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. Regards, 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
