On 2026-07-30 06:59, Pekka Paalanen wrote:
> On Wed, 22 Jul 2026 09:45:57 -0400
> Harry Wentland <[email protected]> wrote:
>
>> From: Chaitanya Kumar Borah <[email protected]>
>>
>> Introduce DRM_COLOROP_FIXED_MATRIX, a new colorop type representing a
>> hardware that performs a fixed matrix operation.
>>
>> Unlike CTM-based colorops, this block does not expose programmable
>> coefficients. Instead, userspace selects one of the predefined
>> hardware modes via a new FIXED_MATRIX_TYPE enum property. Supported modes
>> include common YCbCr->RGB and RGB709->RGB2020 conversions.
>>
>> v4:
>> - Add limited-range YCbCr-RGB conversion matrix enums (Robert)
>> - Document matrix values (Pekka)
>> - Clarify RGB709 to RGB2020 is a full-range matrix (Pekka)
>> - Fix confusing "CSC preset" doc (Pekka)
>>
>> v2:
>> - Naming changes (Pekka)
>>
>> v3:
>> - Fix NC matrix enum name and string (Melissa)
>> - Rebase
>>
>> Co-developed-by: Harry Wentland <[email protected]>
>> Signed-off-by: Chaitanya Kumar Borah <[email protected]>
>> Signed-off-by: Harry Wentland <[email protected]>
>> Reviewed-by: Melissa Wen <[email protected]>
>> Reviewed-by: Harry Wentland <[email protected]>
>> Reviewed-by: Robert Mader <[email protected]>
>> ---
>> drivers/gpu/drm/drm_atomic.c | 4 +
>> drivers/gpu/drm/drm_atomic_uapi.c | 7 ++
>> drivers/gpu/drm/drm_colorop.c | 109 ++++++++++++++++++++
>> include/drm/drm_colorop.h | 159 ++++++++++++++++++++++++++++++
>> include/uapi/drm/drm_mode.h | 12 +++
>> 5 files changed, 291 insertions(+)
>
>> diff --git a/drivers/gpu/drm/drm_colorop.c b/drivers/gpu/drm/drm_colorop.c
>> index 682fcc651525..e7ccf7d053b8 100644
>> --- a/drivers/gpu/drm/drm_colorop.c
>> +++ b/drivers/gpu/drm/drm_colorop.c
>> @@ -68,6 +68,7 @@ static const struct drm_prop_enum_list
>> drm_colorop_type_enum_list[] = {
>> { DRM_COLOROP_CTM_3X4, "3x4 Matrix"},
>> { DRM_COLOROP_MULTIPLIER, "Multiplier"},
>> { DRM_COLOROP_3D_LUT, "3D LUT"},
>> + { DRM_COLOROP_FIXED_MATRIX, "Fixed Matrix"},
>> };
>>
>> static const char * const colorop_curve_1d_type_names[] = {
>> @@ -90,6 +91,17 @@ static const struct drm_prop_enum_list
>> drm_colorop_lut3d_interpolation_list[] =
>> { DRM_COLOROP_LUT3D_INTERPOLATION_TETRAHEDRAL, "Tetrahedral" },
>> };
>>
>> +static const char * const colorop_fixed_matrix_type_names[] = {
>> + [DRM_COLOROP_FM_YCBCR601_FULL_RGB] = "YCbCr 601 Full to RGB",
>> + [DRM_COLOROP_FM_YCBCR601_LIMITED_RGB] = "YCbCr 601 Limited to RGB",
>> + [DRM_COLOROP_FM_YCBCR709_FULL_RGB] = "YCbCr 709 Full to RGB",
>> + [DRM_COLOROP_FM_YCBCR709_LIMITED_RGB] = "YCbCr 709 Limited to RGB",
>> + [DRM_COLOROP_FM_YCBCR2020_NC_FULL_RGB] = "YCbCr 2020 NC Full to RGB",
>> + [DRM_COLOROP_FM_YCBCR2020_NC_LIMITED_RGB] = "YCbCr 2020 NC Limited to
>> RGB",
>> + [DRM_COLOROP_FM_YCBCR_LIMITED_FULL] = "YCbCr limited to full",
>> + [DRM_COLOROP_FM_RGB709_RGB2020] = "RGB709 to RGB2020",
>> +};
>
>
>> diff --git a/include/drm/drm_colorop.h b/include/drm/drm_colorop.h
>> index 224fae40ed2b..92eb6463c39f 100644
>> --- a/include/drm/drm_colorop.h
>> +++ b/include/drm/drm_colorop.h
>> @@ -134,6 +134,146 @@ enum drm_colorop_curve_1d_type {
>> DRM_COLOROP_1D_CURVE_COUNT
>> };
>>
>> +/**
>> + * enum drm_colorop_fixed_matrix_type - type of Fixed Matrix
>> + *
>> + * Describes a Fixed Matrix operation to be applied by the
>> DRM_COLOROP_FIXED_MATRIX
>> + */
>> +enum drm_colorop_fixed_matrix_type {
>> + /**
>> + * @DRM_COLOROP_FM_YCBCR601_FULL_RGB:
>> + *
>> + * enum string "YCbCr 601 Full to RGB"
>> + *
>> + * Converts full-range YCbCr into full-range RGB using the BT.601
>> + * coefficients. Y is normalized to [0, 1] and Cb, Cr are centered
>> + * at 0 (the nominal 0.5 offset removed) before the matrix::
>> + *
>> + * | R | | 1.0 0.000000 1.402000 | | Y |
>> + * | G | = | 1.0 -0.344136 -0.714136 | x | Cb |
>> + * | B | | 1.0 1.772000 0.000000 | | Cr |
>> + */
>> + DRM_COLOROP_FM_YCBCR601_FULL_RGB,
>> +
>> + /**
>> + * @DRM_COLOROP_FM_YCBCR601_LIMITED_RGB:
>> + *
>> + * enum string "YCbCr 601 Limited to RGB"
>> + *
>> + * Converts limited- (narrow-) range YCbCr into full-range RGB using
>> + * the BT.601 coefficients. Before the matrix Y is offset by 16/255
>> + * and Cb, Cr are centered at 0, following the studio-range
>> + * convention of ITU-R BT.601::
>> + *
>> + * | R | | 1.164384 0.000000 1.596027 | | Y - 16/255 |
>> + * | G | = | 1.164384 -0.391762 -0.812968 | x | Cb |
>> + * | B | | 1.164384 2.017232 0.000000 | | Cr |
>> + */
>> + DRM_COLOROP_FM_YCBCR601_LIMITED_RGB,
>> +
>> + /**
>> + * @DRM_COLOROP_FM_YCBCR709_FULL_RGB:
>> + *
>> + * enum string "YCbCr 709 Full to RGB"
>> + *
>> + * Converts full-range YCbCr into full-range RGB using the BT.709
>> + * coefficients. Y is normalized to [0, 1] and Cb, Cr are centered
>> + * at 0 (the nominal 0.5 offset removed) before the matrix::
>> + *
>> + * | R | | 1.0 0.000000 1.574800 | | Y |
>> + * | G | = | 1.0 -0.187324 -0.468124 | x | Cb |
>> + * | B | | 1.0 1.855600 0.000000 | | Cr |
>> + */
>> + DRM_COLOROP_FM_YCBCR709_FULL_RGB,
>> +
>> + /**
>> + * @DRM_COLOROP_FM_YCBCR709_LIMITED_RGB:
>> + *
>> + * enum string "YCbCr 709 Limited to RGB"
>> + *
>> + * Converts limited- (narrow-) range YCbCr into full-range RGB using
>> + * the BT.709 coefficients. Before the matrix Y is offset by 16/255
>> + * and Cb, Cr are centered at 0, following the studio-range
>> + * convention of ITU-R BT.709::
>> + *
>> + * | R | | 1.164384 0.000000 1.792741 | | Y - 16/255 |
>> + * | G | = | 1.164384 -0.213249 -0.532909 | x | Cb |
>> + * | B | | 1.164384 2.112402 0.000000 | | Cr |
>> + */
>> + DRM_COLOROP_FM_YCBCR709_LIMITED_RGB,
>> +
>> + /**
>> + * @DRM_COLOROP_FM_YCBCR2020_NC_FULL_RGB:
>> + *
>> + * enum string "YCbCr 2020 NC Full to RGB"
>> + *
>> + * Converts full-range YCbCr into full-range RGB using the BT.2020
>> + * non-constant luminance coefficients. Y is normalized to [0, 1]
>> + * and Cb, Cr are centered at 0 (the nominal 0.5 offset removed)
>> + * before the matrix::
>> + *
>> + * | R | | 1.0 0.000000 1.474600 | | Y |
>> + * | G | = | 1.0 -0.164553 -0.571353 | x | Cb |
>> + * | B | | 1.0 1.881400 0.000000 | | Cr |
>> + */
>> + DRM_COLOROP_FM_YCBCR2020_NC_FULL_RGB,
>> +
>> + /**
>> + * @DRM_COLOROP_FM_YCBCR2020_NC_LIMITED_RGB:
>> + *
>> + * enum string "YCbCr 2020 NC Limited to RGB"
>> + *
>> + * Converts limited- (narrow-) range YCbCr into full-range RGB using
>> + * the BT.2020 non-constant luminance coefficients. Before the matrix
>> + * Y is offset by 16/255 and Cb, Cr are centered at 0, following the
>> + * studio-range convention of ITU-R BT.2020::
>> + *
>> + * | R | | 1.164384 0.000000 1.678674 | | Y - 16/255 |
>> + * | G | = | 1.164384 -0.187326 -0.650424 | x | Cb |
>> + * | B | | 1.164384 2.141772 0.000000 | | Cr |
>> + */
>> + DRM_COLOROP_FM_YCBCR2020_NC_LIMITED_RGB,
>> +
>> + /**
>> + * @DRM_COLOROP_FM_YCBCR_LIMITED_FULL:
>> + *
>> + * enum string "YCbCr limited to full"
>> + *
>> + * Converts limited- (narrow-) range YCbCr into full-range YCbCr.
>> + * Though not strictly a matrix operation it can be represented as
>> + * one. Luma is expanded by 255/219 and chroma by 255/224, keeping
>> + * the black level (16/255) and chroma neutral point (0.5) fixed::
>> + *
>> + * | Y' | | 1.164384 0.000000 0.000000 | | Y - 16/255 |
>> + * | Cb'-0.5 | = | 0.000000 1.138393 0.000000 | x | Cb - 0.5 |
>> + * | Cr'-0.5 | | 0.000000 0.000000 1.138393 | | Cr - 0.5 |
>> + */
>
> Hi Harry,
>
> the prime notation (Y') is often used to signify an electrical domain
> while in the same context stimulus variables without prime signify an
> optical domain. Using both forms here might cause some confusion.
> Instead of an equals sign, maybe you could use an arrow to avoid having
> to rename all YCbCr variables? (e.g. x ← x + 1)
>
> About the chroma offset for both ranges on all coefficients; it depends
> on the number of bits per channel B such that
>
> N = 1 << B
> offset = (N / 2) / (N - 1)
>
> I assume the drivers and hardware get this right, but I feel a little
> uncomfortable letting this approximation into the documentation since,
> strictly speaking, it's incorrect.
>
I'm dropping DRM_COLOROP_FM_YCBCR_LIMITED_FULL and DRM_COLOROP_FM_RGB709_RGB2020
from v5 because we don't have any good non-IGT usermode testing these currently,
to my knowledge.
Chaitanya, I expect you'll re-add them for your Intel series. Make sure to take
Pekka's comments into account then. Would like to see how these fit into any
compositor implementation.
Harry
>
>> + DRM_COLOROP_FM_YCBCR_LIMITED_FULL,
>> +
>> + /**
>> + * @DRM_COLOROP_FM_RGB709_RGB2020:
>> + *
>> + * enum string "RGB709 to RGB2020"
>> + *
>> + * Selects the matrix that converts full-range RGB with BT.709
>> + * primaries to full-range RGB with BT.2020 primaries. The
>> + * coefficients match the RGB-to-RGB conversion defined in
>> + * ITU-R BT.2087::
>> + *
>> + * | R2020 | | 0.6274 0.3293 0.0433 | | R709 |
>> + * | G2020 | = | 0.0691 0.9195 0.0114 | x | G709 |
>> + * | B2020 | | 0.0164 0.0880 0.8956 | | B709 |
>> + */
>> + DRM_COLOROP_FM_RGB709_RGB2020,
>> +
>> + /**
>> + * @DRM_COLOROP_FM_COUNT:
>> + *
>> + * enum value denoting the size of the enum
>> + */
>> + DRM_COLOROP_FM_COUNT
>> +};
>
> I have verified all the matrices listed above.
>
> I would prefer to see the notational issues addressed, but with or
> without:
>
> Reviewed-by: Pekka Paalanen <[email protected]>
>
>
> Thanks,
> pq
