From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takashi Iwai Subject: Re: [RFC PATCH 1/4] ALSA: core: let low-level driver or userspace disable rewinds Date: Wed, 08 Jul 2015 16:21:16 +0200 Message-ID: References: <1436350236-17509-1-git-send-email-pierre-louis.bossart@linux.intel.com> <1436350236-17509-2-git-send-email-pierre-louis.bossart@linux.intel.com> Mime-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) by alsa0.perex.cz (Postfix) with ESMTP id 5890D26154E for ; Wed, 8 Jul 2015 16:21:16 +0200 (CEST) In-Reply-To: <1436350236-17509-2-git-send-email-pierre-louis.bossart@linux.intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Pierre-Louis Bossart Cc: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org On Wed, 08 Jul 2015 12:10:33 +0200, Pierre-Louis Bossart wrote: > > 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. > > 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) The forward should also fail with such hardware, no? Takashi > > Signed-off-by: Pierre-Louis Bossart > --- > 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 691e7ee..25310b7 100644 > --- a/include/sound/pcm.h > +++ b/include/sound/pcm.h > @@ -370,6 +370,7 @@ 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 a45be6b..b62b162 100644 > --- a/include/uapi/sound/asound.h > +++ b/include/uapi/sound/asound.h > @@ -356,6 +356,7 @@ 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 d126c03..a70e52d 100644 > --- a/sound/core/pcm_native.c > +++ b/sound/core/pcm_native.c > @@ -543,6 +543,8 @@ 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; > > bits = snd_pcm_format_physical_width(runtime->format); > runtime->sample_bits = bits; > @@ -2428,6 +2430,9 @@ 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; > + > snd_pcm_stream_lock_irq(substream); > switch (runtime->status->state) { > case SNDRV_PCM_STATE_PREPARED: > @@ -2476,6 +2481,9 @@ static snd_pcm_sframes_t snd_pcm_capture_rewind(struct snd_pcm_substream *substr > if (frames == 0) > return 0; > > + if (runtime->no_rewinds) > + return 0; > + > snd_pcm_stream_lock_irq(substream); > switch (runtime->status->state) { > case SNDRV_PCM_STATE_PREPARED: > -- > 1.9.1 > > _______________________________________________ > Alsa-devel mailing list > Alsa-devel@alsa-project.org > http://mailman.alsa-project.org/mailman/listinfo/alsa-devel >