device - usb: why my f_uvc doesn't answer GET_DEF request? -

i need implement uvc1.5 spec in device, choose linux3.4 kernel, , want use drivers/usb/gadget/webcam.c function driver. doesn't function properly.

according signals captured wireshark, when host sends get_def request device, device answer -enoent results in failure enumeration.

i find out when composite.c receives kind of requests, forward them f->set_up continue.

the main part of f->set_up is:

    uvc->event_setup_out = !(ctrl->brequesttype & usb_dir_in);     uvc->event_length = le16_to_cpu(ctrl->wlength);      memset(&v4l2_event, 0, sizeof(v4l2_event));     v4l2_event.type = uvc_event_setup;     memcpy(&uvc_event->req, ctrl, sizeof(uvc_event->req));     v4l2_event_queue(&uvc->vdev, &v4l2_event); 

the call of v4l2_event_queue puzzles me: handle event? didn't see code doing such event related initialization work.....

and question how handle event properly, can answer get_def request ?

it's v4l2 event should deal in place. can receive v4l2 event through

rt = ioctl(dev->fd, vidioc_dqevent,&v4l2_event); 

then can parse v4l2_event, maybe get_cur, ger_len,etc. can response requests define.