stm32: Generalise flash mounting code so it supports arbitrary FS.

This commit refactors and generalises the boot-mount routine on stm32 so
that it can mount filesystems of arbitrary type.  That is, it no longer
assumes that the filesystem is FAT.  It does this by using mp_vfs_mount()
which does auto-detection of the filesystem type.

ports/stm32/factoryreset.c

@@ -25,6 +25,11 @@
  */
 
 #include "py/runtime.h"
+#include "py/mperrno.h"
+#include "extmod/vfs_fat.h"
+#include "systick.h"
+#include "led.h"
+#include "storage.h"
 #include "factoryreset.h"
 
 #if MICROPY_HW_ENABLE_STORAGE
@@ -96,4 +101,31 @@ MP_WEAK void factory_reset_make_files(FATFS *fatfs) {
     }
 }
 
+MP_WEAK int factory_reset_create_filesystem(void) {
+    // LED on to indicate creation of local filesystem
+    led_state(PYB_LED_GREEN, 1);
+    uint32_t start_tick = HAL_GetTick();
+
+    fs_user_mount_t vfs;
+    pyb_flash_init_vfs(&vfs);
+    uint8_t working_buf[FF_MAX_SS];
+    FRESULT res = f_mkfs(&vfs.fatfs, FM_FAT, 0, working_buf, sizeof(working_buf));
+    if (res != FR_OK) {
+        mp_printf(&mp_plat_print, "MPY: can't create flash filesystem\n");
+        return -MP_ENODEV;
+    }
+
+    // Set label
+    f_setlabel(&vfs.fatfs, MICROPY_HW_FLASH_FS_LABEL);
+
+    // Populate the filesystem with factory files
+    factory_reset_make_files(&vfs.fatfs);
+
+    // Keep LED on for at least 200ms
+    systick_wait_at_least(start_tick, 200);
+    led_state(PYB_LED_GREEN, 0);
+
+    return 0; // success
+}
+
 #endif // MICROPY_HW_ENABLE_STORAGE

ports/stm32/factoryreset.h

@@ -29,5 +29,6 @@
 #include "lib/oofatfs/ff.h"
 
 void factory_reset_make_files(FATFS *fatfs);
+int factory_reset_create_filesystem(void);
 
 #endif // MICROPY_INCLUDED_STM32_FACTORYRESET_H

ports/stm32/main.c

@@ -30,6 +30,7 @@
 #include "py/runtime.h"
 #include "py/stackctrl.h"
 #include "py/gc.h"
+#include "py/mperrno.h"
 #include "py/mphal.h"
 #include "lib/mp-readline/readline.h"
 #include "lib/utils/pyexec.h"
@@ -81,10 +82,6 @@
 STATIC pyb_thread_t pyb_thread_main;
 #endif
 
-#if MICROPY_HW_ENABLE_STORAGE
-STATIC fs_user_mount_t fs_user_mount_flash;
-#endif
-
 #if defined(MICROPY_HW_UART_REPL)
 #ifndef MICROPY_HW_UART_REPL_RXBUF
 #define MICROPY_HW_UART_REPL_RXBUF (260)
@@ -159,65 +156,51 @@ STATIC mp_obj_t pyb_main(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_a
 MP_DEFINE_CONST_FUN_OBJ_KW(pyb_main_obj, 1, pyb_main);
 
 #if MICROPY_HW_ENABLE_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;
+}
+
 // avoid inlining to avoid stack usage within main()
 MP_NOINLINE STATIC bool init_flash_fs(uint reset_mode) {
-    // init the vfs object
-    fs_user_mount_t *vfs_fat = &fs_user_mount_flash;
-    vfs_fat->blockdev.flags = 0;
-    pyb_flash_init_vfs(vfs_fat);
+    if (reset_mode == 3) {
+        // Asked by user to reset filesystem
+        factory_reset_create_filesystem();
+    }
 
-    // try to mount the flash
-    FRESULT res = f_mount(&vfs_fat->fatfs);
+    // Try to mount the flash on "/flash" and chdir to it for the boot-up directory.
+    mp_obj_t bdev = MP_OBJ_FROM_PTR(&pyb_flash_obj);
+    mp_obj_t mount_point = MP_OBJ_NEW_QSTR(MP_QSTR__slash_flash);
+    int ret = vfs_mount_and_chdir(bdev, mount_point);
 
-    if (reset_mode == 3 || res == FR_NO_FILESYSTEM) {
-        // no filesystem, or asked to reset it, so create a fresh one
-
-        // LED on to indicate creation of LFS
-        led_state(PYB_LED_GREEN, 1);
-        uint32_t start_tick = HAL_GetTick();
-
-        uint8_t working_buf[FF_MAX_SS];
-        res = f_mkfs(&vfs_fat->fatfs, FM_FAT, 0, working_buf, sizeof(working_buf));
-        if (res == FR_OK) {
-            // success creating fresh LFS
-        } else {
-            printf("MPY: can't create flash filesystem\n");
-            return false;
+    if (ret == -MP_ENODEV && reset_mode != 3) {
+        // No filesystem (and didn't already create one), try to create a fresh one
+        ret = factory_reset_create_filesystem();
+        if (ret == 0) {
+            ret = vfs_mount_and_chdir(bdev, mount_point);
         }
+    }
 
-        // set label
-        f_setlabel(&vfs_fat->fatfs, MICROPY_HW_FLASH_FS_LABEL);
-
-        // populate the filesystem with factory files
-        factory_reset_make_files(&vfs_fat->fatfs);
-
-        // keep LED on for at least 200ms
-        systick_wait_at_least(start_tick, 200);
-        led_state(PYB_LED_GREEN, 0);
-    } else if (res == FR_OK) {
-        // mount sucessful
-    } else {
-    fail:
+    if (ret != 0) {
         printf("MPY: can't mount flash\n");
         return false;
     }
 
-    // mount the flash device (there should be no other devices mounted at this point)
-    // we allocate this structure on the heap because vfs->next is a root pointer
-    mp_vfs_mount_t *vfs = m_new_obj_maybe(mp_vfs_mount_t);
-    if (vfs == NULL) {
-        goto fail;
-    }
-    vfs->str = "/flash";
-    vfs->len = 6;
-    vfs->obj = MP_OBJ_FROM_PTR(vfs_fat);
-    vfs->next = NULL;
-    MP_STATE_VM(vfs_mount_table) = vfs;
-
-    // The current directory is used as the boot up directory.
-    // It is set to the internal flash filesystem by default.
-    MP_STATE_PORT(vfs_cur) = vfs;
-
     return true;
 }
 #endif
@@ -616,7 +599,7 @@ soft_reset:
     // if an SD card is present then mount it on /sd/
     if (sdcard_is_present()) {
         // if there is a file in the flash called "SKIPSD", then we don't mount the SD card
-        if (!mounted_flash || f_stat(&fs_user_mount_flash.fatfs, "/SKIPSD", NULL) != FR_OK) {
+        if (!mounted_flash || mp_vfs_import_stat("SKIPSD") == MP_IMPORT_STAT_FILE) {
             mounted_sdcard = init_sdcard_fs();
         }
     }

ports/stm32/storage.c

@@ -234,7 +234,7 @@ mp_uint_t storage_write_blocks(const uint8_t *src, uint32_t block_num, uint32_t
 // Expose the flash as an object with the block protocol.
 
 // there is a singleton Flash object
-STATIC const mp_obj_base_t pyb_flash_obj = {&pyb_flash_type};
+const mp_obj_base_t pyb_flash_obj = {&pyb_flash_type};
 
 STATIC mp_obj_t pyb_flash_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
     // check arguments

ports/stm32/storage.h

@@ -63,6 +63,7 @@ int spi_bdev_readblocks(spi_bdev_t *bdev, uint8_t *dest, uint32_t block_num, uin
 int spi_bdev_writeblocks(spi_bdev_t *bdev, const uint8_t *src, uint32_t block_num, uint32_t num_blocks);
 
 extern const struct _mp_obj_type_t pyb_flash_type;
+extern const struct _mp_obj_base_t pyb_flash_obj;
 
 struct _fs_user_mount_t;
 void pyb_flash_init_vfs(struct _fs_user_mount_t *vfs);