On Mon, Dec 17, 2012 at 7:33 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Sun, 16 Dec 2012, Vincent Pelletier wrote: > >> Le dimanche 16 décembre 2012 20:46:38, Vincent Pelletier a écrit : >> > I checked the specs, and the warnings about wMaxPacketSize seem >> > justified (although it's unclear to me wether wMaxPacketSize is >> > restricted to exactly 512B in HS, or only upper-bound at 512B). >> >> Another reply to myself: >> Tested USB device uses a Cypress FX2LP: >> >> http://www.summitsoftconsulting.com/picts/iti_pcb_top.jpg >> >> I checked the FX2LP specs, and endpoint 1 in both directions is hardwired to >> wMaxPacketSize of 64. I believe the FX2LP is quite widespread (judging by the >> availability of a GPL toolchain for it and two CLI tools to send its >> firmware), so those warnings might cause redundant bug reports. > > It does seem odd that people would buy and use these chips even > though they are explicitly in violation of the USB specification. A > device containing one of these things could never pass the USB-CV > verification test. > > It may be possible for xhci-hcd to work around the bug (by internally > changing wMaxPacketSize to 512). > It does not need to be worked around. The fx2 docs specifically say ep1 cannot be used as a bulk endpoint in HS mode. Vincent, RTFM, Cypress has good, downloadable chip docs. Ep1 can either be a legal int/iso endpoint or just not used - all specified in the device/interface descriptors. Nothing in the USB spec requires all device endpoints to be used, or that interfaces have sequentially numbered endpoints. Regards, Steve -- 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
