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Thu, 30 Jan 2020 02:06:45 -0500 (EST) Date: Thu, 30 Jan 2020 16:06:43 +0900 From: Takashi Sakamoto To: Pierre-Louis Bossart Message-ID: <20200130070642.GA7741@workstation> Mail-Followup-To: Pierre-Louis Bossart , sylvain.bertrand@gmail.com, alsa-devel@alsa-project.org References: <20200129232340.GA23769@freedom> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Cc: alsa-devel@alsa-project.org, sylvain.bertrand@gmail.com Subject: Re: [alsa-devel] no period wakeup support 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" On Wed, Jan 29, 2020 at 05:43:19PM -0600, Pierre-Louis Bossart wrote: > > Nowadays, is this reasonable to consider disabling the period wakeup as default > > instead of expecting period wakeup by default? > > I'd say yes - it's been nearly 10 years since this capability was added, and > it's quite common across HDaudio, Chrome, Android plaforms. > > But considering this as a default doesn't mean it's available in 100% of the > cases, you still you need to check that > > a) the driver is capable of disabling the period wakeup > b) the driver is capable of providing a precise position outside of period > elapsed events (usually marked with the INFO_BATCH capability). > > alsa-lib gives you the means to query both cases. > > Note that you also have the case where you cannot disable interrupts but can > still use timer-based solutions (e.g. for USB audio). I suspect this advice. In design of ALSA PCM core, runtime of PCM substream is configured for the mode of no-period-wakeup just in a case that userspace application requests it[1]. As long as developers take enough care of compatibility for existent applications, it's better to support period wakeup for each IRQ as a default, then support no-period-wakeup mode as an option. [1] https://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git/tree/sound/core/pcm_native.c#n715 Regards Takashi Sakamoto _______________________________________________ Alsa-devel mailing list Alsa-devel@alsa-project.org https://mailman.alsa-project.org/mailman/listinfo/alsa-devel