libcamera: framebuffer: Add assertion to detect offset is unfilled

The offset variable is introduced to FrameBuffer::Plane. In order to
detect that the plane is used while the offset is not set, this adds
the assertion to FrameBuffer::planes(). It should be removed in the
future.

Signed-off-by: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/libcamera/framebuffer.cpp

@@ -170,6 +170,11 @@ FrameBuffer::Private::Private()
  * multiple dmabufs, based on the camera requirements.
  */
 
+/**
+ * \var FrameBuffer::Plane::kInvalidOffset
+ * \brief Invalid offset value, to identify uninitialized planes
+ */
+
 /**
  * \var FrameBuffer::Plane::fd
  * \brief The dmabuf file descriptor