Allow keyboards/keymaps to execute code at each main loop iteration

docs/custom_quantum_functions.md

@@ -287,6 +287,14 @@ This function gets called at every matrix scan, which is basically as often as t
 
 You should use this function if you need custom matrix scanning code. It can also be used for custom status output (such as LEDs or a display) or other functionality that you want to trigger regularly even when the user isn't typing.
 
+# Keyboard housekeeping
+
+* Keyboard/Revision: `void housekeeping_task_kb(void)`
+* Keymap: `void housekeeping_task_user(void)`
+
+This function gets called at the end of all QMK processing, before starting the next iteration. You can safely assume that QMK has dealt with the last matrix scan at the time that these functions are invoked -- layer states have been updated, USB reports have been sent, LEDs have been updated, and displays have been drawn.
+
+Similar to `matrix_scan_*`, these are called as often as the MCU can handle. To keep your board responsive, it's suggested to do as little as possible during these function calls, potentially throtting their behaviour if you do indeed require implementing something special.
 
 # Keyboard Idling/Wake Code
 

tmk_core/common/keyboard.c

@@ -229,6 +229,20 @@ __attribute__((weak)) bool is_keyboard_master(void) { return true; }
  */
 __attribute__((weak)) bool should_process_keypress(void) { return is_keyboard_master(); }
 
+/** \brief housekeeping_task_kb
+ *
+ * Override this function if you have a need to execute code for every keyboard main loop iteration.
+ * This is specific to keyboard-level functionality.
+ */
+__attribute__((weak)) void housekeeping_task_kb(void) {}
+
+/** \brief housekeeping_task_user
+ *
+ * Override this function if you have a need to execute code for every keyboard main loop iteration.
+ * This is specific to user/keymap-level functionality.
+ */
+__attribute__((weak)) void housekeeping_task_user(void) {}
+
 /** \brief keyboard_init
  *
  * FIXME: needs doc
@@ -309,6 +323,9 @@ void keyboard_task(void) {
     uint8_t keys_processed = 0;
 #endif
 
+    housekeeping_task_kb();
+    housekeeping_task_user();
+
 #if defined(OLED_DRIVER_ENABLE) && !defined(OLED_DISABLE_TIMEOUT)
     uint8_t ret = matrix_scan();
 #else

tmk_core/common/keyboard.h

@@ -69,6 +69,9 @@ void keyboard_pre_init_user(void);
 void keyboard_post_init_kb(void);
 void keyboard_post_init_user(void);
 
+void housekeeping_task_kb(void);
+void housekeeping_task_user(void);
+
 #ifdef __cplusplus
 }
 #endif

tmk_core/protocol/arm_atsam/main_arm_atsam.c

@@ -305,6 +305,10 @@ int main(void) {
             // dprintf("5v=%u 5vu=%u dlow=%u dhi=%u gca=%u gcd=%u\r\n", v_5v, v_5v_avg, v_5v_avg - V5_LOW, v_5v_avg - V5_HIGH, gcr_actual, gcr_desired);
         }
 #endif  // CONSOLE_ENABLE
+
+        // Run housekeeping
+        housekeeping_task_kb();
+        housekeeping_task_user();
     }
 
     return 1;

tmk_core/protocol/chibios/main.c

@@ -265,5 +265,9 @@ int main(void) {
 #ifdef RAW_ENABLE
         raw_hid_task();
 #endif
+
+        // Run housekeeping
+        housekeeping_task_kb();
+        housekeeping_task_user();
     }
 }

tmk_core/protocol/lufa/lufa.c

@@ -1104,6 +1104,10 @@ int main(void) {
 #if !defined(INTERRUPT_CONTROL_ENDPOINT)
         USB_USBTask();
 #endif
+
+        // Run housekeeping
+        housekeeping_task_kb();
+        housekeeping_task_user();
     }
 }
 

tmk_core/protocol/vusb/main.c

@@ -153,6 +153,10 @@ int main(void) {
                 console_task();
             }
 #endif
+
+            // Run housekeeping
+            housekeeping_task_kb();
+            housekeeping_task_user();
         } else if (suspend_wakeup_condition()) {
             usb_remote_wakeup();
         }