From f915455dae30aa3d031c82109261b3b7cfe8e438 Mon Sep 17 00:00:00 2001
From: 3d-gussner <3d.gussner@gmail.com>
Date: Tue, 22 Apr 2025 18:42:22 +0200
Subject: [PATCH] Fix M256 S parameter

---
 Firmware/Marlin_main.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Firmware/Marlin_main.cpp b/Firmware/Marlin_main.cpp
index b7bc899b1..65d1799a6 100644
--- a/Firmware/Marlin_main.cpp
+++ b/Firmware/Marlin_main.cpp
@@ -6663,7 +6663,12 @@ void process_commands()
       if (backlightSupport) {
         if (code_seen('B') ) backlightLevel_HIGH = code_value_uint8();
         if (code_seen('D')) backlightLevel_LOW = code_value_uint8();
-        if (code_seen('S')) backlightMode = max(static_cast<Backlight_Mode>(code_value_uint8()), BACKLIGHT_MODE_AUTO);
+        if (code_seen('S')) {
+          uint8_t mode = code_value_uint8();
+          if (mode <= BACKLIGHT_MODE_AUTO) {
+            backlightMode = static_cast<Backlight_Mode>(mode);
+         }
+        }
         if (code_seen('T')) backlightTimer_period = constrain(code_value_short(), LCD_BACKLIGHT_TIMEOUT, LCD_BACKLIGHT_TIMEOUT*60);
         printf_P(PSTR("M256 B%d D%d S%d T%u\n"), backlightLevel_HIGH, backlightLevel_LOW, backlightMode, backlightTimer_period);
         backlight_save();