nrf/main: Add auto mount and auto format hook for internal flash FS.

ports/nrf/main.c

@@ -76,6 +76,13 @@
 #include "usb_cdc.h"
 #endif
 
+#if MICROPY_HW_ENABLE_INTERNAL_FLASH_STORAGE
+#include "extmod/vfs_fat.h"
+#include "lib/oofatfs/ff.h"
+#include "extmod/vfs.h"
+#include "flashbdev.h"
+#endif
+
 void do_str(const char *src, mp_parse_input_kind_t input_kind) {
     mp_lexer_t *lex = mp_lexer_new_from_str_len(MP_QSTR__lt_stdin_gt_, src, strlen(src), 0);
     if (lex == NULL) {
@@ -99,6 +106,28 @@ void do_str(const char *src, mp_parse_input_kind_t input_kind) {
 extern uint32_t _heap_start;
 extern uint32_t _heap_end;
 
+#if MICROPY_HW_ENABLE_INTERNAL_FLASH_STORAGE
+STATIC int vfs_mount_and_chdir(mp_obj_t bdev, mp_obj_t mount_point) {
+    nlr_buf_t nlr;
+    mp_int_t ret = -MP_EIO;
+    if (nlr_push(&nlr) == 0) {
+        mp_obj_t args[] = { bdev, mount_point };
+        mp_vfs_mount(2, args, (mp_map_t *)&mp_const_empty_map);
+        mp_vfs_chdir(mount_point);
+        ret = 0; // success
+        nlr_pop();
+    } else {
+        mp_obj_base_t *exc = nlr.ret_val;
+        if (mp_obj_is_subclass_fast(MP_OBJ_FROM_PTR(exc->type), MP_OBJ_FROM_PTR(&mp_type_OSError))) {
+            mp_obj_t v = mp_obj_exception_get_value(MP_OBJ_FROM_PTR(exc));
+            mp_obj_get_int_maybe(v, &ret); // get errno value
+            ret = -ret;
+        }
+    }
+    return ret;
+}
+#endif
+
 int main(int argc, char **argv) {
 
 
@@ -169,6 +198,23 @@ soft_reset:
 
     pin_init0();
 
+    #if MICROPY_HW_ENABLE_INTERNAL_FLASH_STORAGE
+    flashbdev_init();
+
+    // Try to mount the flash on "/flash" and chdir to it for the boot-up directory.
+    mp_obj_t mount_point = MP_OBJ_NEW_QSTR(MP_QSTR__slash_flash);
+    int ret = vfs_mount_and_chdir((mp_obj_t)&nrf_flash_obj, mount_point);
+
+    if ((ret == -MP_ENODEV) || (ret == -MP_EIO)) {
+        pyexec_frozen_module("_mkfs.py"); // Frozen script for formatting flash filesystem.
+        ret = vfs_mount_and_chdir((mp_obj_t)&nrf_flash_obj, mount_point);
+    }
+
+    if (ret != 0) {
+        printf("MPY: can't mount flash\n");
+    }
+    #endif
+
     #if MICROPY_MBFS
     microbit_filesystem_init();
     #endif