[media] v4l2: uvcvideo: Allow using larger buffers

A test in uvc_video_decode_isoc() checks whether an image has been
received from the camera completely. For this the data amount is compared
to the buffer length, which, however, doesn't have to be equal to the
image size. Switch to using formats .sizeimage field for an exact
expected image size.

[Renamed image_size to frame_size]

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/usb/uvc/uvc_v4l2.c

@@ -318,6 +318,7 @@ static int uvc_v4l2_set_format(struct uvc_streaming *stream,
 	stream->ctrl = probe;
 	stream->cur_format = format;
 	stream->cur_frame = frame;
+	stream->frame_size = fmt->fmt.pix.sizeimage;
 
 done:
 	mutex_unlock(&stream->mutex);

drivers/media/usb/uvc/uvc_video.c

@@ -1143,7 +1143,7 @@ static int uvc_video_encode_data(struct uvc_streaming *stream,
 static void uvc_video_validate_buffer(const struct uvc_streaming *stream,
 				      struct uvc_buffer *buf)
 {
-	if (buf->length != buf->bytesused &&
+	if (stream->frame_size != buf->bytesused &&
 	    !(stream->cur_format->flags & UVC_FMT_FLAG_COMPRESSED))
 		buf->error = 1;
 }

drivers/media/usb/uvc/uvcvideo.h

@@ -457,6 +457,8 @@ struct uvc_streaming {
 	struct uvc_format *def_format;
 	struct uvc_format *cur_format;
 	struct uvc_frame *cur_frame;
+	size_t frame_size;
+
 	/* Protect access to ctrl, cur_format, cur_frame and hardware video
 	 * probe control.
 	 */