Hi, On Mon, Apr 04, 2011 at 11:15:28AM -0400, Alan Stern wrote: > > > > HW requests OUT transfers to be aligned on wMaxPacketSize. > > > > > > That doesn't seem to be related to my question: Why are you worrying > > > about short transfers? > > > > not worrying about short transfers per se, I just want gadget driver to > > pass me request->length (for RX/OUT only) which is divisable by > > wMaxPacketSize, so I don't have to keep on guessing what size should I > > use. > > You don't have to guess. Always use request->length. :-) can't in all cases, see below > > See, if gadget passes me request->length which isn't divisible by > > wMaxPacketSize I have two options: > > > > a. round-down: > > That would mean I would need another buffer to receive the > > remaining request->length % ep->maxpacket and later memcpy() > > those remaining bytes to request->buf > > > > b. round-up: > > Simply can't, I don't know if gadget driver has allocated more > > than request->length. > > You left out the correct, third choice: Don't round; use the value you > were asked to use. Like I said before: HW requests me to give lengths which are divisible by wMaxPacketSize. I can't quote parts of the HW docs here, but I *must* give the HW sizes which are divisible by wMaxPacketSize in case of OUT transfers. -- balbi -- 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
