[PATCH] ALSA: compress: allow pause and resume during draining

[Takashi Iwai]

On Mon, 26 Oct 2020 10:18:38 +0100,
Gyeongtaek Lee wrote:
> 
> With a stream with low bitrate, user can't pause or resume the stream
> near the end of the stream because current ALSA doesn't allow it.
> If the stream has very low bitrate enough to store whole stream into
> the buffer, user can't do anything except stop the stream and then
> restart it from the first because most of applications call draining
> after sending last frame to the kernel.
> If pause, resume are allowed during draining, user experience can be
> enhanced.
> To prevent malfunction in HW drivers which don't support pause
> during draining, pause during draining will only work if HW driver
> enable this feature explicitly by calling
> snd_compr_use_pause_in_draining().
> 
> Signed-off-by: Gyeongtaek Lee <gt82.lee at samsung.com>
> Cc: stable at vger.kernel.org

Could you restart the new thread?  It's been hanging too deeply and
hard to read through.

Since it's the revised patch, please give the revision number (v2 or
such) and show what's different from the previous patches.

About the changes:

> +/**
> + * snd_compr_use_pause_in_draining - Allow pause and resume in draining state
> + * @substream: compress substream to set
> + *
> + * Allow pause and resume in draining state.
> + * Only HW driver supports this transition can call this API.
> + */
> +static inline void snd_compr_use_pause_in_draining(
> +					struct snd_compr_stream *substream)
> +{
> +	substream->device->use_pause_in_draining = true;
> +}

How to set the flag is an open question.  A natural way would be to
set it somehow at creating the component object, but currently there
seems no way to pass any flags.


thanks,

Takashi