Re: [PATCH v5 1/3] media: videodev2: Add flag to unconditionnaly enumerate pixels formats

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Le 30/07/2024 à 09:19, Hans Verkuil a écrit :
On 30/07/2024 09:08, Hans Verkuil wrote:
On 22/07/2024 17:05, Benjamin Gaignard wrote:
When the index field is ORed with V4L2_FMT_FLAG_ENUM_ALL the driver
will ignore any configuration and enumerate all the possible formats.
Drivers which do not support this flag yet always return an EINVAL
error code.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
---
changes in version 5:
- Reset the proposal to follow Hans's advices
- Add new flag to be used with index field.

  .../userspace-api/media/v4l/vidioc-enum-fmt.rst      | 12 +++++++++++-
  .../userspace-api/media/videodev2.h.rst.exceptions   |  1 +
  include/uapi/linux/videodev2.h                       |  3 +++
  3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
index 3adb3d205531..12e1e65e6a71 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
@@ -85,7 +85,11 @@ the ``mbus_code`` field is handled differently:
      * - __u32
        - ``index``
        - Number of the format in the enumeration, set by the application.
-	This is in no way related to the ``pixelformat`` field.
+        This is in no way related to the ``pixelformat`` field. When the
You need to start a new paragraph before 'When'. Otherwise you might read
that the 'When' sentence is somehow related to the previous sentence.

+        index is ORed with V4L2_FMT_FLAG_ENUM_ALL the driver will ignore
+        any configuration and enumerate all the possible formats. Drivers
I'd rephrase this a little bit:

the driver will enumerate all the possible formats, ignoring any limitations
from the current configuration.

And after that I would like to see an example of a use-case.
Should the flag be kept on return of VIDIOC_ENUM_FMT or should it be cleared?
For reference: VIDIOC_QUERYCTRL will clear the V4L2_CTRL_FLAG_NEXT_CTRL flag.

Regardless of what we pick, it should be documented.

I believe most of the flags are cleared in v4l2 so I will to do the same and
document it.


Regards,

	Hans

+        which do not support this flag yet always return an ``EINVAL``
+        error code.
      * - __u32
        - ``type``
        - Type of the data stream, set by the application. Only these types
@@ -234,6 +238,12 @@ the ``mbus_code`` field is handled differently:
  	valid. The buffer consists of ``height`` lines, each having ``width``
  	Data Units of data and the offset (in bytes) between the beginning of
  	each two consecutive lines is ``bytesperline``.
+    * - ``V4L2_FMT_FLAG_ENUM_ALL``
I am not really happy with this name since the prefix is identical to that
of other V4L2_FMT_FLAG_ defines. How about: V4L2_FMTDESC_FLAG_ENUM_ALL?
Or V4L2_FMT_IDX_ENUM_ALL?

+      - 0x80000000
+      - When the applications ORs ``index`` with ``V4L2_FMT_FLAG_ENUM_ALL`` flag
+        the driver enumerates all the possible pixel formats without taking care
+        of any already set configuration. Drivers which do not support this flag
+        yet always return ``EINVAL``.
Return Value
  ============
diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
index bdc628e8c1d6..8dc10a500fc6 100644
--- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
+++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
@@ -216,6 +216,7 @@ replace define V4L2_FMT_FLAG_CSC_YCBCR_ENC fmtdesc-flags
  replace define V4L2_FMT_FLAG_CSC_HSV_ENC fmtdesc-flags
  replace define V4L2_FMT_FLAG_CSC_QUANTIZATION fmtdesc-flags
  replace define V4L2_FMT_FLAG_META_LINE_BASED fmtdesc-flags
+replace define V4L2_FMT_FLAG_ENUM_ALL fmtdesc-flags
# V4L2 timecode types
  replace define V4L2_TC_TYPE_24FPS timecode-type
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 4e91362da6da..3d11f91273a1 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -904,6 +904,9 @@ struct v4l2_fmtdesc {
  #define V4L2_FMT_FLAG_CSC_QUANTIZATION		0x0100
  #define V4L2_FMT_FLAG_META_LINE_BASED		0x0200
+/* Format description flag, to be ORed with the index */
+#define V4L2_FMT_FLAG_ENUM_ALL			0x80000000
+
  	/* Frame Size and frame rate enumeration */
  /*
   *	F R A M E   S I Z E   E N U M E R A T I O N
Regards,

	Hans






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