From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754550AbYISPI3 (ORCPT ); Fri, 19 Sep 2008 11:08:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751503AbYISPIW (ORCPT ); Fri, 19 Sep 2008 11:08:22 -0400 Received: from de01egw02.freescale.net ([192.88.165.103]:64502 "EHLO de01egw02.freescale.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750987AbYISPIV (ORCPT ); Fri, 19 Sep 2008 11:08:21 -0400 Message-ID: <48D3BEB2.3060902@freescale.com> Date: Fri, 19 Sep 2008 10:01:06 -0500 From: Timur Tabi User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv:1.8.1.16) Gecko/20080702 SeaMonkey/1.1.11 MIME-Version: 1.0 To: "linux-os (Dick Johnson)" CC: Haavard Skinnemoen , Dan Williams , lkml Subject: Re: dmaengine.c: question about device_alloc_chan_resources References: <48D02589.8070601@freescale.com> <20080918162826.3a9d9429@hskinnemo-gx745.norway.atmel.com> <48D2664D.7040204@freescale.com> <20080918164535.5e9f77a8@hskinnemo-gx745.norway.atmel.com> <20080919132544.533ab7d0@hskinnemo-gx745.norway.atmel.com> <48D3B880.3070607@freescale.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org linux-os (Dick Johnson) wrote: > On Fri, 19 Sep 2008, Timur Tabi wrote: > >> Haavard Skinnemoen wrote: >> >>> Yes, or maybe provide an interface for simply requesting a channel >>> without having to register any callbacks. >> I could use this feature. The sound drivers for our MPC8610 processor use DMA, >> but the drivers need to control the DMA hardware directly, so I can't use >> dmaengine. I would like to be able to just reserve the channels and program >> them as I see fit. >> >> -- >> Timur Tabi >> Linux kernel developer at Freescale > > The hardware on the PC/AT machines won't allow you to > reserve a specific channel and program it as you see fit, > because there are two devices, one for the low DMA > channels and another for the high ones. True, but that restriction doesn't apply to all processors. So we could still provide the capability of reserving channels for those systems where it makes sense. This is the case for the DMA controller I'm working with. My solution for now is to permanently reserve the channels I need. This is safe and probably okay, because there are 6 other channels still available. However, if there was a mechanism where I could dynamically reserve channels, I would use it. > The information transmitted in this message is confidential and may be privileged. Really? -- Timur Tabi Linux kernel developer at Freescale