From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH] of: Add generic device tree DMA helpers Date: Thu, 15 Mar 2012 09:26:52 +0000 Message-ID: <20120315092652.GA16389@n2100.arm.linux.org.uk> References: <4F22DEF2.5000807@ti.com> <1331800690-21518-1-git-send-email-nicolas.ferre@atmel.com> <201203150922.06379.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <201203150922.06379.arnd@arndb.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Arnd Bergmann Cc: Stephen Warren , Benoit Cousson , devicetree-discuss@lists.ozlabs.org, Thierry Reding , Nicolas Ferre , rob.herring@calxeda.com, grant.likely@secretlab.ca, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org On Thu, Mar 15, 2012 at 09:22:06AM +0000, Arnd Bergmann wrote: > On Thursday 15 March 2012, Nicolas Ferre wrote: > > Add some basic helpers to retrieve a DMA controller device_node and the > > DMA request specifications. By making DMA controllers register a generic > > translation function, we allow the management of any type of DMA requests > > specification. > > The void * output of an of_dma_xlate() function that will be implemented > > by the DMA controller can carry any type of "dma-request" argument. > > > > The DMA client will search its associated DMA controller in the list and > > call the registered of_dam_xlate() function to retrieve the request values. > > > > One simple xlate function is provided for the "single number" type of > > request binding. > > > > This implementation is independent from dmaengine so it can also be used > > by legacy drivers. > > > > For legacy reason another API will export the DMA request number into a > > Linux resource of type IORESOURCE_DMA. > > This looks very good. I missed the first version of this patch, but was > thinking of very similar bindings. There's one issue which is concerning me - when we switch OMAP to use DMA engine, it won't use numeric stuff anymore but the DMA engine way of requesting a channel (match function + data). How does that fit into this scheme?