From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [PATCH V3 1/2] of: Add generic device tree DMA helpers Date: Tue, 24 Jul 2012 10:04:53 -0600 Message-ID: <500EC7A5.6020907@wwwdotorg.org> References: <1335820679-28721-1-git-send-email-jon-hunter@ti.com> <201207171924.33756.arnd@arndb.de> <500DC255.40900@wwwdotorg.org> <201207240719.03601.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <201207240719.03601.arnd@arndb.de> Sender: linux-omap-owner@vger.kernel.org To: Arnd Bergmann Cc: Vinod Koul , linux-arm-kernel@lists.infradead.org, Stephen Warren , Benoit Cousson , device-tree , Nicolas Ferre , Rob Herring , Grant Likely , Jassi Brar , Jon Hunter , Russell King - ARM Linux , dan.j.williams@intel.com, linux-omap List-Id: devicetree@vger.kernel.org On 07/24/2012 01:19 AM, Arnd Bergmann wrote: > On Monday 23 July 2012, Stephen Warren wrote: >>> 3. A device with three channels, one of which has two alternatives: >> >> s/three/four/ s/one of which/both of which/ >> >> This binding doc seems reasonable to me. > > I asked a linguist about it who said that you can't have "both" together > with "four". She also mentioned that my text is rather confusing, so maybe > you also got it wrong. I'll try adding some explanation: Oops, I guess I meant s/three/two/ :-) It seems that given there are two values for dma-names, there really are two channels; it's just that one channel is bi-directional, and the second has two alternatives. Still, I guess you could also view this as three separate channels instead. In which case, the text below makes sense. > 3. A device with three channels, one of which has two alternatives: > > dmas = <&dma0 1 4 /* first channel, data read */ > &dma0 2 6 /* second channel, data write */ > &dma1 1 0 /* third channel, error read */ > &dma2 1 0>; /* third channel, ernative error read */ > dma-names = "data", "data", "error", "error"; > > The first two channels are identified by having a unique direction > flag in combination with the "data" string. For the third channel, > there are two dma specifiers with identical flags (1) and strings > ("error"), so only one specifier may be used at a time.