Am 09.05.25 um 10:23 schrieb Thomas Zimmermann:
We have a number of drivers that offer simple gamma correction and palette modes. Depending on their hardware, the drivers process the provided data in similar ways. Unify the functionality in several DRM color-management helpers and update the drivers. The new helpers can load provided data or generate default data to load. With the drivers; ast, mgag200 ofdrm and vesadrm; gamma ramps are always 8 bit wide. For 24-bit color depth, 8-bit gamma ramps are being loaded to hardware as provided. For lower color depths the hardware often requires the gamma ramp to be reduced to the number of bits per pixel component, which the new helpers can do automatically. The exception is ast's hardware, which always uses 8-bit gamma ramps.
The default gamma ramp uses a factor of 1.0 (as has been the case in existing the per-driver implementations). A later update could change this to the common value of 2.2 or a system-specific value.
That might not be such a great idea. See https://people.freedesktop.org/~cbrill/dri-log/?channel=dri-devel&highlight_names=&date=2025-05-12&show_html=true
Helpers for palettes either load an 8-bit palette or generate a default palette with increasing luminance. The goal for the default is to keep the display content visible with black at index 0. A later update could possibly load a system-specific default palette. Thomas Zimmermann (5): drm: Add helpers for programming hardware gamma LUTs drm/ast: Use helpers for programming gamma ramps and palettes drm/mgag200: Use helpers for programming gamma ramps drm/ofdrm: Use helpers for programming gamma ramps drm/vesadrm: Use helpers for programming gamma ramps drivers/gpu/drm/ast/ast_mode.c | 69 +++++--- drivers/gpu/drm/drm_color_mgmt.c | 206 +++++++++++++++++++++++ drivers/gpu/drm/mgag200/mgag200_drv.h | 4 +- drivers/gpu/drm/mgag200/mgag200_g200er.c | 4 +- drivers/gpu/drm/mgag200/mgag200_g200ev.c | 4 +- drivers/gpu/drm/mgag200/mgag200_g200se.c | 4 +- drivers/gpu/drm/mgag200/mgag200_mode.c | 78 ++++----- drivers/gpu/drm/sysfb/ofdrm.c | 78 ++++----- drivers/gpu/drm/sysfb/vesadrm.c | 100 ++++------- include/drm/drm_color_mgmt.h | 27 +++ 10 files changed, 380 insertions(+), 194 deletions(-) base-commit: 842c3c276c106040f9b96d72b9df35ed6aed9ae9
-- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)
