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SubjectRe: [PATCH 2/5] media: docs: clarify relationship between crop and selection APIs
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On 04/03/2018 11:15 PM, Luca Ceresoli wrote:
> Having two somewhat similar and largely overlapping APIs is confusing,
> especially since the older one appears in the docs before the newer
> and most featureful counterpart.
>
> Clarify all of this in several ways:
> - swap the two sections
> - give a name to the two APIs in the section names
> - add a note at the beginning of the CROP API section
>
> Also remove a note that is incorrect (correct wording is in
> vidioc-cropcap.rst).
>
> Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
> Based on info from: Hans Verkuil <hverkuil@xs4all.nl>
> Cc: Hans Verkuil <hverkuil@xs4all.nl>
> ---
> Documentation/media/uapi/v4l/common.rst | 2 +-
> Documentation/media/uapi/v4l/crop.rst | 21 ++++++++++++---------
> Documentation/media/uapi/v4l/selection-api-005.rst | 2 ++
> Documentation/media/uapi/v4l/selection-api.rst | 4 ++--
> 4 files changed, 17 insertions(+), 12 deletions(-)
>
> diff --git a/Documentation/media/uapi/v4l/common.rst b/Documentation/media/uapi/v4l/common.rst
> index 13f2ed3fc5a6..5f93e71122ef 100644
> --- a/Documentation/media/uapi/v4l/common.rst
> +++ b/Documentation/media/uapi/v4l/common.rst
> @@ -41,6 +41,6 @@ applicable to all devices.
> extended-controls
> format
> planar-apis
> - crop
> selection-api
> + crop
> streaming-par
> diff --git a/Documentation/media/uapi/v4l/crop.rst b/Documentation/media/uapi/v4l/crop.rst
> index 182565b9ace4..83fa16eb347e 100644
> --- a/Documentation/media/uapi/v4l/crop.rst
> +++ b/Documentation/media/uapi/v4l/crop.rst
> @@ -2,9 +2,18 @@
>
> .. _crop:
>
> -*************************************
> -Image Cropping, Insertion and Scaling
> -*************************************
> +*****************************************************
> +Image Cropping, Insertion and Scaling -- the CROP API
> +*****************************************************
> +
> +.. note::
> +
> + The CROP API is mostly superseded by the newer :ref:`SELECTION API
> + <selection-api>`. The new API should be preferred in most cases,
> + with the exception of pixel aspect ratio detection, which is
> + implemented by :ref:`VIDIOC_CROPCAP <VIDIOC_CROPCAP>` and has no
> + equivalent in the SELECTION API. See :ref:`selection-vs-crop` for a
> + comparison of the two APIs.
>
> Some video capture devices can sample a subsection of the picture and
> shrink or enlarge it to an image of arbitrary size. We call these
> @@ -40,12 +49,6 @@ support scaling or the :ref:`VIDIOC_G_CROP <VIDIOC_G_CROP>` and
> :ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` ioctls. Their size (and position
> where applicable) will be fixed in this case.
>
> -.. note::
> -
> - All capture and output devices must support the
> - :ref:`VIDIOC_CROPCAP <VIDIOC_CROPCAP>` ioctl such that applications
> - can determine if scaling takes place.

This note should be rewritten, not deleted:

All capture and output devices that support the CROP or SELECTION API
will also support the :ref:`VIDIOC_CROPCAP <VIDIOC_CROPCAP>` ioctl.

Regards,

Hans

> -
>
> Cropping Structures
> ===================
> diff --git a/Documentation/media/uapi/v4l/selection-api-005.rst b/Documentation/media/uapi/v4l/selection-api-005.rst
> index 5b47a28ac6d7..2ad30a49184f 100644
> --- a/Documentation/media/uapi/v4l/selection-api-005.rst
> +++ b/Documentation/media/uapi/v4l/selection-api-005.rst
> @@ -1,5 +1,7 @@
> .. -*- coding: utf-8; mode: rst -*-
>
> +.. _selection-vs-crop:
> +
> ********************************
> Comparison with old cropping API
> ********************************
> diff --git a/Documentation/media/uapi/v4l/selection-api.rst b/Documentation/media/uapi/v4l/selection-api.rst
> index 81ea52d785b9..e4e623824b30 100644
> --- a/Documentation/media/uapi/v4l/selection-api.rst
> +++ b/Documentation/media/uapi/v4l/selection-api.rst
> @@ -2,8 +2,8 @@
>
> .. _selection-api:
>
> -API for cropping, composing and scaling
> -=======================================
> +Cropping, composing and scaling -- the SELECTION API
> +====================================================
>
>
> .. toctree::
>

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