From mboxrd@z Thu Jan 1 00:00:00 1970 From: Clemens Ladisch Subject: Re: pcm prepare Date: Tue, 28 Jul 2015 08:56:43 +0200 Message-ID: <55B727AB.8090902@ladisch.de> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from dehamd003.servertools24.de (dehamd003.servertools24.de [31.47.254.18]) by alsa0.perex.cz (Postfix) with ESMTP id 0316B260459 for ; Tue, 28 Jul 2015 08:56:44 +0200 (CEST) In-Reply-To: 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: Andy Ng , alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org Andy Ng wrote: > I am quite surprised that by sending hardware params with alsa-lib the > prepare function is called automatically in the driver. > > In my case, I would like to open and configure pcmNp and pcmNc and > then call prepare for pcmNp and pcmPc channels. > > It is quite imperative to execute specific configuration steps after > both channels are opened and configured. What configuration steps? Is there some dependency or shared resource between the two streams? In that case, you have to set the SNDRV_PCM_INFO_JOINT_DUPLEX flag, and do whatever is necessary in the first hw_params call, and just check for correctness in the later hw_params call of the other stream. > I was wondering if there is any ioctl interface that can be hooked in > alsa-lib to pass extra configuration info before start the streams. No. Regards, Clemens