Hi Bhupesh,
Thanks for the patch, and sorry for the late reply.
On Friday 01 June 2012 15:08:58 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.
That sounds good, thank you for coming up with a solution to this issue.
> 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. Also, we need
> to enable UVC video related stuff at the first QBUF ioctl call itself, as
> the application will call the STREAMON on UVC side only when it has
> dequeued sufficient buffers from the V4L2 side and queued them to the UVC
> gadget. So, the UVC video enable stuff cannot be done in STREAMON ioctl
> call.
Is that really required ? First of all, the userspace application can queue
buffers before it calls VIDIOC_STREAMON. Assuming it doesn't, the gadget
driver calls uvc_video_enable() at streamon time, which then calls
uvc_video_pump(). As no buffer is queued, the function will return without
queuing any USB request, so we shouldn't have any problem.
> For the same we add two more UVC states:
> - PRE_STREAMING : not even a single buffer has been queued to UVC
> - BUF_QUEUED_STREAMING_OFF : one video buffer has been queued to UVC
> but we have not yet enabled STREAMING on UVC side.
>
> Signed-off-by: Bhupesh Sharma <bhupesh.sharma@xxxxxx>
> ---
> drivers/usb/gadget/f_uvc.c | 17 ++++++++++++-----
> drivers/usb/gadget/uvc.h | 3 +++
> drivers/usb/gadget/uvc_v4l2.c | 38 ++++++++++++++++++++++++++++++++++++--
> 3 files changed, 51 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/usb/gadget/f_uvc.c b/drivers/usb/gadget/f_uvc.c
> index 2a8bf06..3589ed0 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;
> +
> + return 0;
>
> case 1:
> if (uvc->state != UVC_STATE_CONNECTED)
> @@ -352,14 +360,13 @@ 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;
> + uvc->state = UVC_STATE_PRE_STREAMING;
> +
> + 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 d78ea25..6cd1435 100644
> --- a/drivers/usb/gadget/uvc.h
> +++ b/drivers/usb/gadget/uvc.h
> @@ -141,6 +141,8 @@ enum uvc_state
> {
> UVC_STATE_DISCONNECTED,
> UVC_STATE_CONNECTED,
> + UVC_STATE_PRE_STREAMING,
> + UVC_STATE_BUF_QUEUED_STREAMING_OFF,
> UVC_STATE_STREAMING,
> };
>
> @@ -190,6 +192,7 @@ 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 9c2b45b..5f23571 100644
> --- a/drivers/usb/gadget/uvc_v4l2.c
> +++ b/drivers/usb/gadget/uvc_v4l2.c
> @@ -235,10 +235,36 @@ uvc_v4l2_do_ioctl(struct file *file, unsigned int cmd,
> void *arg) }
>
> case VIDIOC_QBUF:
> + /*
> + * Theory of operation:
> + * - for the very first QBUF call the uvc state will be
> + * UVC_STATE_PRE_STREAMING, so we need to initialize
> + * the UVC video pipe (allocate requests, init queue,
> + * ..) and change the uvc state to
> + * UVC_STATE_BUF_QUEUED_STREAMING_OFF.
> + *
> + * - For the QBUF calls thereafter, (until STREAMON is
> + * called) we just need to queue the buffers.
> + *
> + * - Once STREAMON has been called (which is handled by the
> + * STREAMON case below), we need to start pumping the data
> + * to USB side here itself.
> + */
> if ((ret = uvc_queue_buffer(&video->queue, arg)) < 0)
> return ret;
>
> - return uvc_video_pump(video);
> + if (uvc->state == UVC_STATE_PRE_STREAMING) {
> + ret = uvc_video_enable(video, 1);
> + if (ret < 0)
> + return ret;
> +
> + uvc->state = UVC_STATE_BUF_QUEUED_STREAMING_OFF;
> + return 0;
> + } else if (uvc->state == UVC_STATE_STREAMING) {
> + return uvc_video_pump(video);
> + } else {
> + return 0;
> + }
>
> case VIDIOC_DQBUF:
> return uvc_dequeue_buffer(&video->queue, arg,
> @@ -251,7 +277,15 @@ 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);
> + /*
> + * since the real video device has now started streaming
> + * its safe now to complete the status phase of the
> + * set_interface (alt setting 1)
> + */
> + uvc_function_setup_continue(uvc);
> + uvc->state = UVC_STATE_STREAMING;
> +
> + return 0;
> }
>
> case VIDIOC_STREAMOFF:
--
Regards,
Laurent Pinchart
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