[PATCH V3 1/2] of: Add generic device tree DMA helpers

[Vinod Koul]

On Fri, 2012-07-06 at 13:36 +0200, Guennadi Liakhovetski wrote:
> On Mon, 25 Jun 2012, Arnd Bergmann wrote:
> 
> [snip]
> 
> > The channel data in the device tree is still in a format
> > that is specific to that dmaengine driver and interpreted
> > by it. Using the regular dma_filter_fn prototype is not
> > necessary, but it would be convenient because the dmaengine
> > code already knows how to deal with it. If we don't use this
> > method, how about adding another callback to struct dma_device
> > like
> > 
> > bool (*device_match)(struct dma_chan *chan, struct property *req);
> 
> I like this idea, but why don't we extend it to also cover the non-DT 
> case? I.e., why don't we add the above callback (call it "match" or 
> "filter" or anything else) to dmaengine operations and inside (the 
> extended) dma_request_channel(), instead of calling the filter function, 
> passed as a parameter, we loop over all registered DMAC devices and call 
> their filter callbacks, 
And I have told you many times, that dmacs should not know anything
about clients. They should be totally agnostic to it.

Clients need to request a specific channel, and that is where changes
should come for. Not having dmac provide one.


-- 
~Vinod