samples: display: Introduce Greyscale format support

This introduces L8 to the display sample

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

Author: VynDragon

samples/drivers/display/src/main.c

@@ -158,6 +158,13 @@ static void fill_buffer_mono(enum corner corner, uint8_t grey,
 	memset(buf, color, buf_size);
 }
 
+static inline void fill_buffer_l_8(enum corner corner, uint8_t grey, uint8_t *buf, size_t buf_size)
+{
+	for (size_t idx = 0; idx < buf_size; idx += 1) {
+		*(uint8_t *)(buf + idx) = grey;
+	}
+}
+
 static inline void fill_buffer_mono01(enum corner corner, uint8_t grey,
 				      uint8_t *buf, size_t buf_size)
 {
@@ -262,6 +269,10 @@ int main(void)
 		fill_buffer_fnc = fill_buffer_bgr565;
 		buf_size *= 2;
 		break;
+	case PIXEL_FORMAT_L_8:
+		bg_color = 0xFFu;
+		fill_buffer_fnc = fill_buffer_l_8;
+		break;
 	case PIXEL_FORMAT_MONO01:
 		bg_color = 0xFFu;
 		fill_buffer_fnc = fill_buffer_mono01;