On Tue, Jul 14, 2020 at 09:18:16AM -0700, Dave Jiang wrote: > > > On 7/14/2020 9:08 AM, Vinod Koul wrote: > > On 13-07-20, 13:55, Dave Jiang wrote: > > > > > > > > > On 7/10/2020 2:38 AM, Serge Semin wrote: > > > > On Fri, Jul 10, 2020 at 11:45:03AM +0300, Andy Shevchenko wrote: > > > > > On Fri, Jul 10, 2020 at 01:45:44AM +0300, Serge Semin wrote: > > > > > > There are DMA devices (like ours version of Synopsys DW DMAC) which have > > > > > > DMA capabilities non-uniformly redistributed between the device channels. > > > > > > In order to provide a way of exposing the channel-specific parameters to > > > > > > the DMA engine consumers, we introduce a new DMA-device callback. In case > > > > > > if provided it gets called from the dma_get_slave_caps() method and is > > > > > > able to override the generic DMA-device capabilities. > > > > > > > > > > > > > > In light of recent developments consider not to add 'slave' and a such words to the kernel. > > > > > > > > As long as the 'slave' word is used in the name of the dma_slave_caps > > > > structure and in the rest of the DMA-engine subsystem, it will be ambiguous > > > > to use some else terminology. If renaming needs to be done, then it should be > > > > done synchronously for the whole subsystem. > > > > > > What about just calling it dma_device_caps? Consider this is a useful > > > function not only slave DMA will utilize this. I can see this being useful > > > for some of my future code with idxd driver. > > > > Some of the caps may make sense to generic dmaengine but few of them do > > not :) While at it, am planning to make it dmaengine_periph_caps to > > denote that these are dmaengine peripheral capabilities. > > > > If the function only passes in periph_caps, how do we allow the non periph > DMA utilize this function? Hello Dave. That seems reasonable. "dma_device_caps" or even "dma_chan_caps" might be more suitable seeing after this patchset merged in the "dma_slave_caps" may really provide the DMA channel-specific configs. Moreover that structure is accessible only by means of the dma_chan descriptor: int dma_get_slave_caps(struct dma_chan *chan, struct dma_slave_caps *caps); which makes those caps being the channel-specific even without this patchset. So as I see it "dma_chan_caps" might be the better choice. -Sergey
