Re: [PATCH] ALSA: pcm: Release paused streams before suspend if resume is not supported

[Jaroslav Kysela <perex@perex.cz>]

On 02. 04. 25 11:16, Takashi Iwai wrote:

>>>> For my view, the drivers may also receive those triggers:
>>>>
>>>> SNDRV_PCM_TRIGGER_PAUSE_RELEASE_AND_STOP
>>>> SNDRV_PCM_TRIGGER_SUSPEND_IN_PAUSE
>>>> SNDRV_PCM_TRIGGER_RELEASE_IN_PAUSE
>>>>
>>>> This will allow to handle all states properly without any side effects
>>>> (like short unwanted DMA transfers).
>>>>
>>>> The drivers should probably activate those triggers conditionally to
>>>> not break current state sequences.
>>>
>>> Hmm, that looks too complex, IMO.
>>>
>>> Another slightly more straightforward fix would be just to allow the
>>> direct state transition from PAUSED to any state.  Then the remaining
>>> piece is all about driver implementations.  And, this can be
>>> conditionally operated, e.g. only when some extra flag is set.  When
>>> no flag is set, we keep applying PAUSE_RELEASE before the transition
>>> like now, including Peter's patch, that can work generically (but not
>>> always ideally).
>>
>> It looks also feasible. My proposal just allows the straight state
>> identification from the trigger value in the drivers.
> 
> On the second thought, yet another variant would be to introduce only
> one new trigger, SNDRV_PCM_TRIGGER_PAUSE_RESET, for resetting the
> PAUSED state as a step before stopping the stream.  This can be
> applied to all cases for snd_pcm_drop() and snd_pcm_suspend(), too.
> If the driver doesn't support this mode, the PCM core may fall back to
> SNDRV_PCM_TRIGGER_PAUSE_RELEASE.

This looks identical to my proposed SNDRV_PCM_TRIGGER_PAUSE_RELEASE_AND_STOP 
which is more explanatory. It's not clear what PAUSE_RESET should do (probably 
the stream should be kept inactive).

					Jaroslav

-- 
Jaroslav Kysela <perex@perex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.