On Sun, 30 May 2010, saeed bishara wrote: > Hi, > I'm newbie to usb, and came across an issue when using USB NEC > testing device, this device sends 128 bytes string descriptor, but as > the usb_string_sub tries first to ask for 255 bytes, the transaction > never completes. is it legal for the device to send 128 bytes string? Yes. > if yes, should the host controller (orion-ehci) detect data > completion? Yes, if the device works properly. If the entire descriptor is 128 bytes (that is, 2 bytes for the descriptor header plus 126 bytes for the string data) then it is a multiple of the maxpacket size. In such cases the device needs to send a zero-length packet at the end of the descriptor. Without that zero-length packet, the controller cannot detect that the transfer is complete. Of course, the transfer should time out after 10 seconds or so. 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
