div - refine the interval value with division * @a: dividend * @b: divisor * @c: quotient * * c = a / b * * Returns non-zero if the value is changed, zero if not changed. */ void snd_interval_div(const struct snd_interval *a, const struct snd_interval *b, struct snd_interval *c) { … } /** * snd_interval_muldivk - refine the interval value * @a: dividend 1 * @b: dividend 2 * @k: divisor (as integer) * @c: result * * c = a * b / k * * Returns non-zero if the value is changed, zero if not changed. */ void snd_interval_muldivk(const struct snd_interval *a, const struct snd_interval *b, unsigned int k, struct snd_interval *c) { … } /** * snd_interval_mulkdiv - refine the interval value * @a: dividend 1 * @k: dividend 2 (as integer) * @b: divisor * @c: result * * c = a * k / b * * Returns non-zero if the value is changed, zero if not changed. */ void snd_interval_mulkdiv(const struct snd_interval *a, unsigned int k, const struct snd_interval *b, struct snd_interval *c) { … } /* ---- */ /** * snd_interval_ratnum - refine the interval value * @i: interval to refine * @rats_count: number of ratnum_t * @rats: ratnum_t array * @nump: pointer to store the resultant numerator * @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_ratnum(struct snd_interval *i, unsigned int rats_count, const struct snd_ratnum *rats, unsigned int *nump, unsigned int *denp) { … } EXPORT_SYMBOL(…); /** * snd_interval_ratden - refine the interval value * @i: interval to refine * @rats_count: number of struct ratden * @rats: struct ratden array * @nump: pointer to store the resultant numerator * @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. */ static int snd_interval_ratden(struct snd_interval *i, unsigned int rats_count, const struct snd_ratden *rats, unsigned int *nump, unsigned int *denp) { … } /** * snd_interval_list - refine the interval value from the list * @i: the interval value to refine * @count: the number of elements in the list * @list: the value list * @mask: the bit-mask to evaluate * * 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_list(struct snd_interval *i, unsigned int count, const unsigned int *list, unsigned int mask) { … } EXPORT_SYMBOL(…); /** * snd_interval_ranges - refine the interval value from the list of ranges * @i: the interval value to refine * @count: the number of elements in the list of ranges * @ranges: the ranges list * @mask: the bit-mask to evaluate * * 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_interval_ranges(struct snd_interval *i, unsigned int count, const struct snd_interval *ranges, unsigned int mask) { … } EXPORT_SYMBOL(…); static int snd_interval_step(struct snd_interval *i, unsigned int step) { … } /* Info constraints helpers */ /** * snd_pcm_hw_rule_add - add the hw-constraint rule * @runtime: the pcm runtime instance * @cond: condition bits * @var: the variable to evaluate * @func: the evaluation function * @private: the private data pointer passed to function * @dep: the dependent variables * * Return: Zero if successful, or a negative error code on failure. */ 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, ...) { … } EXPORT_SYMBOL(…); /** * snd_pcm_hw_constraint_mask - apply the given bitmap mask constraint * @runtime: PCM runtime instance * @var: hw_params variable to apply the mask * @mask: the bitmap mask * * Apply the constraint of the given bitmap mask to a 32-bit mask parameter. * * Return: Zero if successful, or a negative error code on failure. */ int snd_pcm_hw_constraint_mask(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var, u_int32_t mask) { … } /** * snd_pcm_hw_constraint_mask64 - apply the given bitmap mask constraint * @runtime: PCM runtime instance * @var: hw_params variable to apply the mask * @mask: the 64bit bitmap mask * * 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_mask64(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var, u_int64_t mask) { … } EXPORT_SYMBOL(…); /** * snd_pcm_hw_constraint_integer - apply an integer constraint to an interval * @runtime: PCM runtime instance * @var: hw_params variable to apply the integer constraint * * 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_integer(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var) { … } EXPORT_SYMBOL(…); /** * snd_pcm_hw_constraint_minmax - apply a min/max range constraint to an interval * @runtime: PCM runtime instance * @var: hw_params variable to apply the range * @min: the minimal value * @max: the maximal value * * 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_minmax(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var, unsigned int min, unsigned int max) { … } EXPORT_SYMBOL(…); static int snd_pcm_hw_rule_list(struct snd_pcm_hw_params *params, struct snd_pcm_hw_rule *rule) { … } /** * snd_pcm_hw_constraint_list - apply a list of constraints to a parameter * @runtime: PCM runtime instance * @cond: condition bits * @var: hw_params variable to apply the list constraint * @l: list * * 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_list(struct snd_pcm_runtime *runtime, unsigned int cond, snd_pcm_hw_param_t var, const struct snd_pcm_hw_constraint_list *l) { … } EXPORT_SYMBOL(…); static int snd_pcm_hw_rule_ranges(struct snd_pcm_hw_params *params, struct snd_pcm_hw_rule *rule) { … } /** * snd_pcm_hw_constraint_ranges - apply list of range constraints to a parameter * @runtime: PCM runtime instance * @cond: condition bits * @var: hw_params variable to apply the list of range constraints * @r: ranges * * 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_ranges(struct snd_pcm_runtime *runtime, unsigned int cond, snd_pcm_hw_param_t var, const struct snd_pcm_hw_constraint_ranges *r) { … } EXPORT_SYMBOL(…); static int snd_pcm_hw_rule_ratnums(struct snd_pcm_hw_params *params, struct snd_pcm_hw_rule *rule) { … } /** * snd_pcm_hw_constraint_ratnums - apply ratnums constraint to a parameter * @runtime: PCM runtime instance * @cond: condition bits * @var: hw_params variable to apply the ratnums constraint * @r: struct snd_ratnums constriants * * 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) { … } EXPORT_SYMBOL(…); static int snd_pcm_hw_rule_ratdens(struct snd_pcm_hw_params *params, struct snd_pcm_hw_rule *rule) { … } /** * snd_pcm_hw_constraint_ratdens - apply ratdens constraint to a parameter * @runtime: PCM runtime instance * @cond: condition bits * @var: hw_params variable to apply the ratdens constraint * @r: struct snd_ratdens 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) { … } EXPORT_SYMBOL(…); static int snd_pcm_hw_rule_msbits(struct snd_pcm_hw_params *params, struct snd_pcm_hw_rule *rule) { … } /** * snd_pcm_hw_constraint_msbits - add a hw constraint msbits rule * @runtime: PCM runtime instance * @cond: condition bits * @width: sample bits width * @msbits: msbits width * * 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_msbits(struct snd_pcm_runtime *runtime, unsigned int cond, unsigned int width, unsigned int msbits) { … } EXPORT_SYMBOL(…); static int snd_pcm_hw_rule_step(struct snd_pcm_hw_params *params, struct snd_pcm_hw_rule *rule) { … } /** * snd_pcm_hw_constraint_step - add a hw constraint step rule * @runtime: PCM runtime instance * @cond: condition bits * @var: hw_params variable to apply the step constraint * @step: step size * * 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) { … } EXPORT_SYMBOL(…); static int snd_pcm_hw_rule_pow2(struct snd_pcm_hw_params *params, struct snd_pcm_hw_rule *rule) { … } /** * snd_pcm_hw_constraint_pow2 - add a hw constraint power-of-2 rule * @runtime: PCM runtime instance * @cond: condition bits * @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_constraint_pow2(struct snd_pcm_runtime *runtime, unsigned int cond, snd_pcm_hw_param_t var) { … } EXPORT_SYMBOL(…); static int snd_pcm_hw_rule_noresample_func(struct snd_pcm_hw_params *params, struct snd_pcm_hw_rule *rule) { … } /** * snd_pcm_hw_rule_noresample - add a rule to allow disabling hw resampling * @runtime: PCM runtime instance * @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_rule_noresample(struct snd_pcm_runtime *runtime, unsigned int base_rate) { … } EXPORT_SYMBOL(…); static void _snd_pcm_hw_param_any(struct snd_pcm_hw_params *params, snd_pcm_hw_param_t var) { … } void _snd_pcm_hw_params_any(struct snd_pcm_hw_params *params) { … } EXPORT_SYMBOL(…); /** * snd_pcm_hw_param_value - return @params field @var value * @params: the hw_params instance * @var: parameter to retrieve * @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_value(const struct snd_pcm_hw_params *params, snd_pcm_hw_param_t var, int *dir) { … } EXPORT_SYMBOL(…); void _snd_pcm_hw_param_setempty(struct snd_pcm_hw_params *params, snd_pcm_hw_param_t var) { … } EXPORT_SYMBOL(…); static int _snd_pcm_hw_param_first(struct snd_pcm_hw_params *params, snd_pcm_hw_param_t var) { … } /** * snd_pcm_hw_param_first - refine config space and return minimum value * @pcm: PCM instance * @params: the hw_params instance * @var: parameter to retrieve * @dir: pointer to the direction (-1,0,1) or %NULL * * 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_first(struct snd_pcm_substream *pcm, struct snd_pcm_hw_params *params, snd_pcm_hw_param_t var, int *dir) { … } EXPORT_SYMBOL(…); static int _snd_pcm_hw_param_last(struct snd_pcm_hw_params *params, snd_pcm_hw_param_t var) { … } /** * snd_pcm_hw_param_last - refine config space and return maximum value * @pcm: PCM instance * @params: the hw_params instance * @var: parameter to retrieve * @dir: pointer to the direction (-1,0,1) or %NULL * * 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_hw_param_last(struct snd_pcm_substream *pcm, struct snd_pcm_hw_params *params, snd_pcm_hw_param_t var, int *dir) { … } EXPORT_SYMBOL(…); /** * snd_pcm_hw_params_bits - Get the number of bits per the sample. * @p: hardware parameters * * Return: The number of bits per sample based on the format, * subformat and msbits the specified hw params has. */ int snd_pcm_hw_params_bits(const struct snd_pcm_hw_params *p) { … } EXPORT_SYMBOL(…); static int snd_pcm_lib_ioctl_reset(struct snd_pcm_substream *substream, void *arg) { … } static int snd_pcm_lib_ioctl_channel_info(struct snd_pcm_substream *substream, void *arg) { … } static int snd_pcm_lib_ioctl_fifo_size(struct snd_pcm_substream *substream, void *arg) { … } static int snd_pcm_lib_ioctl_sync_id(struct snd_pcm_substream *substream, void *arg) { … } /** * snd_pcm_lib_ioctl - a generic PCM ioctl callback * @substream: the pcm substream instance * @cmd: ioctl command * @arg: ioctl argument * * 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. */ int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream, unsigned int cmd, void *arg) { … } EXPORT_SYMBOL(…); /** * snd_pcm_period_elapsed_under_stream_lock() - update the status of runtime for the next period * under acquired lock of PCM substream. * @substream: the instance of pcm substream. * * This function is called when the batch of audio data frames as the same size as the period of * buffer is already processed in audio data transmission. * * The call of function updates the status of runtime with the latest position of audio data * transmission, checks overrun and underrun over buffer, awaken user processes from waiting for * available audio data frames, sampling audio timestamp, and performs stop or drain the PCM * substream according to configured threshold. * * The function is intended to use for the case that PCM driver operates audio data frames under * acquired lock of PCM substream; e.g. in callback of any operation of &snd_pcm_ops in process * context. In any interrupt context, it's preferrable to use ``snd_pcm_period_elapsed()`` instead * since lock of PCM substream should be acquired in advance. * * Developer should pay enough attention that some callbacks in &snd_pcm_ops are done by the call of * function: * * - .pointer - to retrieve current position of audio data transmission by frame count or XRUN state. * - .trigger - with SNDRV_PCM_TRIGGER_STOP at XRUN or DRAINING state. * - .get_time_info - to retrieve audio time stamp if needed. * * Even if more than one periods have elapsed since the last call, you have to call this only once. */ void snd_pcm_period_elapsed_under_stream_lock(struct snd_pcm_substream *substream) { … } EXPORT_SYMBOL(…); /** * snd_pcm_period_elapsed() - update the status of runtime for the next period by acquiring lock of * PCM substream. * @substream: the instance of PCM substream. * * This function is mostly similar to ``snd_pcm_period_elapsed_under_stream_lock()`` except for * acquiring lock of PCM substream voluntarily. * * It's typically called by any type of IRQ handler when hardware IRQ occurs to notify event that * the batch of audio data frames as the same size as the period of buffer is already processed in * audio data transmission. */ void snd_pcm_period_elapsed(struct snd_pcm_substream *substream) { … } EXPORT_SYMBOL(…); /* * Wait until avail_min data becomes available * Returns a negative error code if any error occurs during operation. * The available space is stored on availp. When err = 0 and avail = 0 * on the capture stream, it indicates the stream is in DRAINING state. */ static int wait_for_avail(struct snd_pcm_substream *substream, snd_pcm_uframes_t *availp) { … } pcm_transfer_f; pcm_copy_f; /* calculate the target DMA-buffer position to be written/read */ static void *get_dma_ptr(struct snd_pcm_runtime *runtime, int channel, unsigned long hwoff) { … } /* default copy ops for write; used for both interleaved and non- modes */ static int default_write_copy(struct snd_pcm_substream *substream, int channel, unsigned long hwoff, struct iov_iter *iter, unsigned long bytes) { … } /* fill silence instead of copy data; called as a transfer helper * from __snd_pcm_lib_write() or directly from noninterleaved_copy() when * a NULL buffer is passed */ static int fill_silence(struct snd_pcm_substream *substream, int channel, unsigned long hwoff, struct iov_iter *iter, unsigned long bytes) { … } /* default copy ops for read; used for both interleaved and non- modes */ static int default_read_copy(struct snd_pcm_substream *substream, int channel, unsigned long hwoff, struct iov_iter *iter, unsigned long bytes) { … } /* call transfer with the filled iov_iter */ static int do_transfer(struct snd_pcm_substream *substream, int c, unsigned long hwoff, void *data, unsigned long bytes, pcm_transfer_f transfer, bool in_kernel) { … } /* call transfer function with the converted pointers and sizes; * for interleaved mode, it's one shot for all samples */ static int interleaved_copy(struct snd_pcm_substream *substream, snd_pcm_uframes_t hwoff, void *data, snd_pcm_uframes_t off, snd_pcm_uframes_t frames, pcm_transfer_f transfer, bool in_kernel) { … } /* call transfer function with the converted pointers and sizes for each * non-interleaved channel; when buffer is NULL, silencing instead of copying */ static int noninterleaved_copy(struct snd_pcm_substream *substream, snd_pcm_uframes_t hwoff, void *data, snd_pcm_uframes_t off, snd_pcm_uframes_t frames, pcm_transfer_f transfer, bool in_kernel) { … } /* fill silence on the given buffer position; * called from snd_pcm_playback_silence() */ static int fill_silence_frames(struct snd_pcm_substream *substream, snd_pcm_uframes_t off, snd_pcm_uframes_t frames) { … } /* sanity-check for read/write methods */ static int pcm_sanity_check(struct snd_pcm_substream *substream) { … } static int pcm_accessible_state(struct snd_pcm_runtime *runtime) { … } /* update to the given appl_ptr and call ack callback if needed; * when an error is returned, take back to the original value */ int pcm_lib_apply_appl_ptr(struct snd_pcm_substream *substream, snd_pcm_uframes_t appl_ptr) { … } /* the common loop for read/write data */ snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream, void *data, bool interleaved, snd_pcm_uframes_t size, bool in_kernel) { … } EXPORT_SYMBOL(…); /* * standard channel mapping helpers */ /* default channel maps for multi-channel playbacks, up to 8 channels */ const struct snd_pcm_chmap_elem snd_pcm_std_chmaps[] = …; EXPORT_SYMBOL_GPL(…); /* alternative channel maps with CLFE <-> surround swapped for 6/8 channels */ const struct snd_pcm_chmap_elem snd_pcm_alt_chmaps[] = …; EXPORT_SYMBOL_GPL(…); static bool valid_chmap_channels(const struct snd_pcm_chmap *info, int ch) { … } static int pcm_chmap_ctl_info(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_info *uinfo) { … } /* get callback for channel map ctl element * stores the channel position firstly matching with the current channels */ static int pcm_chmap_ctl_get(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol) { … } /* tlv callback for channel map ctl element * expands the pre-defined channel maps in a form of TLV */ static int pcm_chmap_ctl_tlv(struct snd_kcontrol *kcontrol, int op_flag, unsigned int size, unsigned int __user *tlv) { … } static void pcm_chmap_ctl_private_free(struct snd_kcontrol *kcontrol) { … } /** * snd_pcm_add_chmap_ctls - create channel-mapping control elements * @pcm: the assigned PCM instance * @stream: stream direction * @chmap: channel map elements (for query) * @max_channels: the max number of channels for the stream * @private_value: the value passed to each kcontrol's private_value field * @info_ret: store struct snd_pcm_chmap instance if non-NULL * * Create channel-mapping control elements assigned to the given PCM stream(s). * Return: Zero if successful, or a negative error value. */ 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) { … } EXPORT_SYMBOL_GPL(…);
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