Before this goes much further... one fairly obvious and important point must be made. You're designing an API here. You're designing it *WITHOUT* involving the two most important people in its design that there are. The DMA engine maintainers. Is this how we go about designing APIs - behind maintainers backs and then presenting it to the maintainers as a fait accompli? There's 86 messages in this thread, none of which have been copied to them in any way. Why aren't they involved? On Fri, Jun 22, 2012 at 05:52:08PM -0500, Jon Hunter wrote: > Hi Arnd, > > On 06/14/2012 06:48 AM, Arnd Bergmann wrote: > > [snip] > > > This would let us handle the following cases very easily: > > > > 1. one read-write channel > > > > dmas = <&dmac 0x3 match>; > > > > 2. a choice of two read-write channels: > > > > dmas = <&dmacA 0x3 matchA>, <&dmacB 0x3 matchB>; > > > > 3. one read-channel, one write channel: > > > > dmas = <&dmac 0x1 match-read>, <&dmac 0x2 match-write>; > > > > 4. a choice of two read channels and one write channel: > > > > dmas = <&dmacA 0x1 match-readA>, <&dmacA 0x2 match-write> > > <&dmacB match-readB>; > > > > And only the cases where we have more multiple channels that differ > > in more aspects would require named properties: > > > > 5. two different channels > > > > dmas = <&dmac 0x3 match-rwdata>, <&dmac 0x1 match-status>; > > dma-names = "rwdata", "status"; > > > > 6. same as 5, but with a choice of channels: > > > > dmas = <&dmacA 0x3 match-rwdataA>, <&dmacA 0x1 match-status>; > > <dmacB 0x3 match-rwdataB>; > > dma-names = "rwdata", "status", "rwdata"; > > > > > > With a definition like that, we can implement a very simple device > > driver interface for the common cases, and a slightly more complex > > one for the more complex cases: > > > > 1. chan = of_dma_request_channel(dev->of_node, 0); > > 2. chan = of_dma_request_channel(dev->of_node, 0); > > 3. rxchan = of_dma_request_channel(dev->of_node, DMA_MEM_TO_DEV); > > txchan = of_dma_request_channel(dev->of_node, DMA_DEV_TO_MEM); > > 4. rxchan = of_dma_request_channel(dev->of_node, DMA_MEM_TO_DEV); > > txchan = of_dma_request_channel(dev->of_node, DMA_DEV_TO_MEM); > > 5. chan = of_dma_request_named_channel(dev->of_node, "rwdata", 0); > > auxchan = of_dma_request_named_channel(dev->of_node, "status", DMA_DEV_TO_MEM); > > 6. chan = of_dma_request_named_channel(dev->of_node, "rwdata", 0); > > auxchan = of_dma_request_named_channel(dev->of_node, "status", DMA_DEV_TO_MEM); > > In the above examples, did you imply that the of_dma_request_channel() > function would return a type of "struct dma_chan" and so be calling > dma_request_channel() underneath? > > I am been prototyping something, but wanted to make sure I am completely > aligned on this :-) > > Cheers > Jon -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
