--- On Fri, 6/18/10, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > usb-storage uses the scatter-gather library, which either > constructs a > separate URB for each buffer in an SG list, or else passes > the entire > list down to the HCD in a single URB (if the HCD supports > scatterlist operation). IMO such low-level details obfuscate the goal... > > Doesn't the storage driver do exactly that? It builds > > a single transfer out of multiple buffers. It seems to > me > > that we can build a single transfer out of multiple > > buffers provided all but the last buffers meet some > > size constraint. > > The requirement is that each scatterlist buffer except the > last must be > a multiple of the maxpacket length. Right; it's been so long since I did that work that I forgot about those details; sorry; (Plus the ability to give a scatterlist to an HCD is pretty new, yes?) > doesn't work out > so well with Wireless USB, where the maxpacket length can > be something > weird like 1536 or 3072. Then the only way to handle > it is to use > bounce buffers. Or for NCM ... perhaps, as I noted, the MTU can be tweaked so that the SKBs always fit. -- 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
