Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750716AbWCHQSI (ORCPT ); Wed, 8 Mar 2006 11:18:08 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751013AbWCHQSI (ORCPT ); Wed, 8 Mar 2006 11:18:08 -0500 Received: from rwcrmhc14.comcast.net ([216.148.227.154]:62700 "EHLO rwcrmhc14.comcast.net") by vger.kernel.org with ESMTP id S1750716AbWCHQSH (ORCPT ); Wed, 8 Mar 2006 11:18:07 -0500 Message-ID: <440F0396.4050905@comcast.net> Date: Wed, 08 Mar 2006 11:17:26 -0500 From: John Richard Moser User-Agent: Mail/News 1.5 (X11/20060307) MIME-Version: 1.0 To: Jaroslav Kysela CC: linux-kernel@vger.kernel.org Subject: Re: Sound userspace drivers (fishing for insight) References: <440E5746.7070003@comcast.net> In-Reply-To: X-Enigmail-Version: 0.94.0.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2844 Lines: 73 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Jaroslav Kysela wrote: > On Tue, 7 Mar 2006, John Richard Moser wrote: > >> In general, transporting sound data in and out of kernel space is a >> horrid thought. Consider the latencies, which all real-time audio >> people will quickly get angry about. Write sound; context switch; sound >> in driver; context switch back. This over and over? Now we all know >> better than that. > > Nope. If you have a cache coherent architecture like x86, ALSA mmaps > directly the DMA buffer to application and even pointers to this buffer > are mmaped, thus there is no content switch when apps are doing r/w and > there is "zero data copy". The only contents switch is when apps call > poll(), but you should do it, otherwise you'll eat all cpu time. > Awesome. Nice design :) I hath learned today and I woke up 10 minutes ago. >> into the kernel; with alsa it's written to a /proc interface, which > > Using /proc? Where? I've not noticed it :-) I thought that was what /proc/asound/card0/ was for? :) > > Jaroslav > > ----- > Jaroslav Kysela > Linux Kernel Sound Maintainer > ALSA Project, SUSE Labs > - -- All content of all messages exchanged herein are left in the Public Domain, unless otherwise explicitly stated. Creative brains are a valuable, limited resource. They shouldn't be wasted on re-inventing the wheel when there are so many fascinating new problems waiting out there. -- Eric Steven Raymond We will enslave their women, eat their children and rape their cattle! -- Evil alien overlord from Blasto -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2.1 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iQIVAwUBRA8DlQs1xW0HCTEFAQKeqg//SunhyEf8o4MGpQkrrWImJJ5HOaYFragk pgr++6lXTxNTJflpKRO+1iblYCrkakOdLaUn01UZqgaxzquaFEuw9N7bNUpI8Fjn MzS11rYsttZMpfUyT5PiAbMhkiguvBzVv24wcsWwsg83RsH73OZtGGu9BC8SNrw/ jxaJv+B893R6LVIvhMMbRSYAizAEBqfiatttr64G2wNdQ8Hn58fJjStNTyYHFSWo EwsZe19xOW3XgTlRb3S12e6pw9kxDM46/hxpceXB0PwqUtq8kbD8I9Jeb838M3qf XM6+HgXYtSpbJ7zMYVPFI//vo140oHSvK8so0Ifz5NQ561AnqIteDPPKqwJTr02D BqcDZkrXNYoY3qP3rDnTobMciVJycSF6OJp+GHrDxoieV/kKnzjLbvcA4xYU8LmV PZv0/zNX2ZulrKpnVE8MitwurXnhEVZ8NG82ie7V3COu3JyNzAx+uvQCjUIRDef3 ne2icJcyY6kOuWFL0+FslCW1DwyNt9169PEzvJf5Ns590vEwmaxH9u5GfMsjmPHC jmh6zmxNyqSJ05XpWGAeM3iPVgeD0aTqi5dnbXIB7AUF/hmhoCf3co7rQ+y7404g YR7z0vaoK551wCJbkSLa4lnl7oo6lpt8LdS12wIx0c5RGwICTHzCG9uCfAZk+RqX TedLwHW7cfQ= =BSFO -----END PGP SIGNATURE----- - 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/