[PATCH] of: Add generic device tree DMA helpers

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

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?