From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753222Ab2CHKu0 (ORCPT ); Thu, 8 Mar 2012 05:50:26 -0500 Received: from mga14.intel.com ([143.182.124.37]:31007 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751146Ab2CHKuZ (ORCPT ); Thu, 8 Mar 2012 05:50:25 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="scan'208";a="116314189" Subject: Re: [PATCH/RFC] dmaengine: add a slave parameter to __dma_request_channel() From: Vinod Koul To: Guennadi Liakhovetski Cc: Russell King - ARM Linux , linux-kernel@vger.kernel.org, "'Jassi Brar'" , Linus Walleij , Magnus Damm , Paul Mundt In-Reply-To: References: <1331101687.24656.319.camel@vkoul-udesk3> <20120307093026.GM17370@n2100.arm.linux.org.uk> <20120307103112.GP17370@n2100.arm.linux.org.uk> <20120307124620.GT17370@n2100.arm.linux.org.uk> <20120307142634.GA18787@n2100.arm.linux.org.uk> <20120307162755.GB18787@n2100.arm.linux.org.uk> <1331188201.4657.51.camel@vkoul-udesk3> Content-Type: text/plain; charset="UTF-8" Date: Thu, 08 Mar 2012 16:25:28 +0530 Message-ID: <1331204128.4657.54.camel@vkoul-udesk3> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2012-03-08 at 11:16 +0100, Guennadi Liakhovetski wrote: > I still have the impression, that my specific use-case (sh-mobile), where > channels can be freely configured for use by _ANY_ client on one of > _SEVERAL_ DMAC instances, is not fully understood or taken into account. > For this driver any kind of fixed mapping means, that we'd have to use > both virtual channels and controllers, adding _a lot_ of complexity to the > DMAC driver and making the dmaengine core just an "obfuscation layer." > Yes, I remember Russell proposing core helpers for this. They would help, > but (1) when would they be available, (2) how well would they be suitable > for us, (3) they'd take the coding / maintainance burden away, but > wouldn't reduce complexity and run-time overhead. Lets try to address you case as well. On a typical platform 1) how many dma controllers you have? 2) how many clients you have 3) which client can use what controller channel? How is mapping decided, do you have a mux, is it hard wired by soc designers,....? Can you pls give a description so that we ensure all models fit in the final solution? -- ~Vinod