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ALSA: core: selection of audio_tstamp type and accuracy reports

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Audio timestamps can be extracted from sample counters, wall clocks,
PHC clocks (Ethernet AVB), on-demand synchronized snapshots. This
patch provides the ability to report timestamping capabilities, select
timestamp types and retrieve timestamp accuracy, if supported.
Details can be found in Documentations/sound/alsa/timestamping.txt

This functionality is introduced by reclaiming the reserved_aligned
field introduced by commit9c7066aef4a5eb8e4063de28f06c508bf6f2963a
in snd_pcm_status to provide userspace with selection/query capabilities.
Additional driver_tstamp and audio_tstamp_accuracy fields are also added.

snd_pcm_mmap_status remains a read-only structure with only
the audio timestamp value accessible from user space. The selection
of audio timestamp type is done through snd_pcm_status only

This commit does not impact ABI and does not impact the default
behavior. By default audio timestamp is aligned with hw_pointer and
reports the DMA position. Backwards compatibility is handled by using
the HDAudio wall clock for playback and the hw_ptr for all other
cases.

For timestamp selection a new STATUS_EXT ioctl is introduced with
read/write parameters. Alsa-lib will be modified to make use of
STATUS_EXT.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Pierre-Louis Bossart
2015-02-13 15:14:03 -06:00
committed by Takashi Iwai
parent 0c8d948565
commit 229d043096
3 changed files with 290 additions and 4 deletions
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60
include/sound/pcm.h
View File

@@ -60,6 +60,9 @@ struct snd_pcm_hardware {
struct snd_pcm_substream;
struct snd_pcm_audio_tstamp_config; /* definitions further down */
struct snd_pcm_audio_tstamp_report;
struct snd_pcm_ops {
int (*open)(struct snd_pcm_substream *substream);
int (*close)(struct snd_pcm_substream *substream);
@@ -281,6 +284,58 @@ struct snd_pcm_hw_constraint_ranges {
struct snd_pcm_hwptr_log;
/*
* userspace-provided audio timestamp config to kernel,
* structure is for internal use only and filled with dedicated unpack routine
*/
struct snd_pcm_audio_tstamp_config {
/* 5 of max 16 bits used */
u32 type_requested:4;
u32 report_delay:1; /* add total delay to A/D or D/A */
};
static inline void snd_pcm_unpack_audio_tstamp_config(__u32 data,
struct snd_pcm_audio_tstamp_config *config)
{
config->type_requested = data & 0xF;
config->report_delay = (data >> 4) & 1;
}
/*
* kernel-provided audio timestamp report to user-space
* structure is for internal use only and read by dedicated pack routine
*/
struct snd_pcm_audio_tstamp_report {
/* 6 of max 16 bits used for bit-fields */
/* for backwards compatibility */
u32 valid:1;
/* actual type if hardware could not support requested timestamp */
u32 actual_type:4;
/* accuracy represented in ns units */
u32 accuracy_report:1; /* 0 if accuracy unknown, 1 if accuracy field is valid */
u32 accuracy; /* up to 4.29s, will be packed in separate field */
};
static inline void snd_pcm_pack_audio_tstamp_report(__u32 *data, __u32 *accuracy,
const struct snd_pcm_audio_tstamp_report *report)
{
u32 tmp;
tmp = report->accuracy_report;
tmp <<= 4;
tmp |= report->actual_type;
tmp <<= 1;
tmp |= report->valid;
*data &= 0xffff; /* zero-clear MSBs */
*data |= (tmp << 16);
*accuracy = report->accuracy;
}
struct snd_pcm_runtime {
/* -- Status -- */
struct snd_pcm_substream *trigger_master;
@@ -361,6 +416,11 @@ struct snd_pcm_runtime {
struct snd_dma_buffer *dma_buffer_p; /* allocated buffer */
/* -- audio timestamp config -- */
struct snd_pcm_audio_tstamp_config audio_tstamp_config;
struct snd_pcm_audio_tstamp_report audio_tstamp_report;
struct timespec driver_tstamp;
#if defined(CONFIG_SND_PCM_OSS) || defined(CONFIG_SND_PCM_OSS_MODULE)
/* -- OSS things -- */
struct snd_pcm_oss_runtime oss;