Vinod Koul <vinod.koul@xxxxxxxxx> writes: > On Fri, Jul 24, 2015 at 10:28:45AM +0200, Lars-Peter Clausen wrote: >> I don' think we need set set and clear functions. We need them for >> the ACK flag because the ACK flag can be set later on. But the REUSE >> flag should be specified when the descriptor is created so the >> driver can make the necessary preparations it might need to support >> re-usable descriptors. Maybe we should call the flag >> DMA_PREP_REUSABLE (like the other DMA_PREP_*) flag to reflect this. > The flow I have depicted is that descriptor prepare should not be linked to > it's reuse. The submit operation specifies if a descriptor can be reused or > not, so driver knows what to do after txn completion > While reusing if client wants to stop reusing it can clear reuse flag and > submit so that descriptor is freed up I think the same way as Vinod. Giving the dmaengine user the flexibility to reuse or not the descriptor is great. Moreover, this flexibility will extend to userspace, as some dmaengine users, such as v4l2, don't know if a descriptor will be reused : it's a userspace decision whever to requeue the transmission or not, up to the driver. > Also this is tied to caps so you are allowed to do so only if caps supports > it. From these points we do need set/clear/test_reuse APIs +1. Cheers. -- Robert -- 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
