On Tue, 2007-11-20 at 12:05 -0800, Roland Dreier wrote: > > Actually, we already established on IRC that the lasi700 driver doesn't > > need this, principally because the parisc architecture doesn't do an > > invalidate for DMA_FROM_DEVICE but a flush and invalidate > > (architecturally, if you read our manuals, even pdc is entitled to write > > back dirty lines, so it's not clear there's actually an invalidate > > instruction we can use). This is also one possible temporary fix for > > the other architectures if we can't get a different method to work > > nicely. > > I think doing a writeback and invalidate is a very fragile way to deal > with DMA into the middle of a data structure. It may work OK for now, > but you have to make sure forever into the future that no codepath > anywhere else ever touches the cacheline that you're DMAing into while > the DMA is pending. It just leaves a hidden trap that is too easy to > step on, because the architectures that get pretty much all testing > all have cache-coherent DMA. > > Reviving my ancient __dma_buffer patch seems far preferable to me. We're talking about trying to fix this for 2.4; which is already at -rc3 ... Is an entire arch change for dma alignment really a merge candidate at this stage? James - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
