Re: [PATCH] ALSA: uapi: pcm: control the filling of the silence samples for drain

[Takashi Iwai <tiwai@suse.de>]

On Tue, 02 May 2023 13:55:36 +0200,
Jaroslav Kysela wrote:
> 
> Introduce SNDRV_PCM_INFO_PERFECT_DRAIN and SNDRV_PCM_HW_PARAMS_NO_DRAIN_SILENCE
> flags to fully control the filling of the silence samples in the drain ioctl.
> Actually, the configurable silencing is going to be implemented in the user
> space [1], but drivers (hardware) may not require this operation. Those flags
> do the bidirectional setup for this operation:
> 
> 1) driver may notify the presence of the perfect drain
> 2) user space may not require the filling of the silence samples to inhibit clicks
> 
> If we decide to move this operation to the kernel space in future, the
> SNDRV_PCM_INFO_PERFECT_DRAIN flag may handle this situation without
> double "silence" processing (user + kernel space).
> 
> The ALSA API should be universal, so forcing the behaviour (modifying of
> the ring buffer with any samples) for the drain operation is not ideal.
> 
> [1] https://lore.kernel.org/alsa-devel/20230502115010.986325-1-perex@perex.cz/
> 
> Signed-off-by: Jaroslav Kysela <perex@perex.cz>

Now applied to for-next branch (with a typo fix in the comment).


thanks,

Takashi