media: videodev2: Add flag to unconditionally enumerate pixel formats

When the index is ORed with V4L2_FMTDESC_FLAG_ENUM_ALL the
driver clears the flag and enumerate all the possible formats,
ignoring any limitations from the current configuration.
Drivers which do not support this flag yet always return an EINVAL.

Signed-off-by: Benjamin Gaignard <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>
[hverkuil: improved doc when the new flag is not supported by the driver]

Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst

···
     * - __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 index is ORed with ``V4L2_FMTDESC_FLAG_ENUM_ALL`` the
+        driver clears the flag and enumerates all the possible formats,
+        ignoring any limitations from the current configuration. Drivers
+        which do not support this flag always return an ``EINVAL``
+        error code without clearing this flag.
+        Formats enumerated when using ``V4L2_FMTDESC_FLAG_ENUM_ALL`` flag
+        shouldn't be used when calling :c:func:`VIDIOC_ENUM_FRAMESIZES`
+        or :c:func:`VIDIOC_ENUM_FRAMEINTERVALS`.
+        ``V4L2_FMTDESC_FLAG_ENUM_ALL`` should only be used by drivers that
+        can return different format list depending on this flag.
     * - __u32
       - ``type``
       - Type of the data stream, set by the application. Only these types
···
 	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_FMTDESC_FLAG_ENUM_ALL``
+      - 0x80000000
+      - When the applications ORs ``index`` with ``V4L2_FMTDESC_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,
+        always return ``EINVAL`` without clearing this flag.
 
 Return Value
 ============

Documentation/userspace-api/media/videodev2.h.rst.exceptions

···
 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_FMTDESC_FLAG_ENUM_ALL fmtdesc-flags
 
 # V4L2 timecode types
 replace define V4L2_TC_TYPE_24FPS timecode-type

include/uapi/linux/videodev2.h

···
 #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_FMTDESC_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