Am Dienstag, 16. Februar 2010 15:12:45 schrieb Shilimkar, Santosh: > > > > I am afraid for these controllers the controller driver must be responsible > > > > for all DMA and cache issues. Indicating the exact requirements to the > > > > upper layer would be a battle already lost. > > > > so the safe choice is not to set has_dma and the generic layer will leave > > > > the issue to the lower level. > > > This means don't use dma at all which will almost kill the performance. > > > > Why would you be unable to map a buffer in the hcd driver when you know > > that you'll use DMA? > Probably it can be. The USB stack has the dma maintenance code at common > place for all controllers and hence we were just trying to see if there is > way to handle that way. This is true. If you can find a clean way to describe your requirements to the generic layer, that would be better. The problem is that we must not end up with a dozen flags. Your original patch however kills ehci, ohci and uhci on some architectures. Regards Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
