Messages in this thread | | | Subject | Re: [PATCH v7 05/11] dmaengine: Introduce DMA-device device_caps callback | From | Dave Jiang <> | Date | Tue, 14 Jul 2020 09:49:12 -0700 |
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On 7/14/2020 9:29 AM, Serge Semin wrote: > 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.
Hi Sergey. Yes I think that sounds pretty good. Especially seeing there are DMA engines that have channels with different/asymmetric capabilities now.
> > -Sergey >
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