feat: Add function to erase all settings

Added a zmk_settings_erase() function to clear all saved settings. This
does not go through Zephyr's settings subsystem, but instead directly
clears the data from the setting storage backend, so a reboot is needed
for it to take effect.

app/CMakeLists.txt

@@ -99,5 +99,6 @@ target_sources_ifdef(CONFIG_ZMK_LOW_PRIORITY_WORK_QUEUE app PRIVATE src/workqueu
 target_sources(app PRIVATE src/main.c)
 
 add_subdirectory(src/display/)
+add_subdirectory_ifdef(CONFIG_SETTINGS src/settings/)
 
 zephyr_cc_option(-Wfatal-errors)

app/include/zmk/settings.h

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2023 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#pragma once
+
+/**
+ * Erases all saved settings.
+ *
+ * @note This does not automatically update any code using Zephyr's settings
+ * subsystem. This should typically be followed by a call to sys_reboot().
+ */
+int zmk_settings_erase(void);

app/src/settings/CMakeLists.txt

@@ -0,0 +1,7 @@
+# Copyright (c) 2023 The ZMK Contributors
+# SPDX-License-Identifier: MIT
+
+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)

app/src/settings/reset_settings_fcb.c

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2023 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <zmk/settings.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+int zmk_settings_erase(void) {
+    LOG_ERR("Settings reset is not implemented for deprecated FCB backend.");
+    return -ENOSYS;
+}

app/src/settings/reset_settings_file.c

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2023 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <zephyr/fs/fs.h>
+
+#include <zmk/settings.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+int zmk_settings_erase(void) {
+    LOG_INF("Erasing settings file");
+
+    int rc = fs_unlink(CONFIG_SETTINGS_FS_FILE);
+    if (rc) {
+        LOG_ERR("Failed to unlink '%s': %d", CONFIG_SETTINGS_FS_FILE, rc);
+    }
+
+    return rc;
+}

app/src/settings/reset_settings_none.c

@@ -0,0 +1,12 @@
+/*
+ * Copyright (c) 2023 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <zmk/settings.h>
+
+int zmk_settings_erase(void) {
+    // No storage backend; nothing to do
+    return 0;
+}

app/src/settings/reset_settings_nvs.c

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2023 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <zephyr/device.h>
+#include <zephyr/devicetree.h>
+#include <zephyr/storage/flash_map.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+// SETTINGS_PARTITION must match settings_nvs.c
+#if DT_HAS_CHOSEN(zephyr_settings_partition)
+#define SETTINGS_PARTITION DT_FIXED_PARTITION_ID(DT_CHOSEN(zephyr_settings_partition))
+#else
+#define SETTINGS_PARTITION FIXED_PARTITION_ID(storage_partition)
+#endif
+
+int zmk_settings_erase(void) {
+    LOG_INF("Erasing settings flash partition");
+
+    const struct flash_area *fa;
+    int rc = flash_area_open(SETTINGS_PARTITION, &fa);
+    if (rc) {
+        LOG_ERR("Failed to open settings flash: %d", rc);
+        return rc;
+    }
+
+    rc = flash_area_erase(fa, 0, fa->fa_size);
+    if (rc) {
+        LOG_ERR("Failed to erase settings flash: %d", rc);
+    }
+
+    flash_area_close(fa);
+
+    return rc;
+}