From: Nas Chung nas.chung@chipsnmedia.com
[ Upstream commit f81f69a0e3da141bdd73a16b8676f4e542533d87 ]
V4L2_TYPE_IS_OUTPUT() returns true for V4L2_BUF_TYPE_VIDEO_OVERLAY which definitely belongs to CAPTURE.
Signed-off-by: Nas Chung nas.chung@chipsnmedia.com Signed-off-by: Sebastian Fricke sebastian.fricke@collabora.com Signed-off-by: Hans Verkuil hverkuil@xs4all.nl Signed-off-by: Sasha Levin sashal@kernel.org ---
**YES** This commit should be backported to stable kernel trees. **Detailed Analysis:** **1. Nature of the Bug:** The commit fixes a fundamental logic error in the `V4L2_TYPE_IS_OUTPUT` macro that has existed since 2012 (commit 607ca46e97a1b). The macro incorrectly classifies `V4L2_BUF_TYPE_VIDEO_OVERLAY` as an OUTPUT buffer type when it should be classified as a CAPTURE type. This is a clear logical bug in a core V4L2 API macro. **2. Code Impact Analysis:** The fix removes this line from the macro: ```c || (type) == V4L2_BUF_TYPE_VIDEO_OVERLAY ``` My investigation shows the macro is used in critical V4L2 core functions, particularly in: - **Crop/Selection handling** (`drivers/media/v4l2-core/v4l2-ioctl.c:2517, 2547, 2597`): The macro determines whether to use `V4L2_SEL_TGT_COMPOSE` (for output) vs `V4L2_SEL_TGT_CROP` (for capture) targets - **Parameter handling** (`drivers/media/v4l2-core/v4l2-ioctl.c:2269`): Affects how output vs capture parameters are processed - **Buffer management** in videobuf2 framework: Affects buffer direction logic **3. User Impact:** Applications using video overlay functionality have been subject to incorrect behavior where: - Overlay buffers were processed with output buffer logic instead of capture buffer logic - Wrong selection targets were used for crop operations on overlay devices - Parameter handling followed the wrong code paths **4. Risk Assessment:** - **Low regression risk**: The fix corrects clearly wrong behavior - there's no valid use case where VIDEO_OVERLAY should be treated as OUTPUT - **Contained scope**: Only affects the classification logic for one specific buffer type - **Clear correctness**: The fix aligns the code with the V4L2 specification and logical expectations **5. Comparison with Similar Commits:** Looking at the historical commits provided, while they show refactoring and API improvements that were not backported, this commit fixes a fundamental logical bug in core API behavior, which is different from cosmetic or enhancement changes. **6. Backport Suitability:** This meets all stable backport criteria: - ✅ Fixes a clear bug affecting users - ✅ Small, contained change with minimal risk - ✅ No new features or architectural changes - ✅ Affects core V4L2 functionality that could cause incorrect application behavior - ✅ Logic error that has persisted for over a decade The fix should be backported to ensure VIDEO_OVERLAY applications work correctly across all supported kernel versions.
include/uapi/linux/videodev2.h | 1 - 1 file changed, 1 deletion(-)
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h index 895c5ba8b6ac2..5384c9d61d510 100644 --- a/include/uapi/linux/videodev2.h +++ b/include/uapi/linux/videodev2.h @@ -164,7 +164,6 @@ enum v4l2_buf_type { #define V4L2_TYPE_IS_OUTPUT(type) \ ((type) == V4L2_BUF_TYPE_VIDEO_OUTPUT \ || (type) == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE \ - || (type) == V4L2_BUF_TYPE_VIDEO_OVERLAY \ || (type) == V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY \ || (type) == V4L2_BUF_TYPE_VBI_OUTPUT \ || (type) == V4L2_BUF_TYPE_SLICED_VBI_OUTPUT \