From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lee Revell Subject: Re: Trigger Callback Date: Tue, 01 Aug 2006 15:55:19 -0400 Message-ID: <1154462119.14540.73.camel@mindpipe> References: <44CFB014.2050704@blueyonder.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <44CFB014.2050704@blueyonder.co.uk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@lists.sourceforge.net Errors-To: alsa-devel-bounces@lists.sourceforge.net To: Julien Bramary Cc: alsa-devel@lists.sourceforge.net List-Id: alsa-devel@alsa-project.org On Tue, 2006-08-01 at 20:48 +0100, Julien Bramary wrote: > I'm an Alsa beginner and I'm trying to write an alsa driver for an embedded dac on ARM. > > >From Iwai's doc: > > /* trigger callback */ > static int snd_mychip_pcm_trigger(struct snd_pcm_substream *substream, int cmd) > { > switch (cmd) { > case SNDRV_PCM_TRIGGER_START: > // do something to start the PCM engine > break; > case SNDRV_PCM_TRIGGER_STOP: > // do something to stop the PCM engine > break; > default: > return -EINVAL; > } > } > > My question here is, > What are we supposed to do to start the PCM engine? > Because, I'm currently doing nothing, and yet it starts anyway... > I'd like to understand to have more control. "PCM engine" refers to the hardware's PCM engine, not ALSA's. It's 100% device dependent - you need to consult the docs for your sound device to determine how to start the PCM. Lee ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV