[PATCH v1] [media] uvcvideo: mark buffer error where overflow

[PATCH v1] [media] uvcvideo: mark buffer error where overflow

[Baoyou Xie]

Some cameras post inaccurate frame where next frame data overlap
it. this results in screen flicker, and it need to be prevented.

So this patch marks the buffer error to discard the frame where
buffer overflow.

Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org>
---
 drivers/media/usb/uvc/uvc_video.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index fb86d6a..81a3530 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -1077,6 +1077,7 @@ static void uvc_video_decode_data(struct uvc_streaming *stream,
 	/* Complete the current frame if the buffer size was exceeded. */
 	if (len > maxlen) {
 		uvc_trace(UVC_TRACE_FRAME, "Frame complete (overflow).\n");
+		buf->error = 1;
 		buf->state = UVC_BUF_STATE_READY;
 	}
 }
-- 
2.7.4

Re: [PATCH v1] [media] uvcvideo: mark buffer error where overflow

[Laurent Pinchart]

Hi Baoyou,

Thank you for the patch.

On Thursday, 7 September 2017 05:59:48 EEST Baoyou Xie wrote:
> Some cameras post inaccurate frame where next frame data overlap
> it. this results in screen flicker, and it need to be prevented.
> 
> So this patch marks the buffer error to discard the frame where
> buffer overflow.

I've thought about this before and I wasn't sure how to handle this case. As 
such an overflow might not signal an erroneous buffer, as the buffer could 
contain a valid image. However, if you have seen erroneous buffer contents in 
this case, and given that overflows should not occur, I think we could decide 
to stay on the safe side and set the error flag.

> Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org>

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

I'll apply the patch to my tree.

> ---
>  drivers/media/usb/uvc/uvc_video.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/media/usb/uvc/uvc_video.c
> b/drivers/media/usb/uvc/uvc_video.c index fb86d6a..81a3530 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -1077,6 +1077,7 @@ static void uvc_video_decode_data(struct uvc_streaming
> *stream, /* Complete the current frame if the buffer size was exceeded. */
> if (len > maxlen) {
>  		uvc_trace(UVC_TRACE_FRAME, "Frame complete (overflow).\n");
> +		buf->error = 1;
>  		buf->state = UVC_BUF_STATE_READY;
>  	}
>  }


-- 
Regards,

Laurent Pinchart

[PATCH v1] [media] uvcvideo: mark buffer error where overflow

[Baoyou Xie]

Some cameras post inaccurate frame where next frame data overlap
it. this results in screen flicker, and it need to be prevented.

So this patch marks the buffer error to discard the frame where
buffer overflow.

Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org>
---
 drivers/media/usb/uvc/uvc_video.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index fb86d6a..81a3530 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -1077,6 +1077,7 @@ static void uvc_video_decode_data(struct uvc_streaming *stream,
 	/* Complete the current frame if the buffer size was exceeded. */
 	if (len > maxlen) {
 		uvc_trace(UVC_TRACE_FRAME, "Frame complete (overflow).\n");
+		buf->error = 1;
 		buf->state = UVC_BUF_STATE_READY;
 	}
 }
-- 
2.7.4