On Tue, Jun 30, 2015 at 6:50 AM, Peter Chen <Peter.Chen@xxxxxxxxxxxxx> wrote: > >> On Tue, Jun 30, 2015 at 12:33 AM, Steve Calfee <stevecalfee@xxxxxxxxx> >> wrote: >> > On Mon, Jun 29, 2015 at 7:16 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> >> wrote: >> >> On Mon, 29 Jun 2015, Peter Chen wrote: >> >> >> >>> Just like Steve pointed, it should be a ZLT problem, do you have >> >>> below patch in your tree, and the host may not send zlt, but you may >> >>> queue an zero-length request, the f_hid does not set req->zero flag >> >>> either. >> >>> >> >>> commit 953c66469735aed8d2ada639a72b150f01dae605 >> >>> Author: Abbas Raza <Abbas_Raza@xxxxxxxxxx> >> >>> Date: Thu Jul 17 19:34:31 2014 +0800 >> >>> >> >>> usb: chipidea: udc: Disable auto ZLP generation on ep0 >> >>> >> >>> >> >>> If it still has problem, send me apps if possible (with needed >> >>> kernel patches). >> >> >> >> Note that a UDC should _never_ queue an extra zero-length packet for >> >> an OUT transfer, no matter how req->zero is set. In other words, >> >> req->zero is supposed to affect only IN transfers. >> >> >> > Yes UDC gadgets receive packets sent by the host on OUT transfers. If >> > ZLT transfers are needed for the protocol, a short transfer is needed >> > to end an OUT sequence and it must be sent by the sender, in this case >> > the host. The UDC should detect receiving a zero length EP0 OUT and >> > that signals the end of the 64 byte transfer from host to gadget. >> > >> > Regards, Steve >> >> Thanks Alan, Peter and Steve for your help and quick response. >> >> In fact, today I tested with a similar patch i.e. have QH_IOS and QH_ZLT set for >> control endpoint in udc.c. The 64 byte transfer appears to work fine. >> >> I am not sure whether this is the ideal solution, Testing some more to ensure >> that there are no regressions. I will send out an update in about a day. >> > > The most probably is the QH_ZLT bit, your tree may not the patch I mentioned > above. The QH_IOS only affects a setup being received. > > Peter Sure, I will test this and update closure on this issue. Cheers, Jayan -- 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
