Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750781AbWAJBRE (ORCPT ); Mon, 9 Jan 2006 20:17:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750853AbWAJBRD (ORCPT ); Mon, 9 Jan 2006 20:17:03 -0500 Received: from mail3.uklinux.net ([80.84.72.33]:50562 "EHLO mail3.uklinux.net") by vger.kernel.org with ESMTP id S1750781AbWAJBRC (ORCPT ); Mon, 9 Jan 2006 20:17:02 -0500 Date: Tue, 10 Jan 2006 01:27:18 +0000 From: John Rigg To: David Lang Cc: John Rigg , =?iso-8859-1?Q?Ren=E9?= Rebe , Hannu Savolainen , Jaroslav Kysela , Takashi Iwai , linux-sound@vger.kernel.org, ALSA development , LKML Subject: Re: [Alsa-devel] Re: [OT] ALSA userspace API complexity Message-ID: <20060110012718.GA5375@localhost.localdomain> References: <20050726150837.GT3160@stusta.de> <200601091405.23939.rene@exactcode.de> <200601091812.55943.rene@exactcode.de> <20060109232043.GA5013@localhost.localdomain> <20060110001617.GA5154@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.6+20040907i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 970 Lines: 23 On Mon, Jan 09, 2006 at 04:29:45PM -0800, David Lang wrote: > On Tue, 10 Jan 2006, John Rigg wrote: > > >>does the CPU touch the data for these, or do you DMA directly from > >>userspace (i.e. "zero-copy")? > > > >The cards I mentioned use DMA. RME actually advertises that some of their > >cards can handle 52 channels with zero CPU load. Their onboard DSPs can > >also do routing and mixing, again without touching the CPU. > > I was under the (apparently mistaken) impression that you couldn't DMA > from userspace (something to do with the possibility that the userspace > memory pages could be swapped out in the middle of the DMA) Hmm. Maybe I've been paying too much attention to card vendors' sales talk :) John - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/