Backlight - New option : BACKLIGHT_CAPS_LOCK (#4769)

* [BACKLIGHT_CAPS_LOCK_INDICATOR] Use backlight toggling as Caps Lock LED

I've implemented this feature because S65-X doesn't have LED indicators
and the existing led_set_kb(usb_led) function try to use backlight as
indicator but that creates an inconsistency with backlight_config state.

- define `BACKLIGHT_CAPS_LOCK_INDICATOR` to enable Caps Lock indicator
  using backlight (for keyboards without dedicated LED)

- Don't turn off LED indicators when suspend because backlight is
  already turned off. Else led_set(0) will turn back on backlight.

- Documentation has been updated

* [BACKLIGHT_CAPS_LOCK_INDICATOR] Turn off all LED indicators except Caps Lock if BACKLIGHT_CAPS_LOCK_INDICATOR

* [BACKLIGHT_CAPS_LOCK] Rename BACKLIGHT_CAPS_LOCK_INDICATOR

* [BACKLIGHT_CAPS_LOCK] Use new IS_LED_ON method

1 files changed, 18 insertions, 0 deletions

diff --git a/quantum/quantum.c b/quantum/quantum.c
index 5d8ffe34eb..c1829c7685 100644
--- a/quantum/quantum.c
+++ b/quantum/quantum.c
@@ -1448,6 +1448,24 @@ void led_set(uint8_t usb_led)
     //     PORTE &= ~(1<<6);
     // }
 
+#if defined(BACKLIGHT_CAPS_LOCK) && defined(BACKLIGHT_ENABLE)
+  // Use backlight as Caps Lock indicator
+  uint8_t bl_toggle_lvl = 0;
+
+  if (IS_LED_ON(usb_led, USB_LED_CAPS_LOCK) && !backlight_config.enable) {
+    // Turning Caps Lock ON and backlight is disabled in config
+    // Toggling backlight to the brightest level
+    bl_toggle_lvl = BACKLIGHT_LEVELS;
+  } else if (IS_LED_OFF(usb_led, USB_LED_CAPS_LOCK) && backlight_config.enable) {
+    // Turning Caps Lock OFF and backlight is enabled in config
+    // Toggling backlight and restoring config level
+    bl_toggle_lvl = backlight_config.level;
+  }
+
+  // Set level without modify backlight_config to keep ability to restore state
+  backlight_set(bl_toggle_lvl);
+#endif
+
   led_set_kb(usb_led);
 }