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Wed, 9 Jun 2021 17:27:37 +0200 (CEST) Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id 9C33DF8020D for ; Wed, 9 Jun 2021 17:27:30 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 9C33DF8020D Authentication-Results: alsa1.perex.cz; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b="H79RKqTy"; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b="6oT1iruu" Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id DB6C51FD61; Wed, 9 Jun 2021 15:27:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1623252449; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=4CBvrzeOzxy4KJljb2MRTkBdJceVWyPh75kn83SPyEg=; 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charset=US-ASCII Cc: alsa-devel@alsa-project.org, clemens@ladisch.de X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" On Wed, 09 Jun 2021 16:31:43 +0200, Takashi Sakamoto wrote: > > Current implementation of ALSA PCM core has a kernel API, > snd_pcm_period_elapsed(), for drivers to awaken user processes from waiting > for available frames. The function voluntarily acquires lock of PCM > substream, therefore it is not called in process context for any PCM > operation since the lock is already acquired. > > It is convenient for packet-oriented driver, at least for drivers to audio > and music unit in IEEE 1394 bus. The drivers are allowed by Linux > FireWire subsystem to process isochronous packets queued till recent > isochronous cycle in process context in any time. > > This commit adds snd_pcm_period_elapsed() variant, > snd_pcm_period_elapsed_without_lock(), for drivers to call in the > process context. > > Signed-off-by: Takashi Sakamoto > --- > include/sound/pcm.h | 1 + > sound/core/pcm_lib.c | 71 ++++++++++++++++++++++++++++++++++---------- > 2 files changed, 57 insertions(+), 15 deletions(-) > > diff --git a/include/sound/pcm.h b/include/sound/pcm.h > index 2e1200d17d0c..bae90696cd06 100644 > --- a/include/sound/pcm.h > +++ b/include/sound/pcm.h > @@ -1066,6 +1066,7 @@ void snd_pcm_set_ops(struct snd_pcm * pcm, int direction, > void snd_pcm_set_sync(struct snd_pcm_substream *substream); > int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream, > unsigned int cmd, void *arg); > +void snd_pcm_period_elapsed_under_stream_lock(struct snd_pcm_substream *substream); > void snd_pcm_period_elapsed(struct snd_pcm_substream *substream); > snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream, > void *buf, bool interleaved, > diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c > index b7e3d8f44511..3488ec1e3674 100644 > --- a/sound/core/pcm_lib.c > +++ b/sound/core/pcm_lib.c > @@ -1778,27 +1778,41 @@ int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream, > EXPORT_SYMBOL(snd_pcm_lib_ioctl); > > /** > - * snd_pcm_period_elapsed - update the pcm status for the next period > - * @substream: the pcm substream instance > + * snd_pcm_period_elapsed_under_stream_lock() - update the status of runtime for the next period > + * under acquired lock of PCM substream. > + * @substream: the instance of pcm substream. > + * > + * This function is called when the batch of audio data frames as the same size as the period of > + * buffer is already processed in audio data transmission. > + * > + * The call of function updates the status of runtime with the latest position of audio data > + * transmission, checks overrun and underrun over buffer, awaken user processes from waiting for > + * available audio data frames, sampling audio timestamp, and performs stop or drain the PCM > + * substream according to configured threshold. > + * > + * The function is intended to use for the case that PCM driver operates audio data frames under > + * acquired lock of PCM substream; e.g. in callback of any operation of &snd_pcm_ops in process > + * context. In any interrupt context, it's preferrable to use ``snd_pcm_period_elapsed()`` instead > + * since lock of PCM substream should be acquired in advance. > * > - * This function is called from the interrupt handler when the > - * PCM has processed the period size. It will update the current > - * pointer, wake up sleepers, etc. > + * Developer should pay enough attention that some callbacks in &snd_pcm_ops are done by the call of > + * function: > * > - * Even if more than one periods have elapsed since the last call, you > - * have to call this only once. > + * - .pointer - to retrieve current position of audio data transmission by frame count or XRUN state. > + * - .trigger - with SNDRV_PCM_TRIGGER_STOP at XRUN or DRAINING state. > + * - .get_time_info - to retrieve audio time stamp if needed. > + * > + * Even if more than one periods have elapsed since the last call, you have to call this only once. > + * > + * Context: Any context in which lock of PCM substream is already acquired. This function may not > + * sleep. Hm, this text still remains here. Overlooked? Takashi