Thanks Alan, I shall implement the solution & get back. Controller is ChipIdea. Thanks, Chiru. On Wed, Aug 12, 2009 at 8:02 PM, Alan Stern<stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Wed, 12 Aug 2009, velempati Chiranjeevi wrote: > >> Hi, >> >> I figured the actual cause of the issue.But I am not sure about the >> implementation of the solution. >> >> >> In the gadget framework, When the host sends the set_config command, >> the set_alt of all the functions are called. >> >> In the mass storage , the set_alt function raises an exception and >> returns 0.The endpoints are enabled as part of the do_set_config, >> triggered the handle_exception. But by the time the endpoints >> corresponding to mass storage are enabled, we get a command from the >> host as a part of the USB MS CV test.Since the endpoints are not >> enabled by now, the UDC driver doesn't send an ack. So the test fails. >> >> >> Can the endpoints be enabled as part of the interrupt context ? > > I don't think so. But it doesn't matter, because that's not the real > problem. > > The cause of the failure is that the host sends a command before the > Set-Config has finished. Assuming that the host is working okay, this > means the device controller completes the status stage of the > Set-Config request before the endpoints have been enabled, i.e., before > do_set_config() returns. > > However, if you look at standard_setup_req() in file_storage.c, you'll > see that the USB_REQ_SET_CONFIGURATION case sets value to > DELAYED_STATUS. This means that fsg_setup() won't call ep0_queue(). > > Now, the device controller driver is supposed to delay the status stage > of a control transfer until an explicit response is queued for ep0. > (See the kerneldoc description of control endpoints under > usb_ep_queue() in include/linux/usb/gadget.h.) That response is queued > by handle_exception() in the FSG_STATE_CONFIG_CHANGE case, where the > code calls ep0_queue() after do_set_config() returns. > > Hence the real problem lies in the device controller driver, not in > g_file_storage. The driver carries out the status stage before it is > supposed to. You didn't say which controller driver you are using, > so I can't tell you how to fix it. > > 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
