Re: [PATCH 00/11] drm/vkms: improve color curve LUTs precision

[Robert Mader]

Thanks a lot for the series!

I'm using it as part of a branch [1] to test my/our Weston post-blend 
color-op pipeline implementation [2] - including additional commits 
using the new script to add gamma 2.2 and 2.4 [3] curves. The Weston 
tests compare the vkms output against the GL renderer for e.g. NV12 
bt709-limited-range bt1886/gamma2.4 content - successfully (i.e. the 
results match very closely).

I also went through the commits and didn't spot any more issues. Thus 
with the 32bit issues raised by the bot addressed the whole series is:

Reviewed-by: Robert Mader <robert.mader@xxxxxxxxxxxxx>

Tested-by: Robert Mader <robert.mader@xxxxxxxxxxxxx>

Best regards,

Robert

---

1: https://gitlab.com/rmader/linux/-/commits/post-blend-2026-11-02

2: https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/2157

3: For SDR video, see 
https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/539

On 04.08.26 22:33, Leandro Ribeiro wrote:
> Currently VKMS only supports uniform LUTs. Besides the userspace
> provided LUTs, it also represents color curves with LUTs, as it can't
> simply implement the continuous curve formulas (floating-point would be
> required).
>
> This adds support to represent color curves with non-uniform LUTs,
> improving the precision significantly. It also provides a script
> that was used to create these LUTs.
>
> The optimized LUTs use more samples in regions where the interpolation
> and quantization errors are higher (usually in regions with a steeper
> slope). The LUT generator script compares different strategies and uses
> greedy subdivision, which outperformed the other methods, to generate
> the optimized LUTs for VKMS.
>
> Leandro Ribeiro (11):
>    drm/vkms: rename VKMS_LUT_SIZE to VKMS_GAMMA_LUT_SIZE
>    drm/vkms: allow color curve LUTs to have different sizes
>    drm/vkms: remove TEST_LUT_SIZE
>    drm/vkms: remove linear_eotf
>    drm/vkms: improve the way in which we access LUT member
>    drm/vkms: rename struct vkms_color_lut::base to y
>    drm/vkms: rename get_lut_index() to get_uniform_lut_index()
>    drm/vkms: add support to non-uniform LUT for internal color curves
>    drm/vkms: test sRGB and inverse sRGB LUTs using more samples
>    drm/vkms: add script to create optimized LUTs for color curves
>    drm/vkms: replace uniform sRGB LUT and its inverse with optimal ones
>
>   .../gpu/drm/vkms/scripts/color-curve-lut.py   |  561 +++++++
>   drivers/gpu/drm/vkms/tests/vkms_color_test.c  |   46 +-
>   drivers/gpu/drm/vkms/vkms_composer.c          |  127 +-
>   drivers/gpu/drm/vkms/vkms_composer.h          |    2 +-
>   drivers/gpu/drm/vkms/vkms_crtc.c              |    4 +-
>   drivers/gpu/drm/vkms/vkms_drv.c               |    2 +-
>   drivers/gpu/drm/vkms/vkms_drv.h               |   13 +-
>   drivers/gpu/drm/vkms/vkms_luts.c              | 1469 ++++++++---------
>   drivers/gpu/drm/vkms/vkms_luts.h              |    3 -
>   9 files changed, 1383 insertions(+), 844 deletions(-)
>   create mode 100644 drivers/gpu/drm/vkms/scripts/color-curve-lut.py
--
Robert Mader
Consultant Software Developer

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