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>

1 files changed, 73 insertions, 0 deletions

diff --git a/ports/zephyr/modules/_boot.py b/ports/zephyr/modules/_boot.py
new file mode 100644
index 000000000..5af302fad
--- /dev/null
+++ b/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