[Sound-open-firmware] [alsa-devel] [PATCH v5 05/14] ASoC: SOF: Add PCM operations support

[Takashi Iwai]

On Tue, 09 Apr 2019 18:11:07 +0200,
Pierre-Louis Bossart wrote:
> 
> 
> 
> On 4/9/19 10:48 AM, Takashi Iwai wrote:
> > On Tue, 09 Apr 2019 16:23:17 +0200,
> > Pierre-Louis Bossart wrote:
> >>
> >>
> >>> ok, thanks for confirming. we'll remove the INFO_RESUME flag in SOF
> >>> and follow-up with the removal on all other Intel drivers. Thanks
> >>> for enlightening us on this.
> >>
> >> Actually one more question related to the documentation, which reads
> >>
> >> "Note that the trigger with SUSPEND can always be called when
> >> snd_pcm_suspend_all() is called, regardless of the
> >> SNDRV_PCM_INFO_RESUME flag. The RESUME flag affects only the behavior
> >> of snd_pcm_resume(). (Thus, in theory, SNDRV_PCM_TRIGGER_RESUME isn’t
> >> needed to be handled in the trigger callback when no
> >> SNDRV_PCM_INFO_RESUME flag is set. But, it’s better to keep it for
> >> compatibility reasons.)"
> >>
> >> I could not figure out what the last sentence means. It's my
> >> understanding that the resume_trigger will never be called with the
> >> code flow below when INFO_RESUME isn't declared. Would you mind
> >> clarifying what this compatibility might be? Thanks!
> >
> > Well, in the above "better to keep it" text -- here "it" was meant as
> > SNDRV_PCM_TRIGGER_RESUME case handling in the trigger callback, not as
> > SNDRV_PCM_INFO_RESUME flag.  That is, the above recommends a trigger
> > callback like below would keep SNDRV_PCM_TRIGGER_RESUME although it
> > won't be called practically:
> 
> That's the part that I find odd. we keep the TRIGGER_RESUME but it
> will never be called, that's an unreachable/untestable switch case,
> no? Or we should trap it as an error case.

It's just for consistency.  But it might look confusing, yeah.


Takashi