add storage.erase_filesystem() to erase and reformat CIRCUITPY

main.c

@@ -245,7 +245,7 @@ int __attribute__((used)) main(void) {
     // Create a new filesystem only if we're not in a safe mode.
     // A power brownout here could make it appear as if there's
     // no SPI flash filesystem, and we might erase the existing one.
-    filesystem_init(safe_mode == NO_SAFE_MODE);
+    filesystem_init(safe_mode == NO_SAFE_MODE, false);
 
     // Reset everything and prep MicroPython to run boot.py.
     reset_port();

ports/atmel-samd/supervisor/filesystem.c

@@ -50,7 +50,7 @@ static void make_empty_file(FATFS *fatfs, const char *path) {
 
 // we don't make this function static because it needs a lot of stack and we
 // want it to be executed without using stack within main() function
-void filesystem_init(bool create_allowed) {
+void filesystem_init(bool create_allowed, bool create_force) {
     // init the vfs object
     fs_user_mount_t *vfs_fat = &fs_user_mount_flash;
     vfs_fat->flags = 0;
@@ -59,11 +59,11 @@ void filesystem_init(bool create_allowed) {
     // try to mount the flash
     FRESULT res = f_mount(&vfs_fat->fatfs);
 
-    if (res == FR_NO_FILESYSTEM && create_allowed) {
+    if ((res == FR_NO_FILESYSTEM && create_allowed) || create_force) {
-        // no filesystem so create a fresh one
+        // No filesystem so create a fresh one, or reformat has been requested.
         uint8_t working_buf[_MAX_SS];
         res = f_mkfs(&vfs_fat->fatfs, FM_FAT, 0, working_buf, sizeof(working_buf));
-        // Flush the new file system to make sure its repaired immediately.
+        // Flush the new file system to make sure it's repaired immediately.
         flash_flush();
         if (res != FR_OK) {
             return;

shared-bindings/storage/__init__.c

@@ -131,6 +131,24 @@ mp_obj_t storage_getmount(const mp_obj_t mnt_in) {
 }
 MP_DEFINE_CONST_FUN_OBJ_1(storage_getmount_obj, storage_getmount);
 
+//| .. function:: erase_filesystem()
+//|
+//|   Erase and re-create the ``CIRCUITPY`` filesystem. Then call
+//|   `microcontroller.reset()` to restart CircuitPython and have the
+//|   host computer remount CIRCUITPY.
+//|
+//|   This function can be called from the REPL when ``CIRCUITPY``
+//|   has become corrupted.
+//|
+//|   .. warning:: All the data on ``CIRCUITPY`` will be lost, and
+//|        CircuitPython will restart.
+
+mp_obj_t storage_erase_filesystem(void) {
+    common_hal_storage_erase_filesystem();
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_0(storage_erase_filesystem_obj, storage_erase_filesystem);
+
 STATIC const mp_rom_map_elem_t storage_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_storage) },
 
@@ -138,6 +156,7 @@ STATIC const mp_rom_map_elem_t storage_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_umount), MP_ROM_PTR(&storage_umount_obj) },
     { MP_ROM_QSTR(MP_QSTR_remount), MP_ROM_PTR(&storage_remount_obj) },
     { MP_ROM_QSTR(MP_QSTR_getmount), MP_ROM_PTR(&storage_getmount_obj) },
+    { MP_ROM_QSTR(MP_QSTR_erase_filesystem), MP_ROM_PTR(&storage_erase_filesystem_obj) },
 
     //| .. class:: VfsFat(block_device)
     //|

shared-bindings/storage/__init__.h

@@ -35,5 +35,6 @@ void common_hal_storage_umount_path(const char* path);
 void common_hal_storage_umount_object(mp_obj_t vfs_obj);
 void common_hal_storage_remount(const char* path, bool readonly);
 mp_obj_t common_hal_storage_getmount(const char* path);
+void common_hal_storage_erase_filesystem(void);
 
 #endif  // MICROPY_INCLUDED_SHARED_BINDINGS_STORAGE___INIT___H

shared-module/storage/__init__.c

@@ -32,7 +32,9 @@
 #include "py/mperrno.h"
 #include "py/obj.h"
 #include "py/runtime.h"
+#include "shared-bindings/microcontroller/__init__.h"
 #include "shared-bindings/storage/__init__.h"
+#include "supervisor/filesystem.h"
 
 STATIC mp_obj_t mp_vfs_proxy_call(mp_vfs_mount_t *vfs, qstr meth_name, size_t n_args, const mp_obj_t *args) {
     if (vfs == MP_VFS_NONE) {
@@ -125,3 +127,9 @@ void common_hal_storage_umount_path(const char* mount_path) {
 mp_obj_t common_hal_storage_getmount(const char *mount_path) {
     return storage_object_from_path(mount_path);
 }
+
+void common_hal_storage_erase_filesystem(void) {
+    filesystem_init(false, true);   // Force a re-format.
+    common_hal_mcu_reset();
+    // We won't actually get here, since we're resetting.
+}

supervisor/filesystem.h

@@ -29,7 +29,7 @@
 
 #include <stdbool.h>
 
-void filesystem_init(bool create_allowed);
+void filesystem_init(bool create_allowed, bool create_force);
 void filesystem_flush(void);
 void filesystem_writable_by_python(bool writable);
 bool filesystem_present(void);