From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Dan Williams" Subject: Re: [PATCH 07/13] dmaengine: introduce dma_request_channel and private channels Date: Thu, 18 Dec 2008 10:27:56 -0700 Message-ID: References: <20081114213300.32354.1154.stgit@dwillia2-linux.ch.intel.com> <20081114213453.32354.53002.stgit@dwillia2-linux.ch.intel.com> <129600E5E5FB004392DDC3FB599660D70C8F3406@irsmsx504.ger.corp.intel.com> <129600E5E5FB004392DDC3FB599660D70C984F6A@irsmsx504.ger.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , "hskinnemoen@atmel.com" , "g.liakhovetski@gmx.de" , "nicolas.ferre@atmel.com" To: "Sosnowski, Maciej" Return-path: Received: from wa-out-1112.google.com ([209.85.146.179]:59359 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751046AbYLRR16 (ORCPT ); Thu, 18 Dec 2008 12:27:58 -0500 In-Reply-To: <129600E5E5FB004392DDC3FB599660D70C984F6A@irsmsx504.ger.corp.intel.com> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: On Thu, Dec 18, 2008 at 7:33 AM, Sosnowski, Maciej wrote: > What about situation, where some or all "public" channels in the system > have been claimed by one client for its exclusive usage > before another client appears trying to use available "public" channels? > Despite of presence in the system of channels that supposed to be "public", > the second cilent realizes that the channels are not available anymore at all > or at least limited... > Doesn't it contradict the general idea of "public" (general purpose) channels? > If a greedy module comes along and grabs all the channels via dma_request_channel() then yes, there will be nothing left for the public pool. So, there is a requirement to "play nice". If this becomes an issue in practice we could add a DMA_NO_PRIVATE flag to reserve a channel for public-only usage. Regards, Dan