[PATCH] of: Add generic device tree DMA helpers

On 03/19/2012 09:45 AM, Arnd Bergmann wrote:

On Monday 19 March 2012, Stephen Warren wrote:

quoted

quoted

Maybe one can use named properties in a new device node in that case,
like this:

      bus {
              dma: dma-controller {
                      #dma-cells = <1>;
              };

              device {
                      compatible = "device";
                      channel: dma-channel {
                              type = <0x1>;
                              name = "foo";
                              number = <23>;
                              direction = <3>;
                      };
                      dma-requests = <&dma &channel>;
              };
      };

For reference, this is very similar to how the pinctrl bindings work,
except that they require the "channel" node to be a child of the DMA
controller, and hence "dma-requests" doesn't contain <&dma &channel>,
just <&channel>, since "dma" is the parent (or grand-parent) of "channel".

Right, but the difference beytween the pinctrl binding and what I
describe here is that the channel description would be part of the
dma engine driver specific binding, not the generic binding that
is visible to device drivers.

That's actually true for pinctrl as well: Common pinctrl bindings cover
the content/format of "dma-requests" and a requirement for a
"dma-channel" node, whereas the per-pin-controller bindings define the
content of node "dma-channel".