ALSA: pcm: add comment about application of rule to PCM parameters
authorTakashi Sakamoto <o-takashi@sakamocchi.jp>
Thu, 8 Jun 2017 21:37:06 +0000 (06:37 +0900)
committerTakashi Iwai <tiwai@suse.de>
Thu, 8 Jun 2017 21:40:38 +0000 (23:40 +0200)
commitd81052f92c3d018ade20ecbf461004566428d9a5
tree71ba6190213443d79874d0a609610b1137e3c9e9
parentb81e5ddb159490270fa2cca4f6682c4452035203
ALSA: pcm: add comment about application of rule to PCM parameters

Drivers add rules of parameters to runtime of PCM substream, when
applications open ALSA PCM character device. When applications call
ioctl(2) with SNDRV_PCM_IOCTL_HW_REFINE or SNDRV_PCM_IOCTL_HW_PARAMS, the
rules are applied to the parameters and return the result to user space.

The rule can have dependency between parameters. Additionally, it can have
condition flags about application of rules. Userspace applications can
indicate the flags to suppress change of parameters.

This commit attempts to describe the mechanism.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
sound/core/pcm_native.c