On Thu, 7 Apr 2011, Mian Yousaf Kaukab wrote: > On Wed, Apr 6, 2011 at 5:08 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > >> AFAIK, only mass storage class sets this flag in the kernel and in > >> mass-storage it is already a protocol error if a short-packet arrives > >> when a maxp size packet was expected. > > > > Actually the spec doesn't say how to handle such situations. The > > mass-storage gadgets don't treat it as a protocol error. > > > >> If we don't use short_not_ok, then we will have to wait for each > >> packet to arrive and then based on its size we can set dma. This is > >> what we do if short_not_ok is set to 0. > > > > What's wrong with doing this always? > > Performance reasons mainly. If short_not_ok is set, we can program the > dma for the full buffer length. Otherwise we program it for each > packet. What happens if short_not_ok is set and you program the DMA for the full buffer length, but a short packet arrives? Alan Stern -- 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
