2 files changed, 64 insertions, 0 deletions

diff --git a/docs/config_options.md b/docs/config_options.md
index f19df022a..661cfccce 100644
--- a/docs/config_options.md
+++ b/docs/config_options.md
@@ -190,6 +190,8 @@ If you define these options you will enable the associated feature, which may in
   * pin the DI on the WS2812 is hooked-up to
 * `#define RGBLIGHT_ANIMATIONS`
   * run RGB animations
+* `#define RGBLIGHT_LAYERS`
+  * Lets you define [lighting layers](feature_rgblight.md) that can be toggled on or off. Great for showing the current keyboard layer or caps lock state.
 * `#define RGBLED_NUM 12`
   * number of LEDs
 * `#define RGBLIGHT_SPLIT`
diff --git a/docs/feature_rgblight.md b/docs/feature_rgblight.md
index 69a6aaaed..a000241f8 100644
--- a/docs/feature_rgblight.md
+++ b/docs/feature_rgblight.md
@@ -172,6 +172,62 @@ const uint8_t RGBLED_KNIGHT_INTERVALS[] PROGMEM = {127, 63, 31};
 const uint8_t RGBLED_GRADIENT_RANGES[] PROGMEM = {255, 170, 127, 85, 64};
 ```
 
+## Lighting Layers
+
+By including `#define RGBLIGHT_LAYERS` in your `config.h` file you can enable lighting layers. These make
+it easy to use your underglow LEDs as status indicators to show which keyboard layer is currently active, or the state of caps lock, all without disrupting any animations. [Here's a video](https://youtu.be/uLGE1epbmdY) showing an example of what you can do. 
+
+To define a layer, we modify `keymap.c` to list out LED ranges and the colors we want to overlay on them using an array of `rgblight_segment_t` using the `RGBLIGHT_LAYER_SEGMENTS` macro. We can define multiple layers and enable/disable them independently:
+
+```c
+// Light LEDs 6 to 9 and 12 to 15 red when caps lock is active. Hard to ignore!
+const rgblight_segment_t PROGMEM my_capslock_layer[] = RGBLIGHT_LAYER_SEGMENTS(
+        {6, 4, HSV_RED},       // Light 4 LEDs, starting with LED 6
+        {12, 4, HSV_RED}       // Light 4 LEDs, starting with LED 12
+);
+// Light LEDs 9 & 10 in cyan when keyboard layer 1 is active
+const rgblight_segment_t PROGMEM my_layer1_layer[] = RGBLIGHT_LAYER_SEGMENTS(
+        {9, 2, HSV_CYAN}
+);
+// Light LEDs 11 & 12 in purple when keyboard layer 2 is active
+const rgblight_segment_t PROGMEM my_layer2_layer[] = RGBLIGHT_LAYER_SEGMENTS(
+        {11, 2, HSV_PURPLE}, 
+);
+// etc..
+```
+
+We combine these layers into an array using the `RGBLIGHT_LAYERS_LIST` macro, and assign it to the `rgblight_layers` variable during keyboard setup. Note that you can only define up to 8 lighting layers. Any extra layers will be ignored. Since the different lighting layers overlap, the order matters in the array, with later layers taking precedence:
+
+```c
+// Now define the array of layers. Later layers take precedence
+const rgblight_segment_t* const PROGMEM my_rgb_layers[] = RGBLIGHT_LAYERS_LIST(
+        my_capslock_layer,
+        my_layer1_layer,    // Overrides caps lock layer
+        my_layer2_layer     // Overrides other layers
+);
+
+void keyboard_post_init_user(void) {
+        // Enable the LED layers
+        rgblight_layers = my_rgb_layers;
+}
+```
+
+Finally, we enable and disable the lighting layers whenever the state of the keyboard changes:
+
+```c
+layer_state_t layer_state_set_user(layer_state_t state) {
+        // Both layers will light up if both kb layers are active
+        rgblight_set_layer_state(1, layer_state_cmp(state, 1));
+        rgblight_set_layer_state(2, layer_state_cmp(state, 2));
+        return state;
+}
+
+bool led_update_user(led_t led_state) {
+        rgblight_set_layer_state(0, led_state.caps_lock);
+        return true;
+}
+```
+
 ## Functions
 
 If you need to change your RGB lighting in code, for example in a macro to change the color whenever you switch layers, QMK provides a set of functions to assist you. See [`rgblight.h`](https://github.com/qmk/qmk_firmware/blob/master/quantum/rgblight.h) for the full list, but the most commonly used functions include:
@@ -263,6 +319,12 @@ rgblight_sethsv(HSV_GREEN, 2); // led 2
 |`rgblight_sethsv(h, s, v)`                  |Set effect range LEDs to the given HSV value where `h`/`s`/`v` are between 0 and 255 |
 |`rgblight_sethsv_noeeprom(h, s, v)`         |Set effect range LEDs to the given HSV value where `h`/`s`/`v` are between 0 and 255 (not written to EEPROM) |
 
+#### layer functions
+|Function                                    |Description  |
+|--------------------------------------------|-------------|
+|`rgblight_get_layer_state(i)`               |Returns `true` if lighting layer `i` is enabled |
+|`rgblight_set_layer_state(i, is_on)`        |Enable or disable lighting layer `i` based on value of `bool is_on` |
+
 #### query
 |Function               |Description      |
 |-----------------------|-----------------|