Hi Bhupesh,
Thanks for the patch. Just a couple of small comments.
On Tuesday 31 July 2012 06:24:52 Bhupesh Sharma wrote:
> This patch adds the support in UVC webcam gadget design for providing
> USB_GADGET_DELAYED_STATUS in response to a set_interface(alt setting 1)
> command issue by the Host.
>
> The current UVC webcam gadget design generates a STREAMON event
> corresponding to a set_interface(alt setting 1) command from the Host.
> This STREAMON event will eventually be routed to a real V4L2 device.
>
> To start video streaming, it may be required to perform some register
> writes to a camera sensor device over slow external busses like I2C or SPI.
> So, it makes sense to ensure that we delay the STATUS stage of the
> set_interface(alt setting 1) command.
>
> Otherwise, a lot of ISOC IN tokens sent by the Host will be replied to
> by zero-length packets by the webcam device. On certain Hosts this may even
> lead to ISOC URBs been cancelled from the Host side.
>
> So, as soon as we finish doing all the "streaming" related stuff on the
> real V4L2 device, we call a STREAMON ioctl on the UVC side and from here we
> call the 'usb_composite_setup_continue' function to complete the status
> stage of the set_interface(alt setting 1) command.
>
> Further, we need to ensure that we queue no video buffers on the UVC
> webcam gadget, until we de-queue a video buffer from the V4L2 device.
> So, the application should call the STREAMON on UVC side only when it has
> dequeued sufficient buffers from the V4L2 side and queued them to the
> UVC gadget.
>
> Signed-off-by: Bhupesh Sharma <bhupesh.sharma@xxxxxx>
> ---
> drivers/usb/gadget/f_uvc.c | 16 +++++++++++-----
> drivers/usb/gadget/uvc.h | 1 +
> drivers/usb/gadget/uvc_v4l2.c | 15 ++++++++++++++-
> 3 files changed, 26 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/usb/gadget/f_uvc.c b/drivers/usb/gadget/f_uvc.c
> index 2a8bf06..22f7570 100644
> --- a/drivers/usb/gadget/f_uvc.c
> +++ b/drivers/usb/gadget/f_uvc.c
> @@ -272,6 +272,13 @@ uvc_function_setup(struct usb_function *f, const struct
> usb_ctrlrequest *ctrl) return 0;
> }
>
> +void uvc_function_setup_continue(struct uvc_device *uvc)
> +{
> + struct usb_composite_dev *cdev = uvc->func.config->cdev;
> +
> + usb_composite_setup_continue(cdev);
> +}
> +
> static int
> uvc_function_get_alt(struct usb_function *f, unsigned interface)
> {
> @@ -334,7 +341,8 @@ uvc_function_set_alt(struct usb_function *f, unsigned
> interface, unsigned alt) v4l2_event_queue(uvc->vdev, &v4l2_event);
>
> uvc->state = UVC_STATE_CONNECTED;
> - break;
> +
No need for two blank lines here.
> + return 0;
>
> case 1:
> if (uvc->state != UVC_STATE_CONNECTED)
> @@ -352,14 +360,12 @@ uvc_function_set_alt(struct usb_function *f, unsigned
> interface, unsigned alt) v4l2_event.type = UVC_EVENT_STREAMON;
> v4l2_event_queue(uvc->vdev, &v4l2_event);
>
> - uvc->state = UVC_STATE_STREAMING;
> - break;
> +
Same here.
> + return USB_GADGET_DELAYED_STATUS;
>
> default:
> return -EINVAL;
> }
> -
> - return 0;
> }
>
> static void
> diff --git a/drivers/usb/gadget/uvc.h b/drivers/usb/gadget/uvc.h
> index 93b0c11..9391993 100644
> --- a/drivers/usb/gadget/uvc.h
> +++ b/drivers/usb/gadget/uvc.h
> @@ -190,6 +190,7 @@ struct uvc_file_handle
> * Functions
> */
>
> +extern void uvc_function_setup_continue(struct uvc_device *uvc);
> extern void uvc_endpoint_stream(struct uvc_device *dev);
>
> extern void uvc_function_connect(struct uvc_device *uvc);
> diff --git a/drivers/usb/gadget/uvc_v4l2.c b/drivers/usb/gadget/uvc_v4l2.c
> index 134bfe5..b47e0f7 100644
> --- a/drivers/usb/gadget/uvc_v4l2.c
> +++ b/drivers/usb/gadget/uvc_v4l2.c
> @@ -245,7 +245,20 @@ uvc_v4l2_do_ioctl(struct file *file, unsigned int cmd,
> void *arg) if (*type != video->queue.queue.type)
> return -EINVAL;
>
> - return uvc_video_enable(video, 1);
> + /* enable uvc video. */
Please start comments with a capital letter and spell UVC in uppercase.
> + ret = uvc_video_enable(video, 1);
> + if (ret < 0)
> + return ret;
> +
> + /*
> + * since the real video device has now started streaming
> + * its safe now to complete the status phase of the
> + * set_interface (alt setting 1)
> + */
I would change this comment, as not all use cases of the UVC gadget driver
involve a real video capture device. What about something like
"Complete the alternate setting selection setup phase now that userspace is
ready to provide video frames."
> + uvc_function_setup_continue(uvc);
> + uvc->state = UVC_STATE_STREAMING;
> +
> + return 0;
> }
>
> case VIDIOC_STREAMOFF:
--
Regards,
Laurent Pinchart
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