modules: lvgl: Introduce Greyscale support

This introduces support glue for L8 greyscale

Signed-off-by: Camille BAUD <mail@massdriver.space>

Author: VynDragon

modules/lvgl/CMakeLists.txt

@@ -313,6 +313,7 @@ zephyr_library_sources(
     lvgl.c
     lvgl_display.c
     lvgl_display_mono.c
+    lvgl_display_8bit.c
     lvgl_display_16bit.c
     lvgl_display_24bit.c
     lvgl_display_32bit.c

modules/lvgl/include/lvgl_display.h

@@ -30,6 +30,7 @@ struct lvgl_display_flush {
 };
 
 void lvgl_flush_cb_mono(lv_display_t *display, const lv_area_t *area, uint8_t *px_map);
+void lvgl_flush_cb_8bit(lv_display_t *display, const lv_area_t *area, uint8_t *px_map);
 void lvgl_flush_cb_16bit(lv_display_t *display, const lv_area_t *area, uint8_t *px_map);
 void lvgl_flush_cb_24bit(lv_display_t *display, const lv_area_t *area, uint8_t *px_map);
 void lvgl_flush_cb_32bit(lv_display_t *display, const lv_area_t *area, uint8_t *px_map);

modules/lvgl/lvgl.c

@@ -146,6 +146,9 @@ static int lvgl_allocate_rendering_buffers(lv_display_t *display)
 	case PIXEL_FORMAT_RGB_565:
 		buf_size = 2 * buf_nbr_pixels;
 		break;
+	case PIXEL_FORMAT_L_8:
+		buf_size = buf_nbr_pixels;
+		break;
 	case PIXEL_FORMAT_MONO01:
 	case PIXEL_FORMAT_MONO10:
 		buf_size = buf_nbr_pixels / 8 + 8;

modules/lvgl/lvgl_display.c

@@ -96,6 +96,12 @@ int set_lvgl_rendering_cb(lv_display_t *display)
 		lv_display_add_event_cb(display, lvgl_rounder_cb, LV_EVENT_INVALIDATE_AREA,
 					display);
 		break;
+	case PIXEL_FORMAT_L_8:
+		lv_display_set_color_format(display, LV_COLOR_FORMAT_L8);
+		lv_display_set_flush_cb(display, lvgl_flush_cb_8bit);
+		lv_display_add_event_cb(display, lvgl_rounder_cb, LV_EVENT_INVALIDATE_AREA,
+					display);
+		break;
 	case PIXEL_FORMAT_MONO01:
 	case PIXEL_FORMAT_MONO10:
 		lv_display_set_color_format(display, LV_COLOR_FORMAT_I1);

modules/lvgl/lvgl_display_8bit.c

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2025 MASSDRIVER EI (massdriver.space)
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+#include <lvgl.h>
+#include "lvgl_display.h"
+
+void lvgl_flush_cb_8bit(lv_display_t *display, const lv_area_t *area, uint8_t *px_map)
+{
+	uint16_t w = area->x2 - area->x1 + 1;
+	uint16_t h = area->y2 - area->y1 + 1;
+	struct lvgl_display_flush flush;
+
+	flush.display = display;
+	flush.x = area->x1;
+	flush.y = area->y1;
+	flush.desc.buf_size = w * h;
+	flush.desc.width = w;
+	flush.desc.pitch = w;
+	flush.desc.height = h;
+	flush.buf = (void *)px_map;
+
+	lvgl_flush_display(&flush);
+}