[PATCHv3 1/2] doc/media api: Try to make enum usage clearer

[PATCHv3 1/2] doc/media api: Try to make enum usage clearer

[Dorota Czaplejewicz]

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This clarifies which side of the calls is responsible for doing what to which parts of the struct.
This also explicitly states that repeating values are disallowed.
It also expands the terse description of the access algorithm into more prose-like, active voice description, which trades conciseness for ease of comprehension.

Added: mbus codes must not repeat
Added: no holes in the enumeration
Added: enumerations per what?
Added: who fills in what in calls
Changed: "zero" -> "0"
Changed: "given" -> "specified"

Still unclear how it works so didn't describe: "which". What is a "try format" vs "active format"?

Signed-off-by: Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm>
---
Hi,

I took those patches out of the freezer. I made sure they still apply (they do), and corrected some errors pointed out by Jacopo in the previous round of reviews.

Thanks,
Dorota

 .../v4l/vidioc-subdev-enum-mbus-code.rst      | 38 +++++++++++++------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-mbus-code.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-mbus-code.rst
index 417f1a19bcc4..63bff24d0520 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-mbus-code.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-mbus-code.rst
@@ -31,15 +31,28 @@ Arguments
 Description
 ===========
 
-To enumerate media bus formats available at a given sub-device pad
-applications initialize the ``pad``, ``which`` and ``index`` fields of
-struct
-:c:type:`v4l2_subdev_mbus_code_enum` and
-call the :ref:`VIDIOC_SUBDEV_ENUM_MBUS_CODE` ioctl with a pointer to this
-structure. Drivers fill the rest of the structure or return an ``EINVAL``
-error code if either the ``pad`` or ``index`` are invalid. All media bus
-formats are enumerable by beginning at index zero and incrementing by
-one until ``EINVAL`` is returned.
+This call is used by the application to access the enumeration
+of media bus formats for the selected pad.
+
+The enumerations are defined by the driver, and indexed using the ``index`` field
+of struct :c:type:`v4l2_subdev_mbus_code_enum`.
+Each enumeration starts with the ``index`` of 0, and
+the lowest invalid index marks the end of enumeration.
+
+Therefore, to enumerate media bus formats available at a given sub-device pad,
+initialize the ``pad``, and ``which`` fields to desired values,
+and set ``index`` to 0.
+Then call the :ref:`VIDIOC_SUBDEV_ENUM_MBUS_CODE` ioctl
+with a pointer to this structure.
+
+A successful call will return with the ``code`` field filled in
+with a mbus code value.
+Repeat with increasing ``index`` until ``EINVAL`` is received.
+``EINVAL`` means that either ``pad`` is invalid,
+or that there are no more codes available at this pad.
+
+The driver must not return the same value of ``code`` for different indices
+at the same pad.
 
 Available media bus formats may depend on the current 'try' formats at
 other pads of the sub-device, as well as on the current active links.
@@ -57,14 +70,15 @@ information about the try formats.
 
     * - __u32
       - ``pad``
-      - Pad number as reported by the media controller API.
+      - Pad number as reported by the media controller API. Filled in by the application.
     * - __u32
       - ``index``
-      - Number of the format in the enumeration, set by the application.
+      - Index of the mbus code in the enumeration belonging to the given pad.
+    Filled in by the application.
     * - __u32
       - ``code``
       - The media bus format code, as defined in
-	:ref:`v4l2-mbus-format`.
+	:ref:`v4l2-mbus-format`. Filled in by the driver.
     * - __u32
       - ``which``
       - Media bus format codes to be enumerated, from enum
-- 
2.38.1


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[PATCHv3 2/2] media api: Try to make enum usage clearer

[Dorota Czaplejewicz]

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This clarifies which side of the calls is responsible for doing what to which parts of the struct.
It also expands the terse description of the access algorithm into more prose-like, active voice description, which trades conciseness for ease of comprehension.

Fixed: typo "format" -> "frame size" in enum-frame-size
Added: no holes in the enumeration
Added: enumerations per what?
Added: who fills in what in calls
Changed: "given" -> "specified"

Signed-off-by: Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm>
---
 .../v4l/vidioc-subdev-enum-frame-size.rst     | 44 ++++++++++++-------
 1 file changed, 29 insertions(+), 15 deletions(-)

diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst
index c25a9896df0e..82b5d2538fa9 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst
@@ -31,18 +31,30 @@ Arguments
 Description
 ===========
 
-This ioctl allows applications to enumerate all frame sizes supported by
-a sub-device on the given pad for the given media bus format. Supported
-formats can be retrieved with the
+This ioctl allows applications to access the enumeration of frame sizes
+supported by a sub-device on the specified pad
+for the specified media bus format.
+Supported formats can be retrieved with the
 :ref:`VIDIOC_SUBDEV_ENUM_MBUS_CODE`
 ioctl.
 
-To enumerate frame sizes applications initialize the ``pad``, ``which``
-, ``code`` and ``index`` fields of the struct
-:c:type:`v4l2_subdev_mbus_code_enum` and
-call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_SIZE` ioctl with a pointer to the
-structure. Drivers fill the minimum and maximum frame sizes or return an
-EINVAL error code if one of the input parameters is invalid.
+The enumerations are defined by the driver, and indexed using the ``index`` field
+of the struct :c:type:`v4l2_subdev_mbus_code_enum`.
+Each pair of ``pad`` and ``code`` correspond to a separate enumeration.
+Each enumeration starts with the ``index`` of 0, and
+the lowest invalid index marks the end of the enumeration.
+
+Therefore, to enumerate frame sizes allowed on the specified pad
+and using the specified mbus format, initialize the
+``pad``, ``which``, and ``code`` fields to desired values,
+and set ``index`` to 0.
+Then call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_SIZE` ioctl with a pointer to the
+structure.
+
+A successful call will return with minimum and maximum frame sizes filled in.
+Repeat with increasing ``index`` until ``EINVAL`` is received.
+``EINVAL`` means that either no more entries are available in the enumeration,
+or that an input parameter was invalid.
 
 Sub-devices that only support discrete frame sizes (such as most
 sensors) will return one or more frame sizes with identical minimum and
@@ -72,26 +84,28 @@ information about try formats.
 
     * - __u32
       - ``index``
-      - Number of the format in the enumeration, set by the application.
+      - Index of the frame size in the enumeration belonging to the given pad and format.
+	Filled in by the application.
     * - __u32
       - ``pad``
       - Pad number as reported by the media controller API.
+	Filled in by the application.
     * - __u32
       - ``code``
       - The media bus format code, as defined in
-	:ref:`v4l2-mbus-format`.
+	:ref:`v4l2-mbus-format`. Filled in by the application.
     * - __u32
       - ``min_width``
-      - Minimum frame width, in pixels.
+      - Minimum frame width, in pixels. Filled in by the driver.
     * - __u32
       - ``max_width``
-      - Maximum frame width, in pixels.
+      - Maximum frame width, in pixels. Filled in by the driver.
     * - __u32
       - ``min_height``
-      - Minimum frame height, in pixels.
+      - Minimum frame height, in pixels. Filled in by the driver.
     * - __u32
       - ``max_height``
-      - Maximum frame height, in pixels.
+      - Maximum frame height, in pixels. Filled in by the driver.
     * - __u32
       - ``which``
       - Frame sizes to be enumerated, from enum
-- 
2.38.1


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[PATCHv3 2/2 RESEND] media api: Try to make enum usage clearer

[Dorota Czaplejewicz]

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This clarifies which side of the calls is responsible for doing what to which parts of the struct.
It also expands the terse description of the access algorithm into more prose-like, active voice description, which trades conciseness for ease of comprehension.

Fixed: typo "format" -> "frame size" in enum-frame-size
Added: no holes in the enumeration
Added: enumerations per what?
Added: who fills in what in calls
Changed: "given" -> "specified"

Signed-off-by: Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm>
---
 .../v4l/vidioc-subdev-enum-frame-size.rst     | 44 ++++++++++++-------
 1 file changed, 29 insertions(+), 15 deletions(-)

diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst
index c25a9896df0e..82b5d2538fa9 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst
@@ -31,18 +31,30 @@ Arguments
 Description
 ===========
 
-This ioctl allows applications to enumerate all frame sizes supported by
-a sub-device on the given pad for the given media bus format. Supported
-formats can be retrieved with the
+This ioctl allows applications to access the enumeration of frame sizes
+supported by a sub-device on the specified pad
+for the specified media bus format.
+Supported formats can be retrieved with the
 :ref:`VIDIOC_SUBDEV_ENUM_MBUS_CODE`
 ioctl.
 
-To enumerate frame sizes applications initialize the ``pad``, ``which``
-, ``code`` and ``index`` fields of the struct
-:c:type:`v4l2_subdev_mbus_code_enum` and
-call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_SIZE` ioctl with a pointer to the
-structure. Drivers fill the minimum and maximum frame sizes or return an
-EINVAL error code if one of the input parameters is invalid.
+The enumerations are defined by the driver, and indexed using the ``index`` field
+of the struct :c:type:`v4l2_subdev_mbus_code_enum`.
+Each pair of ``pad`` and ``code`` correspond to a separate enumeration.
+Each enumeration starts with the ``index`` of 0, and
+the lowest invalid index marks the end of the enumeration.
+
+Therefore, to enumerate frame sizes allowed on the specified pad
+and using the specified mbus format, initialize the
+``pad``, ``which``, and ``code`` fields to desired values,
+and set ``index`` to 0.
+Then call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_SIZE` ioctl with a pointer to the
+structure.
+
+A successful call will return with minimum and maximum frame sizes filled in.
+Repeat with increasing ``index`` until ``EINVAL`` is received.
+``EINVAL`` means that either no more entries are available in the enumeration,
+or that an input parameter was invalid.
 
 Sub-devices that only support discrete frame sizes (such as most
 sensors) will return one or more frame sizes with identical minimum and
@@ -72,26 +84,28 @@ information about try formats.
 
     * - __u32
       - ``index``
-      - Number of the format in the enumeration, set by the application.
+      - Index of the frame size in the enumeration belonging to the given pad and format.
+	Filled in by the application.
     * - __u32
       - ``pad``
       - Pad number as reported by the media controller API.
+	Filled in by the application.
     * - __u32
       - ``code``
       - The media bus format code, as defined in
-	:ref:`v4l2-mbus-format`.
+	:ref:`v4l2-mbus-format`. Filled in by the application.
     * - __u32
       - ``min_width``
-      - Minimum frame width, in pixels.
+      - Minimum frame width, in pixels. Filled in by the driver.
     * - __u32
       - ``max_width``
-      - Maximum frame width, in pixels.
+      - Maximum frame width, in pixels. Filled in by the driver.
     * - __u32
       - ``min_height``
-      - Minimum frame height, in pixels.
+      - Minimum frame height, in pixels. Filled in by the driver.
     * - __u32
       - ``max_height``
-      - Maximum frame height, in pixels.
+      - Maximum frame height, in pixels. Filled in by the driver.
     * - __u32
       - ``which``
       - Frame sizes to be enumerated, from enum
-- 
2.38.1


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