[v3,3/3] media: vidioc-enum-fmt.rst: clarify format preference
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Message ID 20191113175603.24742-4-ezequiel@collabora.com
State New
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Series
  • Enable Hantro G1 post-processor
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Commit Message

Ezequiel Garcia Nov. 13, 2019, 5:56 p.m. UTC
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@collabora.com>
---
 Documentation/media/uapi/v4l/vidioc-enum-fmt.rst | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Boris Brezillon Nov. 14, 2019, 9:32 a.m. UTC | #1
On Wed, 13 Nov 2019 14:56:03 -0300
Ezequiel Garcia <ezequiel@collabora.com> wrote:

> 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@collabora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

> ---
>  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::
>

Patch
diff mbox series

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::