Commit 7ff61177 authored by Thomas Zimmermann's avatar Thomas Zimmermann
Browse files

drm/color-mgmt: Prepare for RGB332 palettes 



Add helper drm_crtc_fill_palette_332(), which fills palettes with
RGB332 color data. Each color in RGB332 format serves as an index
into an 8-bit palette that stores the corresponding component-based
colors.

Vesadrm will use the new helper to emulate RGB formats on top of
framebuffers in C8 format.

v2:
- add comments on bit operations (Javier)

Signed-off-by: default avatarThomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: default avatarJavier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20250714151513.309475-6-tzimmermann@suse.de
parent 061963cd

drivers/gpu/drm/drm_color_mgmt.c

+34 −0
Original line number Diff line number Diff line
@@ -817,6 +817,40 @@ void drm_crtc_load_palette_8(struct drm_crtc *crtc, const struct drm_color_lut * 
}

EXPORT_SYMBOL(drm_crtc_load_palette_8);



static void fill_palette_332(struct drm_crtc *crtc, u16 r, u16 g, u16 b,

			     drm_crtc_set_lut_func set_palette)

{

	unsigned int i = (r << 5) | (g << 2) | b; /* 8-bit palette index */



	/* Expand R (3-bit) G (3-bit) and B (2-bit) values to 16-bit values */

	r = (r << 13) | (r << 10) | (r << 7) | (r << 4) | (r << 1) | (r >> 2);

	g = (g << 13) | (g << 10) | (g << 7) | (g << 4) | (g << 1) | (g >> 2);

	b = (b << 14) | (b << 12) | (b << 10) | (b << 8) | (b << 6) | (b << 4) | (b << 2) | b;



	set_palette(crtc, i, r, g, b);

}



/**

 * drm_crtc_fill_palette_332 - Programs a default palette for R332-like formats

 * @crtc: The displaying CRTC

 * @set_palette: Callback for programming the hardware gamma LUT

 *

 * Programs an RGB332 palette to hardware.

 */

void drm_crtc_fill_palette_332(struct drm_crtc *crtc, drm_crtc_set_lut_func set_palette)

{

	unsigned int r, g, b;



	/* Limits of 8-8-4 are the maximum number of values for each channel. */

	for (r = 0; r < 8; ++r) {

		for (g = 0; g < 8; ++g) {

			for (b = 0; b < 4; ++b)

				fill_palette_332(crtc, r, g, b, set_palette);

		}

	}

}

EXPORT_SYMBOL(drm_crtc_fill_palette_332);



static void fill_palette_8(struct drm_crtc *crtc, unsigned int i,

			   drm_crtc_set_lut_func set_palette)

{

include/drm/drm_color_mgmt.h

+1 −0
Original line number Diff line number Diff line
@@ -143,6 +143,7 @@ void drm_crtc_fill_gamma_555(struct drm_crtc *crtc, drm_crtc_set_lut_func set_ga 
void drm_crtc_load_palette_8(struct drm_crtc *crtc, const struct drm_color_lut *lut,

			     drm_crtc_set_lut_func set_palette);



void drm_crtc_fill_palette_332(struct drm_crtc *crtc, drm_crtc_set_lut_func set_palette);

void drm_crtc_fill_palette_8(struct drm_crtc *crtc, drm_crtc_set_lut_func set_palette);



#endif