libcamera: buffer: Add buffer completion status

Add a new field to the Buffer class to report its completion status,
with a new cancel() method to mark the buffer as cancelled.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/libcamera/v4l2_device.cpp

@@ -799,6 +799,8 @@ Buffer *V4L2Device::dequeueBuffer()
 	buffer->timestamp_ = buf.timestamp.tv_sec * 1000000000ULL
 			   + buf.timestamp.tv_usec * 1000ULL;
 	buffer->sequence_ = buf.sequence;
+	buffer->status_ = buf.flags & V4L2_BUF_FLAG_ERROR
+			? Buffer::BufferError : Buffer::BufferSuccess;
 
 	return buffer;
 }