On Fri, Sep 30, 2016 at 03:22:40PM +0200, Takashi Iwai wrote:
> On Fri, 30 Sep 2016 14:43:24 +0200,
> Subhransu S. Prusty wrote:
> >
> > From: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
> >
> > Add new hw_params flag to explicitly tell driver that rewinds will never
> > be used. This can be used by low-level driver to optimize DMA operations
> > and reduce power consumption. Use this flag only when data written in
> > ring buffer will never be invalidated, e.g. any update of appl_ptr is
> > final.
> >
> > Note that the update of appl_ptr include both a read/write data
> > operation as well as snd_pcm_forward() whose behavior is not modified.
> >
> > Caveat: there is currently no way to query capabilities without opening
> > a pcm stream, so applications might need to serially open all exposed
> > devices, check what they support by looking at hw_params->info and close
> > them (this is what PulseAudio does so might not be an issue)
>
> This is a general issue in the current PCM API design, and not
> specific to this new bit.
Will remove this from commit message.
>
> > Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
> > Signed-off-by: Ramesh Babu <ramesh.babu@xxxxxxxxx>
> > Signed-off-by: Vinod Koul <vinod.koul@xxxxxxxxx>
> > Signed-off-by: Subhransu S. Prusty <subhransu.s.prusty@xxxxxxxxx>
> > ---
> > include/sound/pcm.h | 1 +
> > include/uapi/sound/asound.h | 1 +
> > sound/core/pcm_native.c | 8 ++++++++
> > 3 files changed, 10 insertions(+)
> >
> > diff --git a/include/sound/pcm.h b/include/sound/pcm.h
> > index af1fb37..5344c16 100644
> > --- a/include/sound/pcm.h
> > +++ b/include/sound/pcm.h
> > @@ -368,6 +368,7 @@ struct snd_pcm_runtime {
> > unsigned int rate_num;
> > unsigned int rate_den;
> > unsigned int no_period_wakeup: 1;
> > + unsigned int no_rewinds:1;
> >
> > /* -- SW params -- */
> > int tstamp_mode; /* mmap timestamp is updated */
> > diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h
> > index 609cadb..6828ed2 100644
> > --- a/include/uapi/sound/asound.h
> > +++ b/include/uapi/sound/asound.h
> > @@ -362,6 +362,7 @@ typedef int snd_pcm_hw_param_t;
> > #define SNDRV_PCM_HW_PARAMS_NORESAMPLE (1<<0) /* avoid rate resampling */
> > #define SNDRV_PCM_HW_PARAMS_EXPORT_BUFFER (1<<1) /* export buffer */
> > #define SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP (1<<2) /* disable period wakeups */
> > +#define SNDRV_PCM_HW_PARAMS_NO_REWINDS (1<<3) /* disable rewinds */
> >
> > struct snd_interval {
> > unsigned int min, max;
> > diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> > index c61fd50..be8617b 100644
> > --- a/sound/core/pcm_native.c
> > +++ b/sound/core/pcm_native.c
> > @@ -565,6 +565,8 @@ static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
> > runtime->no_period_wakeup =
> > (params->info & SNDRV_PCM_INFO_NO_PERIOD_WAKEUP) &&
> > (params->flags & SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP);
> > + runtime->no_rewinds =
> > + (params->flags & SNDRV_PCM_HW_PARAMS_NO_REWINDS) ? 1 : 0;
> >
> > bits = snd_pcm_format_physical_width(runtime->format);
> > runtime->sample_bits = bits;
> > @@ -2438,6 +2440,9 @@ static snd_pcm_sframes_t snd_pcm_playback_rewind(struct snd_pcm_substream *subst
> > if (frames == 0)
> > return 0;
> >
> > + if (runtime->no_rewinds)
> > + return 0;
>
> Better to return an error instead?
As the number of frames rewinded is zero, it looks appropriate. Any reason
why returning an error code would help?
Regards,
Subhransu
--
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