Hi Vladimir,
On Friday 03 May 2013 02:00:29 Vladimir Zapolskiy wrote:
> On 05/03/13 01:18, Laurent Pinchart wrote:
> > On Friday 03 May 2013 01:13:48 Vladimir Zapolskiy wrote:
> >> This change removes redundant calls to uvc_function_connect() and
> >> uvc_function_disconnect() on V4L2 device node open and release.
> >>
> >> These two functions attemp to control pull-up on D+ line directly,
> >> however such an action should be performed by an UDC iteself, and within
> >> the gadget there is no information about current mode of the controller.
> >>
> >> The UDC may be in suspended state, or an OTG controller may be in host
> >> mode, therefore it seems better not to try to forcibly pull-up D+ line
> >> on open() syscall.
> >
> > OK, but we then need to fix the problem properly. The UVC gadget must not
> > appear connected until an application opens the corresponding device.
> > Likewise, it must disconnect from the bus when the application closes the
> > device. How can this be guaranteed properly ?
>
> For better understanding of the issue, could you explain briefly why do you
> prefer to have the gadget not connected to the bus, if device node is not
> opened?
As soon as the gadget will connect to the bus the device will be enumerated by
the host and bound to a host driver that will query the device using UVC-
specific requests. The userspace application is involved in replying to those
requests, so it needs to be bound to the device on the gadget side or the
initialization process on the host side will fail.
> >> Signed-off-by: Vladimir Zapolskiy<vladimir_zapolskiy@xxxxxxxxxx>
> >> Cc: Laurent Pinchart<laurent.pinchart@xxxxxxxxxxxxxxxx>
> >> ---
> >>
> >> drivers/usb/gadget/uvc_v4l2.c | 5 -----
> >> 1 file changed, 5 deletions(-)
> >>
> >> diff --git a/drivers/usb/gadget/uvc_v4l2.c
> >> b/drivers/usb/gadget/uvc_v4l2.c
> >> index ad48e81..e2b66e1 100644
> >> --- a/drivers/usb/gadget/uvc_v4l2.c
> >> +++ b/drivers/usb/gadget/uvc_v4l2.c
> >> @@ -132,20 +132,15 @@ uvc_v4l2_open(struct file *file)
> >>
> >> handle->device =&uvc->video;
> >> file->private_data =&handle->vfh;
> >>
> >> - uvc_function_connect(uvc);
> >>
> >> return 0;
> >>
> >> }
> >>
> >> static int
> >> uvc_v4l2_release(struct file *file)
> >> {
> >>
> >> - struct video_device *vdev = video_devdata(file);
> >> - struct uvc_device *uvc = video_get_drvdata(vdev);
> >>
> >> struct uvc_file_handle *handle =
> >> to_uvc_file_handle(file->private_data);
> >> struct uvc_video *video = handle->device;
> >>
> >> - uvc_function_disconnect(uvc);
> >> -
> >>
> >> uvc_video_enable(video, 0);
> >> uvc_free_buffers(&video->queue);
--
Regards,
Laurent Pinchart
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