zephyr: Mount all disks and flash partition, formatting if necessary.

Existing C code in `main.c` only mounts a flash filesystem if one exists,
and doesn't do anything if the 'storage' partition is not formatted.

This commit moves the mounting logic from `main.c` to frozen code using
`modules/_boot.py` and adds the formatting of a previously unformatted
partition if the mount fails.

Every available disk (in the newly added `DiskAccess.disks` tuple) will be
mounted on separate mount points (if they're formatted), and the 'storage'
flash partition (if any) will be mounted on /flash (and will be formatted
as LFS2 if necessary).

Also, `sys.path` will be updated with appropriate 'lib' subdirectories for
each mounted filesystem.

The current working directory will be changed to the last `DiskAccess.disk`
mounted, or to /flash if no disks were mounted.

Then `boot.py` and `main.py` will be executed from the current working
directory if they exist.

Thanks to @VynDragon for the logic in `zephyr/zephyr_storage.c`.

Signed-off-by: Ned Konz <ned@metamagix.tech>

docs/zephyr/quickref.rst

@@ -135,11 +135,14 @@ the ``io-channels`` property containing all the ADC channels)::
 Disk Access
 -----------
 
-Use the :ref:`zephyr.DiskAccess <zephyr.DiskAccess>` class to support filesystem::
+Storage devices such as SD cards are automatically mounted at startup (e.g., at ``/sd``).
+For manual mounting, use the :ref:`zephyr.DiskAccess <zephyr.DiskAccess>` class::
 
     import vfs
     from zephyr import DiskAccess
 
+    print(DiskAccess.disks)             # list available disk names, e.g., ('SDHC',)
+
     block_dev = DiskAccess('SDHC')      # create a block device object for an SD card
     vfs.VfsFat.mkfs(block_dev)          # create FAT filesystem object using the disk storage block
     vfs.mount(block_dev, '/sd')         # mount the filesystem at the SD card subdirectory
@@ -152,12 +155,15 @@ Use the :ref:`zephyr.DiskAccess <zephyr.DiskAccess>` class to support filesystem
 Flash Area
 ----------
 
-Use the :ref:`zephyr.FlashArea <zephyr.FlashArea>` class to support filesystem::
+Flash storage is automatically mounted at ``/flash`` at startup with automatic filesystem creation.
+For manual mounting, use the :ref:`zephyr.FlashArea <zephyr.FlashArea>` class::
 
     import vfs
     from zephyr import FlashArea
 
-    block_dev = FlashArea(4, 4096)      # creates a block device object in the frdm-k64f flash scratch partition
+    print(FlashArea.areas)              # list available areas, e.g., {'storage': 1, 'scratch': 4}
+
+    block_dev = FlashArea(FlashArea.areas['scratch'], 4096)  # creates a block device object using the scratch partition
     vfs.VfsLfs2.mkfs(block_dev)         # create filesystem in lfs2 format using the flash block device
     vfs.mount(block_dev, '/flash')      # mount the filesystem at the flash subdirectory
 
@@ -166,8 +172,6 @@ Use the :ref:`zephyr.FlashArea <zephyr.FlashArea>` class to support filesystem::
         f.write('Hello world')                  # write to the file
     print(open('/flash/hello.txt').read())      # print contents of the file
 
-The ``FlashAreas``' IDs that are available are listed in the FlashArea module, as ``ID_*``.
-
 Sensor
 ------
 

docs/zephyr/tutorial/storage.rst

@@ -8,6 +8,27 @@ Zephyr DiskAccess or FlashArea (flash map) APIs depending on which the board sup
 
 See `vfs Filesystem Mounting <https://docs.micropython.org/en/latest/library/vfs.html?highlight=vfs#filesystem-mounting>`_.
 
+Automatic Filesystem Mounting
+------------------------------
+
+MicroPython on Zephyr automatically attempts to mount available storage at startup:
+
+1. **Flash storage** (if available): Automatically mounted at ``/flash`` using the
+   littlefs2 filesystem. If the filesystem doesn't exist, it will be created
+   automatically.
+
+2. **Disk storage** (such as SD cards): Automatically detected and mounted at
+   ``/<disk_name>`` (e.g., ``/sd`` for SD cards).
+
+3. **Working directory**: The working directory is set to the mounted disk if
+   available, otherwise to ``/flash`` if flash storage is available.
+
+4. **Module search path**: The ``sys.path`` is automatically updated to include
+   ``/<disk>/lib`` for each mounted disk and ``/flash/lib`` for flash storage.
+
+This automatic mounting is performed by the ``_boot.py`` module at startup. For most
+use cases, you don't need to manually mount filesystems.
+
 Disk Access
 -----------
 
@@ -19,17 +40,26 @@ For use with SD card controllers, SD cards must be present at boot & not removed
 be auto detected and initialized by filesystem at boot. Use the disk driver interface and a
 file system to access SD cards via disk access (see below).
 
+The available disk names can be accessed via the ``DiskAccess.disks`` attribute, which contains
+a tuple of available disk names (e.g., ``('SDHC',)`` or ``('SD',)``).
+
 Example usage of FatFS with an SD card on the mimxrt1050_evk board::
 
     import vfs
     from zephyr import DiskAccess
-    bdev = zephyr.DiskAccess('SDHC')        # create block device object using DiskAccess
+
+    # List available disks
+    print(DiskAccess.disks)                 # prints available disk names, e.g., ('SDHC',)
+
+    bdev = DiskAccess('SDHC')               # create block device object using DiskAccess
     vfs.VfsFat.mkfs(bdev)                   # create FAT filesystem object using the disk storage block
     vfs.mount(bdev, '/sd')                  # mount the filesystem at the SD card subdirectory
     with open('/sd/hello.txt','w') as f:    # open a new file in the directory
         f.write('Hello world')              # write to the file
     print(open('/sd/hello.txt').read())     # print contents of the file
 
+Note: In most cases, disks are automatically mounted at startup and manual mounting is not necessary.
+
 
 Flash Area
 ----------
@@ -41,16 +71,26 @@ API is recommended (see below).
 This class uses `Zephyr Flash map API <https://docs.zephyrproject.org/latest/reference/storage/flash_map/flash_map.html#>`_ and
 implements the `vfs.AbstractBlockDev` protocol.
 
+The available flash area names can be accessed via the ``FlashArea.areas`` dictionary, which maps partition
+labels to their IDs (e.g., ``{'storage': 1, 'scratch': 4}``).
+
 Example usage with the internal flash on the reel_board or the rv32m1_vega_ri5cy board::
 
     import vfs
     from zephyr import FlashArea
-    bdev = FlashArea(FlashArea.STORAGE, 4096)   # create block device object using FlashArea
-    vfs.VfsLfs2.mkfs(bdev)                      # create Little filesystem object using the flash area block
-    vfs.mount(bdev, '/flash')                   # mount the filesystem at the flash storage subdirectory
-    with open('/flash/hello.txt','w') as f:     # open a new file in the directory
-        f.write('Hello world')                  # write to the file
-    print(open('/flash/hello.txt').read())      # print contents of the file
+
+    # List available flash areas
+    print(FlashArea.areas)                          # prints available areas, e.g., {'storage': 1, 'scratch': 4}
+
+    bdev = FlashArea(FlashArea.areas['storage'], 4096)   # create block device object using FlashArea
+    vfs.VfsLfs2.mkfs(bdev)                               # create Little filesystem object using the flash area block
+    vfs.mount(bdev, '/flash')                            # mount the filesystem at the flash storage subdirectory
+    with open('/flash/hello.txt','w') as f:              # open a new file in the directory
+        f.write('Hello world')                           # write to the file
+    print(open('/flash/hello.txt').read())               # print contents of the file
+
+Note: In most cases, the flash storage partition is automatically mounted at ``/flash`` at startup with
+automatic filesystem creation if needed, so manual mounting is not necessary.
 
 For boards such as the frdm_k64f in which the MicroPython application spills into the default flash storage
-partition, use the scratch partition by replacing ``FlashArea.STORAGE`` with the integer value 4.
+partition, use the scratch partition by replacing ``'storage'`` with ``'scratch'``.

ports/zephyr/Kconfig

@@ -43,6 +43,7 @@ config MICROPY_VFS_LFS2
 
 config MICROPY_FROZEN_MODULES
 	bool "Enable Frozen Modules"
+	default y if FLASH_MAP || DISK_ACCESS
 
 config MICROPY_FROZEN_MANIFEST
 	string "Path to Frozen Modules manifest.py"

ports/zephyr/main.c

@@ -94,39 +94,6 @@ void init_zephyr(void) {
     #endif
 }
 
-#if MICROPY_VFS
-static void vfs_init(void) {
-    mp_obj_t bdev = NULL;
-    mp_obj_t mount_point;
-    const char *mount_point_str = NULL;
-    qstr path_lib_qstr = MP_QSTRnull;
-    int ret = 0;
-
-    #ifdef CONFIG_DISK_DRIVER_SDMMC
-    #if KERNEL_VERSION_NUMBER >= ZEPHYR_VERSION(4, 0, 0)
-    mp_obj_t args[] = { mp_obj_new_str_from_cstr(DT_PROP(DT_INST(0, zephyr_sdmmc_disk), disk_name)) };
-    #else
-    mp_obj_t args[] = { mp_obj_new_str_from_cstr(CONFIG_SDMMC_VOLUME_NAME) };
-    #endif
-    bdev = MP_OBJ_TYPE_GET_SLOT(&zephyr_disk_access_type, make_new)(&zephyr_disk_access_type, ARRAY_SIZE(args), 0, args);
-    mount_point_str = "/sd";
-    path_lib_qstr = MP_QSTR__slash_sd_slash_lib;
-    #elif defined(CONFIG_FLASH_MAP) && FIXED_PARTITION_EXISTS(storage_partition)
-    mp_obj_t args[] = { MP_OBJ_NEW_SMALL_INT(FIXED_PARTITION_ID(storage_partition)), MP_OBJ_NEW_SMALL_INT(4096) };
-    bdev = MP_OBJ_TYPE_GET_SLOT(&zephyr_flash_area_type, make_new)(&zephyr_flash_area_type, ARRAY_SIZE(args), 0, args);
-    mount_point_str = "/flash";
-    path_lib_qstr = MP_QSTR__slash_flash_slash_lib;
-    #endif
-
-    if ((bdev != NULL)) {
-        mount_point = mp_obj_new_str_from_cstr(mount_point_str);
-        ret = mp_vfs_mount_and_chdir_protected(bdev, mount_point);
-        mp_obj_list_append(mp_sys_path, MP_OBJ_NEW_QSTR(path_lib_qstr));
-        // TODO: if this failed, make a new file system and try to mount again
-    }
-}
-#endif // MICROPY_VFS
-
 int real_main(void) {
     #if MICROPY_PY_THREAD
     struct k_thread *z_thread = (struct k_thread *)k_current_get();
@@ -151,10 +118,12 @@ soft_reset:
     mp_usbd_init();
     #endif
 
-    #if MICROPY_VFS
-    vfs_init();
+    #if MICROPY_VFS && MICROPY_MODULE_FROZEN_MPY
+    // Mount and/or create the filesystem
+    pyexec_frozen_module("_boot.py", false);
     #endif
 
+
     #if MICROPY_MODULE_FROZEN || MICROPY_VFS
     // Execute user scripts.
     int ret = pyexec_file_if_exists("boot.py");
@@ -181,7 +150,7 @@ soft_reset:
         }
     }
 
-    #if MICROPY_MODULE_FROZEN || MICROPY_VFS
+    #if MICROPY_MODULE_FROZEN_MPY || MICROPY_VFS
 soft_reset_exit:
     #endif
 

ports/zephyr/modules/_boot.py

@@ -0,0 +1,73 @@
+# ruff: noqa: F821
+import sys
+import os
+from micropython import const
+import vfs  # vfs is always available
+import zephyr
+
+# FlashArea depends on CONFIG_FLASH_MAP
+FlashArea = getattr(zephyr, "FlashArea", None)
+
+# DiskAccess depends on CONFIG_DISK_ACCESS
+DiskAccess = getattr(zephyr, "DiskAccess", None)
+
+_FLASH = const("/flash")
+_FLASH_LIB = const("/flash/lib")
+_STORAGE_KEY = const("storage")
+_FLASH_EXISTS = False
+
+
+def create_flash_partition():
+    """Create an LFS2 filesystem on the partition labeled storage
+    and mount it on /flash.
+    Return True if successful, False otherwise.
+    """
+    if _STORAGE_KEY in FlashArea.areas:
+        # TODO: get the erase block size from DTS instead of 4K.
+        bdev = FlashArea(FlashArea.areas[_STORAGE_KEY], 4096)
+        retval = True
+        try:
+            vfs.mount(bdev, _FLASH)
+        except OSError:
+            try:
+                vfs.VfsLfs2.mkfs(bdev)
+                vfs.mount(bdev, _FLASH)
+            except OSError:
+                print("Error formatting flash partition")
+                retval = False
+        return retval
+    return False
+
+
+def mount_all_disks():
+    """Now mount all the DiskAreas (if any)."""
+    retval = False
+    for da_name in DiskAccess.disks:
+        mount_name = f"/{da_name.lower()}"
+        da = DiskAccess(da_name)
+        try:
+            vfs.mount(da, mount_name)
+            sys.path.append(f"{mount_name}/lib")
+            os.chdir(mount_name)
+            retval = True
+        except OSError as e:
+            print(f"Error mounting {da_name}: {e}")
+    return retval
+
+
+if FlashArea and create_flash_partition():
+    _FLASH_EXISTS = True
+
+# Prefer disks to /flash
+if not (DiskAccess and mount_all_disks()):
+    if _FLASH_EXISTS:
+        os.chdir(_FLASH)
+
+# Place /flash/lib last on sys.path
+if _FLASH_EXISTS:
+    sys.path.append(_FLASH_LIB)
+
+# Cleanup globals for boot.py/main.py
+del FlashArea, DiskAccess, zephyr
+del sys, vfs, os, const
+del create_flash_partition, mount_all_disks, _FLASH_EXISTS

ports/zephyr/zephyr_storage.c

@@ -40,6 +40,11 @@
 #endif
 
 #ifdef CONFIG_DISK_ACCESS
+
+#define DISK_DEFINE_NAME(part) CONCAT(MP_QSTR_, DT_STRING_TOKEN(part, disk_name))
+
+#define FOREACH_DISK(n) MP_ROM_QSTR(DISK_DEFINE_NAME(n)),
+
 typedef struct _zephyr_disk_access_obj_t {
     mp_obj_base_t base;
     const char *pdrv;
@@ -121,10 +126,43 @@ static mp_obj_t zephyr_disk_access_ioctl(mp_obj_t self_in, mp_obj_t cmd_in, mp_o
 }
 static MP_DEFINE_CONST_FUN_OBJ_3(zephyr_disk_access_ioctl_obj, zephyr_disk_access_ioctl);
 
+static const mp_rom_obj_tuple_t zephyr_disks_tuple = {
+    .base = {.type = &mp_type_tuple},
+    .items = {
+        #ifdef CONFIG_DISK_DRIVER_SDMMC
+        DT_FOREACH_STATUS_OKAY(zephyr_sdmmc_disk, FOREACH_DISK)
+        #endif
+        #ifdef CONFIG_DISK_DRIVER_MMC
+        DT_FOREACH_STATUS_OKAY(zephyr_mmc_disk, FOREACH_DISK)
+        #endif
+        #ifdef CONFIG_DISK_DRIVER_FLASH
+        DT_FOREACH_STATUS_OKAY(zephyr_flash_disk, FOREACH_DISK)
+        #endif
+        #ifdef CONFIG_DISK_DRIVER_RAM
+        DT_FOREACH_STATUS_OKAY(zephyr_ram_disk, FOREACH_DISK)
+        #endif
+    },
+    .len = MP_ARRAY_SIZE((mp_rom_obj_t []) {
+        #ifdef CONFIG_DISK_DRIVER_SDMMC
+        DT_FOREACH_STATUS_OKAY(zephyr_sdmmc_disk, FOREACH_DISK)
+        #endif
+        #ifdef CONFIG_DISK_DRIVER_MMC
+        DT_FOREACH_STATUS_OKAY(zephyr_mmc_disk, FOREACH_DISK)
+        #endif
+        #ifdef CONFIG_DISK_DRIVER_FLASH
+        DT_FOREACH_STATUS_OKAY(zephyr_flash_disk, FOREACH_DISK)
+        #endif
+        #ifdef CONFIG_DISK_DRIVER_RAM
+        DT_FOREACH_STATUS_OKAY(zephyr_ram_disk, FOREACH_DISK)
+        #endif
+    })
+};
+
 static const mp_rom_map_elem_t zephyr_disk_access_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_readblocks), MP_ROM_PTR(&zephyr_disk_access_readblocks_obj) },
     { MP_ROM_QSTR(MP_QSTR_writeblocks), MP_ROM_PTR(&zephyr_disk_access_writeblocks_obj) },
     { MP_ROM_QSTR(MP_QSTR_ioctl), MP_ROM_PTR(&zephyr_disk_access_ioctl_obj) },
+    { MP_ROM_QSTR(MP_QSTR_disks), MP_ROM_PTR(&zephyr_disks_tuple) },
 };
 static MP_DEFINE_CONST_DICT(zephyr_disk_access_locals_dict, zephyr_disk_access_locals_dict_table);
 
@@ -140,8 +178,8 @@ MP_DEFINE_CONST_OBJ_TYPE(
 
 #ifdef CONFIG_FLASH_MAP
 
-#define FLASH_AREA_DEFINE_LABEL(part) CONCAT(MP_QSTR_ID_, DT_STRING_TOKEN(part, label))
-#define FLASH_AREA_DEFINE_NB(part) CONCAT(MP_QSTR_ID_, DT_FIXED_PARTITION_ID(part))
+#define FLASH_AREA_DEFINE_LABEL(part) CONCAT(MP_QSTR_, DT_STRING_TOKEN(part, label))
+#define FLASH_AREA_DEFINE_NB(part) CONCAT(MP_QSTR_, DT_FIXED_PARTITION_ID(part))
 
 #define FLASH_AREA_DEFINE_GETNAME(part) COND_CODE_1(DT_NODE_HAS_PROP(part, label), \
     (FLASH_AREA_DEFINE_LABEL(part)), (FLASH_AREA_DEFINE_NB(part)))
@@ -254,12 +292,17 @@ static mp_obj_t zephyr_flash_area_ioctl(mp_obj_t self_in, mp_obj_t cmd_in, mp_ob
 }
 static MP_DEFINE_CONST_FUN_OBJ_3(zephyr_flash_area_ioctl_obj, zephyr_flash_area_ioctl);
 
+static const mp_rom_map_elem_t zephyr_flash_areas_table[] = {
+    /* Generate list of partition IDs from Zephyr Devicetree */
+    DT_FOREACH_STATUS_OKAY(fixed_partitions, FOREACH_PARTITION)
+};
+static MP_DEFINE_CONST_DICT(zephyr_flash_areas_dict, zephyr_flash_areas_table);
+
 static const mp_rom_map_elem_t zephyr_flash_area_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_readblocks), MP_ROM_PTR(&zephyr_flash_area_readblocks_obj) },
     { MP_ROM_QSTR(MP_QSTR_writeblocks), MP_ROM_PTR(&zephyr_flash_area_writeblocks_obj) },
     { MP_ROM_QSTR(MP_QSTR_ioctl), MP_ROM_PTR(&zephyr_flash_area_ioctl_obj) },
-    /* Generate list of partition IDs from Zephyr Devicetree */
-    DT_FOREACH_STATUS_OKAY(fixed_partitions, FOREACH_PARTITION)
+    { MP_ROM_QSTR(MP_QSTR_areas), MP_ROM_PTR(&zephyr_flash_areas_dict) },
 };
 static MP_DEFINE_CONST_DICT(zephyr_flash_area_locals_dict, zephyr_flash_area_locals_dict_table);