On Mon Jul 20 18:17:26 2026 +0900, Ming Qian wrote:
> SMPTE ST 2086 defines the nominal ranges for mastering display
> chromaticity and luminance values. Its Annex A also documents that
> CTA 861-G uses zero maximum and minimum luminance values to signal
> that the corresponding values are unknown, and the xy chromaticity
> coordinate (0, 0) to signal that the white point chromaticity is
> unknown.
>
> The V4L2 HDR10 mastering display compound control currently rejects
> these values. Consequently, an unknown white point or luminance value
> prevents the entire compound control from being updated, making the
> other valid mastering display metadata unavailable to userspace.
>
> Accept (0, 0) as an unknown white point and zero as an unknown maximum
> or minimum mastering luminance. Continue to reject partially zero white
> point coordinates and non-zero values outside the nominal ranges.
> Display primary validation remains unchanged.
>
> Document the newly accepted unknown values in the V4L2 userspace API.
>
> Fixes: 1ad0de78e794 ("media: v4l: Add HDR10 static metadata controls")
> Cc: [email protected]
> Signed-off-by: Ming Qian <[email protected]>
> Signed-off-by: Hans Verkuil <[email protected]>
Patch committed.
Thanks,
Hans Verkuil
.../media/v4l/ext-ctrls-colorimetry.rst | 12 ++++-
drivers/media/v4l2-core/v4l2-ctrls-core.c | 53 ++++++++++++++--------
2 files changed, 46 insertions(+), 19 deletions(-)
---
diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-colorimetry.rst
b/Documentation/userspace-api/media/v4l/ext-ctrls-colorimetry.rst
index 38a4136d7220..0a7da2f16850 100644
--- a/Documentation/userspace-api/media/v4l/ext-ctrls-colorimetry.rst
+++ b/Documentation/userspace-api/media/v4l/ext-ctrls-colorimetry.rst
@@ -80,15 +80,25 @@ Colorimetry Control IDs
- ``white_point_x``
- Specifies the normalized x chromaticity coordinate of the white
point of the mastering display in increments of 0.00002.
+ When both ``white_point_x`` and ``white_point_y`` are zero,
+ the white point chromaticity is unknown. If either coordinate is
+ non-zero, both coordinates shall be within their valid ranges.
* - __u16
- ``white_point_y``
- Specifies the normalized y chromaticity coordinate of the white
point of the mastering display in increments of 0.00002.
+ When both ``white_point_x`` and ``white_point_y`` are zero,
+ the white point chromaticity is unknown. If either coordinate is
+ non-zero, both coordinates shall be within their valid ranges.
* - __u32
- ``max_luminance``
- Specifies the nominal maximum display luminance of the mastering
display in units of 0.0001 cd/m\ :sup:`2`.
+ A value of zero indicates that the nominal maximum display
+ luminance is unknown.
* - __u32
- ``min_luminance``
- - specifies the nominal minimum display luminance of the mastering
+ - Specifies the nominal minimum display luminance of the mastering
display in units of 0.0001 cd/m\ :sup:`2`.
+ A value of zero indicates that the nominal minimum display
+ luminance is unknown.
diff --git a/drivers/media/v4l2-core/v4l2-ctrls-core.c
b/drivers/media/v4l2-core/v4l2-ctrls-core.c
index 1214e7744ac0..5b8a594fb9e2 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-core.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-core.c
@@ -1322,24 +1322,41 @@ static int std_validate_compound(const struct v4l2_ctrl
*ctrl, u32 idx,
return -EINVAL;
}
- if (p_hdr10_mastering->white_point_x <
- V4L2_HDR10_MASTERING_WHITE_POINT_X_LOW ||
- p_hdr10_mastering->white_point_x >
- V4L2_HDR10_MASTERING_WHITE_POINT_X_HIGH ||
- p_hdr10_mastering->white_point_y <
- V4L2_HDR10_MASTERING_WHITE_POINT_Y_LOW ||
- p_hdr10_mastering->white_point_y >
- V4L2_HDR10_MASTERING_WHITE_POINT_Y_HIGH)
- return -EINVAL;
-
- if (p_hdr10_mastering->max_display_mastering_luminance <
- V4L2_HDR10_MASTERING_MAX_LUMA_LOW ||
- p_hdr10_mastering->max_display_mastering_luminance >
- V4L2_HDR10_MASTERING_MAX_LUMA_HIGH ||
- p_hdr10_mastering->min_display_mastering_luminance <
- V4L2_HDR10_MASTERING_MIN_LUMA_LOW ||
- p_hdr10_mastering->min_display_mastering_luminance >
- V4L2_HDR10_MASTERING_MIN_LUMA_HIGH)
+ /*
+ * SMPTE ST 2086 Annex A documents that CTA 861-G uses
+ * (0, 0) to indicate that the white point chromaticity
+ * is unknown.
+ */
+ if (p_hdr10_mastering->white_point_x ||
+ p_hdr10_mastering->white_point_y) {
+ if (p_hdr10_mastering->white_point_x <
+ V4L2_HDR10_MASTERING_WHITE_POINT_X_LOW ||
+ p_hdr10_mastering->white_point_x >
+ V4L2_HDR10_MASTERING_WHITE_POINT_X_HIGH ||
+ p_hdr10_mastering->white_point_y <
+ V4L2_HDR10_MASTERING_WHITE_POINT_Y_LOW ||
+ p_hdr10_mastering->white_point_y >
+ V4L2_HDR10_MASTERING_WHITE_POINT_Y_HIGH)
+ return -EINVAL;
+ }
+
+ /*
+ * SMPTE ST 2086 Annex A documents that CTA 861-G uses zero
+ * maximum and minimum luminance values to indicate that
+ * the corresponding values are unknown.
+ */
+ if (p_hdr10_mastering->max_display_mastering_luminance &&
+ (p_hdr10_mastering->max_display_mastering_luminance <
+ V4L2_HDR10_MASTERING_MAX_LUMA_LOW ||
+ p_hdr10_mastering->max_display_mastering_luminance >
+ V4L2_HDR10_MASTERING_MAX_LUMA_HIGH))
+ return -EINVAL;
+
+ if (p_hdr10_mastering->min_display_mastering_luminance &&
+ (p_hdr10_mastering->min_display_mastering_luminance <
+ V4L2_HDR10_MASTERING_MIN_LUMA_LOW ||
+ p_hdr10_mastering->min_display_mastering_luminance >
+ V4L2_HDR10_MASTERING_MIN_LUMA_HIGH))
return -EINVAL;
/* The following restriction comes from ITU-T Rec. H.265 spec */
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