modules: lvgl: handle byte-swapped RGB565 displays

Displays that advertise PIXEL_FORMAT_RGB_565X need LVGL to render
RGB565 pixels in byte-swapped order. Treating RGB_565X like native
RGB_565 makes non-palindromic colors decode as the wrong hue on the
panel.

Signed-off-by: Fabian Blatz <fabianblatz@gmail.com>
Co-authored-by: Carlo Caione <ccaione@baylibre.com>

Author: faxe1008

modules/lvgl/lvgl.c

@@ -178,6 +178,7 @@ static int lvgl_allocate_rendering_buffers(lv_display_t *display)
 		buf_size = 3 * buf_nbr_pixels;
 		break;
 	case PIXEL_FORMAT_RGB_565:
+	case PIXEL_FORMAT_RGB_565X:
 		buf_size = 2 * buf_nbr_pixels;
 		break;
 	case PIXEL_FORMAT_L_8:

modules/lvgl/lvgl_display.c

@@ -90,12 +90,17 @@ int set_lvgl_rendering_cb(lv_display_t *display)
 					display);
 		break;
 	case PIXEL_FORMAT_RGB_565:
-	case PIXEL_FORMAT_RGB_565X:
 		lv_display_set_color_format(display, LV_COLOR_FORMAT_RGB565);
 		lv_display_set_flush_cb(display, lvgl_flush_cb_16bit);
 		lv_display_add_event_cb(display, lvgl_rounder_cb, LV_EVENT_INVALIDATE_AREA,
 					display);
 		break;
+	case PIXEL_FORMAT_RGB_565X:
+		lv_display_set_color_format(display, LV_COLOR_FORMAT_RGB565_SWAPPED);
+		lv_display_set_flush_cb(display, lvgl_flush_cb_16bit);
+		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);