[RFC PATCH 2/2] media/uapi/v4l: clarify cropcap/crop/selection behavior

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From: Hans Verkuil <hans.verkuil@xxxxxxxxx>

Unfortunately the use of 'type' was inconsistent for multiplanar
buffer types. Starting with 4.12 both the normal and _MPLANE variants
are allowed, thus making it possible to write sensible code.

Yes, we messed up :-(

Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
---
 Documentation/media/uapi/v4l/vidioc-cropcap.rst    | 21 ++++++++++++---------
 Documentation/media/uapi/v4l/vidioc-g-crop.rst     | 22 +++++++++++++---------
 .../media/uapi/v4l/vidioc-g-selection.rst          | 22 ++++++++++++----------
 3 files changed, 37 insertions(+), 28 deletions(-)

diff --git a/Documentation/media/uapi/v4l/vidioc-cropcap.rst b/Documentation/media/uapi/v4l/vidioc-cropcap.rst
index f21a69b554e1..d354216846e6 100644
--- a/Documentation/media/uapi/v4l/vidioc-cropcap.rst
+++ b/Documentation/media/uapi/v4l/vidioc-cropcap.rst
@@ -39,16 +39,19 @@ structure. Drivers fill the rest of the structure. The results are
 constant except when switching the video standard. Remember this switch
 can occur implicit when switching the video input or output.
 
-Do not use the multiplanar buffer types. Use
-``V4L2_BUF_TYPE_VIDEO_CAPTURE`` instead of
-``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and use
-``V4L2_BUF_TYPE_VIDEO_OUTPUT`` instead of
-``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``.
-
 This ioctl must be implemented for video capture or output devices that
 support cropping and/or scaling and/or have non-square pixels, and for
 overlay devices.
 
+.. note::
+   Unfortunately in the case of multiplanar buffer types
+   (``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``)
+   this API was messed up with regards to how the :c:type:`v4l2_cropcap` ``type`` field
+   should be filled in. The Samsung Exynos drivers only accepted the
+   ``_MPLANE`` buffer type while other drivers only accepted a non-multiplanar
+   buffer type (i.e. without the ``_MPLANE`` at the end).
+
+   Starting with kernel 4.12 both variations are allowed.
 
 .. c:type:: v4l2_cropcap
 
@@ -62,9 +65,9 @@ overlay devices.
     * - __u32
       - ``type``
       - Type of the data stream, set by the application. Only these types
-	are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``,
-	``V4L2_BUF_TYPE_VIDEO_OUTPUT`` and
-	``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :c:type:`v4l2_buf_type`.
+	are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``, ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE``,
+	``V4L2_BUF_TYPE_VIDEO_OUTPUT``, ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE`` and
+	``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :c:type:`v4l2_buf_type` and the note above.
     * - struct :ref:`v4l2_rect <v4l2-rect-crop>`
       - ``bounds``
       - Defines the window within capturing or output is possible, this
diff --git a/Documentation/media/uapi/v4l/vidioc-g-crop.rst b/Documentation/media/uapi/v4l/vidioc-g-crop.rst
index 56a36340f565..8aabe33c8da7 100644
--- a/Documentation/media/uapi/v4l/vidioc-g-crop.rst
+++ b/Documentation/media/uapi/v4l/vidioc-g-crop.rst
@@ -45,12 +45,6 @@ and struct :c:type:`v4l2_rect` substructure named ``c`` of a
 v4l2_crop structure and call the :ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` ioctl with a pointer
 to this structure.
 
-Do not use the multiplanar buffer types. Use
-``V4L2_BUF_TYPE_VIDEO_CAPTURE`` instead of
-``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and use
-``V4L2_BUF_TYPE_VIDEO_OUTPUT`` instead of
-``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``.
-
 The driver first adjusts the requested dimensions against hardware
 limits, i. e. the bounds given by the capture/output window, and it
 rounds to the closest possible values of horizontal and vertical offset,
@@ -74,6 +68,16 @@ been negotiated.
 When cropping is not supported then no parameters are changed and
 :ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` returns the ``EINVAL`` error code.
 
+.. note::
+   Unfortunately in the case of multiplanar buffer types
+   (``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``)
+   this API was messed up with regards to how the :c:type:`v4l2_crop` ``type`` field
+   should be filled in. The Samsung Exynos drivers only accepted the
+   ``_MPLANE`` buffer type while other drivers only accepted a non-multiplanar
+   buffer type (i.e. without the ``_MPLANE`` at the end).
+
+   Starting with kernel 4.12 both variations are allowed.
+
 
 .. c:type:: v4l2_crop
 
@@ -87,9 +91,9 @@ When cropping is not supported then no parameters are changed and
     * - __u32
       - ``type``
       - Type of the data stream, set by the application. Only these types
-	are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``,
-	``V4L2_BUF_TYPE_VIDEO_OUTPUT`` and
-	``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :c:type:`v4l2_buf_type`.
+	are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``, ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE``,
+	``V4L2_BUF_TYPE_VIDEO_OUTPUT``, ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE`` and
+	``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :c:type:`v4l2_buf_type` and the note above.
     * - struct :c:type:`v4l2_rect`
       - ``c``
       - Cropping rectangle. The same co-ordinate system as for struct
diff --git a/Documentation/media/uapi/v4l/vidioc-g-selection.rst b/Documentation/media/uapi/v4l/vidioc-g-selection.rst
index deb1f6fb473b..8d4e7bf49eab 100644
--- a/Documentation/media/uapi/v4l/vidioc-g-selection.rst
+++ b/Documentation/media/uapi/v4l/vidioc-g-selection.rst
@@ -40,13 +40,19 @@ Description
 
 The ioctls are used to query and configure selection rectangles.
 
+.. note::
+   Unfortunately in the case of multiplanar buffer types
+   (``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``)
+   this API was messed up with regards to how the :c:type:`v4l2_selection` ``type`` field
+   should be filled in. The Samsung Exynos drivers only accepted the
+   ``_MPLANE`` buffer type while other drivers only accepted a non-multiplanar
+   buffer type (i.e. without the ``_MPLANE`` at the end).
+
+   Starting with kernel 4.12 both variations are allowed.
+
 To query the cropping (composing) rectangle set struct
 :c:type:`v4l2_selection` ``type`` field to the
-respective buffer type. Do not use the multiplanar buffer types. Use
-``V4L2_BUF_TYPE_VIDEO_CAPTURE`` instead of
-``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and use
-``V4L2_BUF_TYPE_VIDEO_OUTPUT`` instead of
-``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``. The next step is setting the
+respective buffer type. The next step is setting the
 value of struct :c:type:`v4l2_selection` ``target``
 field to ``V4L2_SEL_TGT_CROP`` (``V4L2_SEL_TGT_COMPOSE``). Please refer
 to table :ref:`v4l2-selections-common` or :ref:`selection-api` for
@@ -64,11 +70,7 @@ pixels.
 
 To change the cropping (composing) rectangle set the struct
 :c:type:`v4l2_selection` ``type`` field to the
-respective buffer type. Do not use multiplanar buffers. Use
-``V4L2_BUF_TYPE_VIDEO_CAPTURE`` instead of
-``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE``. Use
-``V4L2_BUF_TYPE_VIDEO_OUTPUT`` instead of
-``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``. The next step is setting the
+respective buffer type. The next step is setting the
 value of struct :c:type:`v4l2_selection` ``target`` to
 ``V4L2_SEL_TGT_CROP`` (``V4L2_SEL_TGT_COMPOSE``). Please refer to table
 :ref:`v4l2-selections-common` or :ref:`selection-api` for additional
-- 
2.11.0




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