Hi Michael, On Thursday 24 January 2013 11:22:02 Michael Grzeschik wrote: > The current implementation of the composite framework connects the > gadget function to the device-controller at kernel boottime. > > It's possible that the userspace application, which handles the > enumeration requests of the gadget, starts with high latency when the > host did already gave up to detect the gadget. In that case the > gadget-application will not work in the first case. This shouldn't happen, as the UVC gadget driver should start disconnected (it calls usb_function_deactive() in uvc_function_bind()). If the host can enumerate the gadget before the application starts it would then likely be a device controller driver bug, not a UVC gadget driver bug. > To ensure that the device acts properly with application start, we reset > the connection on device open, so the host restarts its enumeration > requests for the gadget. > > Signed-off-by: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx> > --- > > Another approach could be, to connect the composite to the > device-controller only at open of the v4l2 device. As the composite > framework is generic, this could probably not be true for every > function. > > drivers/usb/gadget/uvc_v4l2.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/usb/gadget/uvc_v4l2.c b/drivers/usb/gadget/uvc_v4l2.c > index 2ca9386..068d6a7 100644 > --- a/drivers/usb/gadget/uvc_v4l2.c > +++ b/drivers/usb/gadget/uvc_v4l2.c > @@ -16,6 +16,7 @@ > #include <linux/list.h> > #include <linux/mutex.h> > #include <linux/videodev2.h> > +#include <linux/usb/gadget.h> > #include <linux/vmalloc.h> > #include <linux/wait.h> > > @@ -122,6 +123,7 @@ uvc_v4l2_open(struct file *file) > struct video_device *vdev = video_devdata(file); > struct uvc_device *uvc = video_get_drvdata(vdev); > struct uvc_file_handle *handle; > + struct usb_composite_dev *cdev = uvc->func.config->cdev; > > handle = kzalloc(sizeof(*handle), GFP_KERNEL); > if (handle == NULL) > @@ -130,6 +132,9 @@ uvc_v4l2_open(struct file *file) > v4l2_fh_init(&handle->vfh, vdev); > v4l2_fh_add(&handle->vfh); > > + usb_gadget_disconnect(cdev->gadget); > + usb_gadget_connect(cdev->gadget); > + > handle->device = &uvc->video; > file->private_data = &handle->vfh; -- Regards, Laurent Pinchart -- 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
