Cleanup/rgb matrix (#5811)

[qmk_firmware.git] / docs / feature_rgb_matrix.md

diff --git a/docs/feature_rgb_matrix.md b/docs/feature_rgb_matrix.md
index 1e4341467617319b78bc588cf686b6555e115412..e29433a4bf5315866f2d820f40ea274480cba8a6 100644 (file)
--- a/docs/feature_rgb_matrix.md
+++ b/docs/feature_rgb_matrix.md
@@ -30,9 +30,11 @@ Configure the hardware via your `config.h`:
 #define DRIVER_COUNT 2
 #define DRIVER_1_LED_TOTAL 25
 #define DRIVER_2_LED_TOTAL 24
-#define DRIVER_LED_TOTAL DRIVER_1_LED_TOTAL + DRIVER_2_LED_TOTAL
+#define DRIVER_LED_TOTAL (DRIVER_1_LED_TOTAL + DRIVER_2_LED_TOTAL)
 ```
 
+!> Note the parentheses, this is so when `DRIVER_LED_TOTAL` is used in code and expanded, the values are added together before any additional math is applied to them. As an example, `rand() % (DRIVER_1_LED_TOTAL + DRIVER_2_LED_TOTAL)` will give very different results than `rand() % DRIVER_1_LED_TOTAL + DRIVER_2_LED_TOTAL`.
+
 Currently only 2 drivers are supported, but it would be trivial to support all 4 combinations.
 
 Define these arrays listing all the LEDs in your `<keyboard>.c`: