From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756160Ab3DVOyt (ORCPT ); Mon, 22 Apr 2013 10:54:49 -0400 Received: from moutng.kundenserver.de ([212.227.126.187]:62064 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756144Ab3DVOyr (ORCPT ); Mon, 22 Apr 2013 10:54:47 -0400 From: Arnd Bergmann To: "Lars-Peter Clausen" Subject: Re: [PATCH 1/2] dma: of: Remove restriction that #dma-cells can't be 0 Date: Mon, 22 Apr 2013 16:54:37 +0200 User-Agent: KMail/1.12.2 (Linux/3.8.0-18-generic; KDE/4.3.2; x86_64; ; ) Cc: Vinod Koul , Jon Hunter , linux-kernel@vger.kernel.org References: <1366619613-30639-1-git-send-email-lars@metafoo.de> <201304221438.15945.arnd@arndb.de> <51753170.2050902@metafoo.de> In-Reply-To: <51753170.2050902@metafoo.de> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Message-Id: <201304221654.38159.arnd@arndb.de> X-Provags-ID: V02:K0:5w9BJeMiDpV6MZ2QSVCscXgWCwDlK3FjgYNPl0HEMOb LAGv8qbZWJp5+bPNBwmFPo2llRtQ0Y3mMRN2yuNe7LRgy7FQUc G63d9PxDHteFXSB8UGu3F0Rm6+BbL8en7DBHIQ2mfCQTW4GxsH jGmHEjSR9F8MaDGISpIBaHBjSlB1mg0jYO5L/uN4Csyxc2VzBt ZuJ6HUV/OWoYwzX7e90jSGQdD6LvKvdALNKMFUVGu+fSHHFy6n wrwm9CpIfl7qP2PWXeVO7MkqtKKAH1/L2gKXO6S8yfnN+t/MVS vQJDx7LGTgmtiSQeWEID3ixgPTHJKB7agDudqMmkce2bVBcpWO LO9kxyb2joAQeLnkA5dI= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday 22 April 2013, Lars-Peter Clausen wrote: > > On 04/22/2013 02:38 PM, Arnd Bergmann wrote: > > On Monday 22 April 2013, Lars-Peter Clausen wrote: > >> > >> There is no sensible reason why #dma-cells shouldn't be allowed to be 0. It is > >> completely up to the DMA controller how many additional parameters, besides the > >> phandle, it needs to identify a channel. E.g. for DMA controller with only one > >> channel or for DMA controllers which don't have a restriction on which channel > >> can be used for which peripheral it completely legitimate to not require any > >> additional parameters. > >> > >> Also fixes the following warning: > >> drivers/dma/of-dma.c: In function 'of_dma_controller_register': > >> drivers/dma/of-dma.c:67:7: warning: 'nbcells' may be used uninitialized in this function > >> > >> Signed-off-by: Lars-Peter Clausen > > > > Do you have an example for this? If a dma engine has only one request line, > > why would you even use the dmaengine subsystem for it, rather than including > > the code to program it in the slave driver? > > Why wouldn't I use the dmaengine subsystem for a DMA controller? In my > particular case different instances of the same DMA core will be used with > different DMA slaves. And the DMA slaves can also have different DMA master > cores, depending on the system. Right, that makes sense. Acked-by: Arnd Bergmann