[libcamera-devel] [PATCH v4 6/8] libcamera: v4l2_videodevice: Do not allow buffer queueing in stopping state

[Naushir Patuck]

If the device is in the process of being stopped (i.e. Stopping state), any
call to queueBuffer() must fail. This is to ensure the integrity of the buffer
queue, as it gets cleared at the end of streamOff.

Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
---
 src/libcamera/v4l2_videodevice.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
index 9cea6a608660..1516be129d73 100644
--- a/src/libcamera/v4l2_videodevice.cpp
+++ b/src/libcamera/v4l2_videodevice.cpp
@@ -1491,6 +1491,9 @@ int V4L2VideoDevice::releaseBuffers()
  * The best available V4L2 buffer is picked for \a buffer using the V4L2 buffer
  * cache.
  *
+ * Note that \a queueBuffer will fail if the device is in the process of being
+ * stopped from a streaming state through the \a streamOff function.
+ *
  * \return 0 on success or a negative error code otherwise
  */
 int V4L2VideoDevice::queueBuffer(FrameBuffer *buffer)
@@ -1499,6 +1502,11 @@ int V4L2VideoDevice::queueBuffer(FrameBuffer *buffer)
 	struct v4l2_buffer buf = {};
 	int ret;
 
+	if (state_ == State::Stopping) {
+		LOG(V4L2, Error) << "Device is in a stopping state.";
+		return -EPERM;
+	}
+
 	/*
 	 * Pipeline handlers should not requeue buffers after releasing the
 	 * buffers on the device. Any occurence of this error should be fixed
-- 
2.25.1