The superblock for littlefs is in block 0 and 1, but block 0 may be erased
or partially written, so block 1 must be checked if block 0 does not have a
valid littlefs superblock in it.
Prior to this commit, the mount of a block device which auto-detected the
filysystem type would fail for littlefs if block 0 did not contain a valid
superblock. That is now fixed.
Signed-off-by: Damien George <damien@micropython.org>
This commit prevents uos.mount() from raising an AttributeError.
vfs_autodetect() is supposed to return an object that has a "mount" method,
so if no filesystem is found it should raise an OSError(ENODEV) and not
return the bdev itself which has no "mount" method.
Prior to this commit, uos.chdir('/') followed by uos.stat('noexist') would
succeed that stat even though the entry did not exist (some other functions
like listdir would have similar issues). This is because, if the current
directory was the root and the path was relative, mp_vfs_lookup_path would
return success for bad paths.
Signed-off-by: Damien George <damien@micropython.org>
Following other C-level protocols, this VFS protocol is added to help
abstract away implementation details of the underlying VFS in an efficient
way. As a starting point, the import_stat function is put into this
protocol so that the VFS sub-system does not need to know about every VFS
implementation in order to do an efficient stat for importing files.
In the future it might be worth adding other functions to this protocol.
VLAs can be expensive on stack usage due to stack alignment requirements,
and also the fact that extra local variables are needed to track the
dynamic size of the stack. So using fixed-size arrays when possible can
help to reduce code size and stack usage.
In this particular case, the maximum value of n_args in the VLA is 2 and so
it's more efficient to just allocate this array with a fixed size. This
reduces code size by around 30 bytes on Thumb2 and Xtensa archs. It also
reduces total stack usage of the function: on Thumb2 the usage with VLA is
between 40 and 48 bytes, which is reduced to 32; on Xtensa, VLA usage is
between 64 and 80 bytes, reduced to 32; on x86-64 it's at least 88 bytes
reduced to 80.
Header files that are considered internal to the py core and should not
normally be included directly are:
py/nlr.h - internal nlr configuration and declarations
py/bc0.h - contains bytecode macro definitions
py/runtime0.h - contains basic runtime enums
Instead, the top-level header files to include are one of:
py/obj.h - includes runtime0.h and defines everything to use the
mp_obj_t type
py/runtime.h - includes mpstate.h and hence nlr.h, obj.h, runtime0.h,
and defines everything to use the general runtime support functions
Additional, specific headers (eg py/objlist.h) can be included if needed.
This patch allows mounting of VFS objects right at the root directory, eg
os.mount(vfs, '/'). It still allows VFS's to be mounted at a path within
the root, eg os.mount(vfs, '/flash'), and such mount points will override
any paths within a VFS that is mounted at the root.
For example, if the current directory is the root dir then this patch
allows one to do uos.listdir('mnt'), where 'mnt' is a valid mount point.
Previous to this patch such a thing would not work, on needed to do
uos.listdir('/mnt') instead.
If the mounted object doesn't have a "mount" method then assume it's a
block device and try to detect the filesystem. Since we currently only
support FAT filesystems, the behaviour is to just try and create a VfsFat
object automatically, using the given block device.
This provides mp_vfs_XXX functions (eg mount, open, listdir) which are
agnostic to the underlying filesystem type, and just require an object with
the relevant filesystem-like methods (eg .mount, .open, .listidr) which can
then be mounted.
These mp_vfs_XXX functions would typically be used by a port to implement
the "uos" module, and mp_vfs_open would be the builtin open function.
This feature is controlled by MICROPY_VFS, disabled by default.
Damien George
Oliver Joos
Damien George
Tom Collins