On Mon, Nov 18, 2013 at 02:31:54PM +0000, Arnd Bergmann wrote: > On Monday 18 November 2013, Mark Rutland wrote: > > > +++ b/Documentation/devicetree/bindings/dma/mpc512x-dma.txt > > > @@ -0,0 +1,55 @@ > > > +* Freescale MPC512x DMA Controller > > > + > > > +The DMA controller in the Freescale MPC512x SoC can move blocks of > > > +memory contents between memory and peripherals or memory to memory. > > > + > > > +Refer to the "Generic DMA Controller and DMA request bindings" > > > description > > > +in the dma.txt file for a more detailled discussion of the binding. The > > > +MPC512x DMA engine binding follows the common scheme, but doesn't provide > > > +support for the optional channels and requests counters (those values are > > > +derived from the detected hardware features) and has a fixed client > > > +specifier length of 1 integer cell (the value is the DMA channel, since > > > +the DMA controller uses a fixed assignment of request lines per channel). > > > > The fact that #dma-cells must be <1> isn't a difference from the > > standard binding, and needs not be described here. The meaning of the > > value should be in your description of #dma-cells below. > > I think the value it has to be in there, and I have in the past asked other > people to add this. Note that in the generic binding, it says that it must > be "at least 1". You can have controllers that require a larger number, or > that can use 1 or 2 alternatively, depending on how the device is wired > up, e.g. when a dma controller has two master ports you would need a > second cell to specify the port number, but only if more than one port > is actually connected to a slave.
The number of cells required should be described. My points were that it should be described at the property description rather than in the introduction, and that the fact that a specific value was required was not a difference from the bindings as the paragraph implied. > > > I'm not sure it's worth mentioning optional channels / request counters. > > If anything, it would be better to update dma.txt to move the "Optional > > properties" to something like "Suggested properties"... > > These are less clearly defined. In the generic binding, it's mostly a matter > of "if you need to pass this information, use these properties". The > individual > binding can then make them mandatory if needed. Agreed. I'd prefer that bindings described the suggested properties they used, rather than those they don't. Thanks, Mark. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
