On Sat, Aug 08, 2015 at 10:03:43AM +0100, Russell King - ARM Linux wrote: > On Fri, Aug 07, 2015 at 08:28:57PM -0400, Peter Hurley wrote: > > Even dma_get_slave_caps() returns _true_ for cmd_pause support; ok, that > > interface is pointless. > > How about reporting that as a bug then, because if you look back in the > git history, as you are fully capable of, you will find that the slave > capability stuff went in _after_ omap-dma, and *many* DMA engine drivers > have not been updated. Here, let me do _your_ work for you: > > commit cb8cea513c80db1dfe2dce468d2d0772005bb9a1 > Author: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx> > Date: Mon Nov 17 14:42:04 2014 +0100 > > dmaengine: Create a generic dma_slave_caps callback > > commit 2dcdf570936168d488acf90be9b04a3d32dafce7 > Author: Peter Ujfalusi <peter.ujfalusi@xxxxxx> > Date: Fri Sep 14 15:05:45 2012 +0300 > > dmaengine: omap: Add support for pause/resume in cyclic dma mode > > Oh look, omap-dma pre-dates the creation of dma_slave_caps by over two > years! > > However, it's *not* as trivial as you think: the dma_slave_caps() call > has no knowledge whether a channel will be used in cyclic mode or not, > or which direction it will be used. So, it really _can't_ report > whether pause mode is supported or not. So actually, this is something > that can't be fixed trivially, and was a detail missed when the slave > caps was reviewed (I probably missed the review or missed the point.) The API queries the capabilities for a channel. So a channel has been allocated. BUT it would not imply the direction as that is descriptor based, so should we query the capabilities for a descriptor and use those in clients ? Also the current dma_slave_caps() has been moved to framework and reports based on driver callbacks. Now we have a hardware which supports pause for one direction only so we should model it bit differently Thoughts... ?? -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
