It has been decided to use the ENUM_FMT index value as a hint for driver preference. This is defined purposedly in a very liberal way, letting drivers define what "preference" means. For instance, the Hantro VPU driver indicates additional processing to output a given format, and thus implicates more CPU usage, which is enumerated after native (non-processed) formats. Signed-off-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx> Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> --- Documentation/media/uapi/v4l/vidioc-enum-fmt.rst | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst index 399ef1062bac..8ca6ab701e4a 100644 --- a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst +++ b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst @@ -44,7 +44,9 @@ To enumerate image formats applications initialize the ``type`` and the :ref:`VIDIOC_ENUM_FMT` ioctl with a pointer to this structure. Drivers fill the rest of the structure or return an ``EINVAL`` error code. All formats are enumerable by beginning at index zero and incrementing by -one until ``EINVAL`` is returned. +one until ``EINVAL`` is returned. If applicable, drivers shall return +formats in preference order, where preferred formats are returned before +(that is, with lower ``index`` value) less-preferred formats. .. note:: -- 2.22.0
