From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Hofman Subject: Re: Direct use of the DMA buffer? Date: Mon, 20 Feb 2012 10:25:57 +0100 Message-ID: <4F4211A5.7050104@ivitera.com> References: <4F4181AF.1060303@ivitera.com> <4F420017.70508@ladisch.de> <4F420694.6040902@ivitera.com> <4F4210A6.8010902@perex.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from cable.insite.cz (static-84-242-75-189.net.upcbroadband.cz [84.242.75.189]) by alsa0.perex.cz (Postfix) with ESMTP id 98A79246EE for ; Mon, 20 Feb 2012 10:25:59 +0100 (CET) In-Reply-To: <4F4210A6.8010902@perex.cz> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: Jaroslav Kysela Cc: alsa-devel List-Id: alsa-devel@alsa-project.org Dne 20.2.2012 10:21, Jaroslav Kysela napsal(a): >> >> Clemens, thanks a lot for the information. How does it work when the >> alsa-lib chain contains plugins, such as plug, rate, etc.? I would >> assume the application circumvents these. > > Nope. The mmap commit mechanism was introduced to keep the plugin > interface functional. The direct mmap access to the DMA buffer is only > applied for the direct hw: devices. If a plugin is used inside alsa-lib, > the application talks to the plugin chain (it means that an intermediate > buffer for samples can be allocated to let things working). > Jaroslav, thanks a lot for the clarification. Pavel.