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author | Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> | 2015-02-13 15:14:03 -0600 |
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committer | Takashi Iwai <tiwai@suse.de> | 2015-02-20 17:30:03 +0100 |
commit | 229d043096ea8e58829d37d35767afeac15997f5 (patch) | |
tree | 36a7c15f53435696812cd8e616769f373400d027 /sound/core/pcm_native.c | |
parent | 0c8d948565490d2a2db9d9a5aec388342c7d38ce (diff) | |
download | op-kernel-dev-229d043096ea8e58829d37d35767afeac15997f5.zip op-kernel-dev-229d043096ea8e58829d37d35767afeac15997f5.tar.gz |
ALSA: core: selection of audio_tstamp type and accuracy reports
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>
Diffstat (limited to 'sound/core/pcm_native.c')
0 files changed, 0 insertions, 0 deletions