feat(shields): Make settings_reset shield reset all settings

Added a new CONFIG_ZMK_SETTINGS_RESET_ON_START option which enables init
code to call zmk_settings_erase(), and changed the settings_reset shield
to use it instead of CONFIG_ZMK_BLE_CLEAR_BONDS_ON_START, so it now
resets all settings instead of just clearing BLE bonds.

CONFIG_ZMK_BLE_CLEAR_BONDS_ON_START is left in place for now in case
someone still needs it. It may be replaced in the future once we find a
better way to repair a broken split connection.

app/Kconfig

@@ -565,6 +565,9 @@ endmenu
 
 if SETTINGS
 
+config ZMK_SETTINGS_RESET_ON_START
+    bool "Delete all persistent settings when the keyboard boots"
+
 config ZMK_SETTINGS_SAVE_DEBOUNCE
     int "Milliseconds to debounce settings saves"
     default 60000

app/boards/shields/settings_reset/settings_reset.conf

@@ -1 +1,4 @@
-CONFIG_ZMK_BLE_CLEAR_BONDS_ON_START=y
+CONFIG_SETTINGS=y
+CONFIG_ZMK_SETTINGS_RESET_ON_START=y
+# Disable BLE so splits don't try to re-pair until normal firmware is flashed.
+CONFIG_ZMK_BLE=n

app/src/settings/CMakeLists.txt

@@ -5,3 +5,5 @@ target_sources_ifdef(CONFIG_SETTINGS_NONE app PRIVATE reset_settings_none.c)
 target_sources_ifdef(CONFIG_SETTINGS_FCB app PRIVATE reset_settings_fcb.c)
 target_sources_ifdef(CONFIG_SETTINGS_FILE app PRIVATE reset_settings_file.c)
 target_sources_ifdef(CONFIG_SETTINGS_NVS app PRIVATE reset_settings_nvs.c)
+
+target_sources_ifdef(CONFIG_ZMK_SETTINGS_RESET_ON_START app PRIVATE reset_settings_on_start.c)

app/src/settings/reset_settings_on_start.c

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2023 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <zephyr/device.h>
+#include <zephyr/init.h>
+
+#include <zmk/settings.h>
+
+static int reset_settings_init(const struct device *dev) {
+    ARG_UNUSED(dev);
+    return zmk_settings_erase();
+}
+
+// Reset after the kernel is initialized but before any application code to
+// ensure settings are cleared before anything tries to use them.
+SYS_INIT(reset_settings_init, POST_KERNEL, CONFIG_APPLICATION_INIT_PRIORITY);

docs/docs/config/system.md

@@ -14,8 +14,9 @@ Definition file: [zmk/app/Kconfig](https://github.com/zmkfirmware/zmk/blob/main/
 ### General
 
 | Config                               | Type   | Description                                                                   | Default |
-| ----------------------------------- | ------ | ----------------------------------------------------------------------------- | ------- |
+| ------------------------------------ | ------ | ----------------------------------------------------------------------------- | ------- |
 | `CONFIG_ZMK_KEYBOARD_NAME`           | string | The name of the keyboard (max 16 characters)                                  |         |
+| `CONFIG_ZMK_SETTINGS_RESET_ON_START` | bool   | Clears all persistent settings from the keyboard at startup                   | n       |
 | `CONFIG_ZMK_SETTINGS_SAVE_DEBOUNCE`  | int    | Milliseconds to wait after a setting change before writing it to flash memory | 60000   |
 | `CONFIG_ZMK_WPM`                     | bool   | Enable calculating words per minute                                           | n       |
 | `CONFIG_HEAP_MEM_POOL_SIZE`          | int    | Size of the heap memory pool                                                  | 8192    |