extmod/vfs_lfs: Add mtime support to littlefs files.

This commit adds support for modification time of files on littlefs v2
filesystems, using file attributes.  For some background see issue #6114.

Features/properties of this implementation:
- Only supported on littlefs2 (not littlefs1).
- Uses littlefs2's general file attributes to store the timestamp.
- The timestamp is 64-bits and stores nanoseconds since 1970/1/1 (if the
  range to the year 2554 is not enough then additional bits can be added to
  this timestamp by adding another file attribute).
- mtime is enabled by default but can be disabled in the constructor, eg:
  uos.mount(uos.VfsLfs2(bdev, mtime=False), '/flash')
- It's fully backwards compatible, existing littlefs2 filesystems will work
  without reformatting and timestamps will be added transparently to
  existing files (once they are opened for writing).
- Files without timestamps will open correctly, and stat will just return 0
  for their timestamp.
- mtime can be disabled or enabled each mount time and timestamps will only
  be updated if mtime is enabled (otherwise they will be untouched).

Signed-off-by: Damien George <damien@micropython.org>

1 files changed, 9 insertions, 4 deletions

diff --git a/tests/extmod/vfs_lfs.py b/tests/extmod/vfs_lfs.py
index 609d9f949..8e56400df 100644
--- a/tests/extmod/vfs_lfs.py
+++ b/tests/extmod/vfs_lfs.py
@@ -35,6 +35,11 @@ class RAMBlockDevice:
             return 0
 
 
+def print_stat(st, print_size=True):
+    # don't print times (just check that they have the correct type)
+    print(st[:6], st[6] if print_size else -1, type(st[7]), type(st[8]), type(st[9]))
+
+
 def test(bdev, vfs_class):
     print("test", vfs_class)
 
@@ -69,10 +74,10 @@ def test(bdev, vfs_class):
     vfs.mkdir("testdir")
 
     # stat a file
-    print(vfs.stat("test"))
+    print_stat(vfs.stat("test"))
 
     # stat a dir (size seems to vary on LFS2 so don't print that)
-    print(vfs.stat("testdir")[:6])
+    print_stat(vfs.stat("testdir"), False)
 
     # read
     with vfs.open("test", "r") as f:
@@ -112,8 +117,8 @@ def test(bdev, vfs_class):
 
     # create file in directory to make sure paths are relative
     vfs.open("test2", "w").close()
-    print(vfs.stat("test2"))
-    print(vfs.stat("/testdir/test2"))
+    print_stat(vfs.stat("test2"))
+    print_stat(vfs.stat("/testdir/test2"))
     vfs.remove("test2")
 
     # chdir back to root and remove testdir