Hi Bhupesh, Thanks for the patch. We're almost there :-)
On Thursday 28 March 2013 10:39:13 Bhupesh Sharma wrote: > This patch reworks the videobuffer management logic present in the UVC > webcam gadget and ports it to use the "more apt" videobuf2 framework for > video buffer management. > > To support routing video data captured from a real V4L2 video capture > device with a "zero copy" operation on videobuffers (as they pass from > the V4L2 domain to UVC domain via a user-space application), we need to > support USER_PTR IO method at the UVC gadget side. > > So the V4L2 capture device driver can still continue to use MMAP IO > method and now the user-space application can just pass a pointer to the > video buffers being dequeued from the V4L2 device side while queueing > them at the UVC gadget end. This ensures that we have a "zero-copy" > design as the videobuffers pass from the V4L2 capture device to the UVC > gadget. > > Note that there will still be a need to apply UVC specific payload > headers on top of each UVC payload data, which will still require a copy > operation to be performed in the 'encode' routines of the UVC gadget. > > This patch also addresses one issue found out while porting the UVC > gadget to videobuf2 framework: > - In case the usb requests queued by the gadget get completed > with a status of -ESHUTDOWN (disconnected from host), > the queue of videobuf2 should be cancelled to ensure that the > application space daemon is not left in a state waiting for > a vb2 to be successfully absorbed at the USB side. > > Signed-off-by: Bhupesh Sharma <[email protected]> [snip] > diff --git a/drivers/usb/gadget/uvc_queue.c b/drivers/usb/gadget/uvc_queue.c > index 104ae9c..0d30171 100644 > --- a/drivers/usb/gadget/uvc_queue.c > +++ b/drivers/usb/gadget/uvc_queue.c [snip] > +static int uvc_queue_buffer(struct uvc_video_queue *queue, > + struct v4l2_buffer *buf) > +{ > + unsigned long flags; > + int ret; > > + mutex_lock(&queue->mutex); > spin_lock_irqsave(&queue->irqlock, flags); > + ret = vb2_qbuf(&queue->queue, buf); vb2_qbuf() must be called before spin_lock_irqsave(), as the uvc_buffer_queue() operation takes the same lock. The spin lock must thus protect the two lines below only. > ret = (queue->flags & UVC_QUEUE_PAUSED) != 0; > queue->flags &= ~UVC_QUEUE_PAUSED; > spin_unlock_irqrestore(&queue->irqlock, flags); > mutex_unlock(&queue->mutex); > > + return ret; > } -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
