On Wednesday 18 November 2015 16:41:35 Peter Ujfalusi wrote: > On 11/18/2015 04:29 PM, Arnd Bergmann wrote: > > On Wednesday 18 November 2015 16:21:26 Peter Ujfalusi wrote: > >> 2. non slave channel requests, where only the functionality matters, like > >> memcpy, interleaved, memset, etc. > >> We could have a simple: > >> dma_request_channel(mask); > >> > >> But looking at the drivers using dmaengine legacy dma_request_channel() API: > >> Some sets DMA_INTERRUPT or DMA_PRIVATE or DMA_SG along with DMA_SLAVE: > >> drivers/misc/carma/carma-fpga.c DMA_INTERRUPT|DMA_SLAVE|DMA_SG > >> drivers/misc/carma/carma-fpga-program.c DMA_MEMCPY|DMA_SLAVE|DMA_SG > >> drivers/media/platform/soc_camera/mx3_camera.c DMA_SLAVE|DMA_PRIVATE > >> sound/soc/intel/common/sst-firmware.c DMA_SLAVE|DMA_MEMCPY > >> > >> as examples. > >> Not sure how valid are these... I just had a look myself. carma has been removed fortunately in linux-next, so we don't have to worry about that any more. I assume that the sst-firmware.c case is a mistake, it should just use a plain DMA_SLAVE and not DMA_MEMCPY. Aside from these, everyone else uses either DMA_CYCLIC in addition to DMA_SLAVE, which seems valid, or they use DMA_PRIVATE, which I think is redundant in slave drivers and can be removed. > > It's usually not much harder to separate out the legacy case from > > the normal dma_request_slave_channel_reason(), so those drivers don't > > really need to use the unified compat API. > > The current dma_request_slave_channel()/_reason() is not the 'legacy' API. > Currently there is no way to get the reason why the dma channel request fails > when using the _compat() version of the API, which is used by drivers which > can be used in DT or in legacy mode as well. Sure, they all could have local > if(){}else{} for handling this, but it is not a nice thing. > > As it was discussed instead of adding the _reason() version for the _compat > call, we should simplify the dmaengine API for getting the channel and at the > same time we will have ERR_PTR returned instead of NULL. What I meant was that we don't need to handle them with the unified simple interface. The users of DMA_CYCLIC can just keep using an internal helper that only deals with the legacy case, or use dma_request_slave() or whatever is the new API for the DT case. Arnd -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html