On Tue, 02 Mar 2021 07:29:20 +0100, Anton Yakovlev wrote: > > On 28.02.2021 13:05, Takashi Iwai wrote: > > On Sat, 27 Feb 2021 09:59:56 +0100, > > Anton Yakovlev wrote: > >> > > [snip] > > >> --- a/sound/virtio/virtio_pcm.c > >> +++ b/sound/virtio/virtio_pcm.c > >> @@ -109,6 +109,7 @@ static int virtsnd_pcm_build_hw(struct virtio_pcm_substream *vss, > >> SNDRV_PCM_INFO_BATCH | > >> SNDRV_PCM_INFO_BLOCK_TRANSFER | > >> SNDRV_PCM_INFO_INTERLEAVED | > >> + SNDRV_PCM_INFO_RESUME | > >> SNDRV_PCM_INFO_PAUSE; > > > > Actually you don't need to set SNDRV_PCM_INFO_RESUME. > > This flag means that the driver supports the full resume procedure, > > which isn't often the case; with this, the driver is supposed to > > resume the stream exactly from the suspended position. > > > > Most drivers don't set this but implement only the suspend-stop > > action. Then the application (or the sound backend) will re-setup the > > stream and restart accordingly. > > I tried to resume driver without SNDRV_PCM_INFO_RESUME, and alsa-lib > called only ops->prepare(). It makes sense for a typical hw, but we have > "clean" unconfigured device on resume. And we must set hw parameters as > a first step. It means, that code should be more or less the same. And > maybe it's better to set SNDRV_PCM_INFO_RESUME, since it allows us to > resume substream in any situation (regardless of application behavior). > I can refactor code to only send requests from trigger(RESUME) path and > not to call ops itself. It should make code more straitforward. What do > you say? How about calling hw_params(NULL) conditionally in the prepare? Doing the full stack work in the trigger callback is bad from the API design POV; in general the trigger callback is supposed to be as short as possible. Takashi
