Re: [PATCH 0/2] ALSA: pcm: reinvent the stream synchronization ID API

[Takashi Sakamoto <o-takashi@xxxxxxxxxxxxx>]

On Mon, May 06, 2024 at 05:11:48PM +0200, Jaroslav Kysela wrote:
> Until the commit e11f0f90a626 ("ALSA: pcm: remove SNDRV_PCM_IOCTL1_INFO
> internal command"), there was a possibility to pass information
> about the synchronized streams to the user space. The mentioned
> commit removed blindly the appropriate code with an irrelevant comment.
> 
> The revert may be appropriate, but since this API was lost for several
> years without any complains, it's time to improve it. The hardware
> parameters may change the used stream clock source (e.g. USB hardware)
> so move this synchronization ID to hw_params as read-only field.
> 
> It seems that pipewire can benefit from this API (disable adaptive
> resampling for perfectly synchronized PCM streams) now.
> 
> v1->v2:
>   - remove union usage per Takashi's request
>   - reduce memory usage
>   - use standard ID generation scheme
> 
> Jaroslav Kysela (2):
>   ALSA: pcm: reinvent the stream synchronization ID API
>   ALSA: pcm: optimize and clarify stream sychronization ID API
> 
>  include/sound/pcm.h         | 18 ++++++++++++++++--
>  include/uapi/sound/asound.h | 13 ++++---------
>  sound/core/pcm_lib.c        | 36 ++++++++++++++++++++++++++----------
>  sound/core/pcm_native.c     |  6 ++++++
>  sound/pci/emu10k1/p16v.c    | 17 ++++++++++++-----
>  5 files changed, 64 insertions(+), 26 deletions(-)

I reviewed and added some comments per each.

Anyway, we are at the last week of kernel development process. I think
it better to postpone the discussion about this kind of changes until
releasing -rc1, if people working for the task of quality assurance to
the new kernel release.


Regards

Takashi (not this subsystem maintainer) Sakamoto