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Diffstat (limited to 'docs/library/os.rst')
| -rw-r--r-- | docs/library/os.rst | 184 |
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diff --git a/docs/library/os.rst b/docs/library/os.rst index 27a7d2d44a..710875e34c 100644 --- a/docs/library/os.rst +++ b/docs/library/os.rst @@ -136,192 +136,30 @@ Terminal redirection and duplication Filesystem mounting ------------------- -Some ports provide a Virtual Filesystem (VFS) and the ability to mount multiple -"real" filesystems within this VFS. Filesystem objects can be mounted at either -the root of the VFS, or at a subdirectory that lives in the root. This allows -dynamic and flexible configuration of the filesystem that is seen by Python -programs. Ports that have this functionality provide the :func:`mount` and -:func:`umount` functions, and possibly various filesystem implementations -represented by VFS classes. +The following functions and classes have been moved to the :mod:`vfs` module. +They are provided in this module only for backwards compatibility and will be +removed in version 2 of MicroPython. .. function:: mount(fsobj, mount_point, *, readonly) - Mount the filesystem object *fsobj* at the location in the VFS given by the - *mount_point* string. *fsobj* can be a a VFS object that has a ``mount()`` - method, or a block device. If it's a block device then the filesystem type - is automatically detected (an exception is raised if no filesystem was - recognised). *mount_point* may be ``'/'`` to mount *fsobj* at the root, - or ``'/<name>'`` to mount it at a subdirectory under the root. - - If *readonly* is ``True`` then the filesystem is mounted read-only. - - During the mount process the method ``mount()`` is called on the filesystem - object. - - Will raise ``OSError(EPERM)`` if *mount_point* is already mounted. + See `vfs.mount`. .. function:: umount(mount_point) - Unmount a filesystem. *mount_point* can be a string naming the mount location, - or a previously-mounted filesystem object. During the unmount process the - method ``umount()`` is called on the filesystem object. - - Will raise ``OSError(EINVAL)`` if *mount_point* is not found. + See `vfs.umount`. .. class:: VfsFat(block_dev) - Create a filesystem object that uses the FAT filesystem format. Storage of - the FAT filesystem is provided by *block_dev*. - Objects created by this constructor can be mounted using :func:`mount`. - - .. staticmethod:: mkfs(block_dev) - - Build a FAT filesystem on *block_dev*. + See `vfs.VfsFat`. .. class:: VfsLfs1(block_dev, readsize=32, progsize=32, lookahead=32) - Create a filesystem object that uses the `littlefs v1 filesystem format`_. - Storage of the littlefs filesystem is provided by *block_dev*, which must - support the :ref:`extended interface <block-device-interface>`. - Objects created by this constructor can be mounted using :func:`mount`. - - See :ref:`filesystem` for more information. - - .. staticmethod:: mkfs(block_dev, readsize=32, progsize=32, lookahead=32) - - Build a Lfs1 filesystem on *block_dev*. - - .. note:: There are reports of littlefs v1 failing in certain situations, - for details see `littlefs issue 347`_. + See `vfs.VfsLfs1`. .. class:: VfsLfs2(block_dev, readsize=32, progsize=32, lookahead=32, mtime=True) - Create a filesystem object that uses the `littlefs v2 filesystem format`_. - Storage of the littlefs filesystem is provided by *block_dev*, which must - support the :ref:`extended interface <block-device-interface>`. - Objects created by this constructor can be mounted using :func:`mount`. + See `vfs.VfsLfs2`. + +.. class:: VfsPosix(root=None) - The *mtime* argument enables modification timestamps for files, stored using - littlefs attributes. This option can be disabled or enabled differently each - mount time and timestamps will only be added or updated if *mtime* is enabled, - otherwise the timestamps will remain untouched. Littlefs v2 filesystems without - timestamps will work without reformatting and timestamps will be added - transparently to existing files once they are opened for writing. When *mtime* - is enabled `os.stat` on files without timestamps will return 0 for the timestamp. - - See :ref:`filesystem` for more information. - - .. staticmethod:: mkfs(block_dev, readsize=32, progsize=32, lookahead=32) - - Build a Lfs2 filesystem on *block_dev*. - - .. note:: There are reports of littlefs v2 failing in certain situations, - for details see `littlefs issue 295`_. - -.. _littlefs v1 filesystem format: https://github.com/ARMmbed/littlefs/tree/v1 -.. _littlefs v2 filesystem format: https://github.com/ARMmbed/littlefs -.. _littlefs issue 295: https://github.com/ARMmbed/littlefs/issues/295 -.. _littlefs issue 347: https://github.com/ARMmbed/littlefs/issues/347 - -Block devices -------------- - -A block device is an object which implements the block protocol. This enables a -device to support MicroPython filesystems. The physical hardware is represented -by a user defined class. The :class:`AbstractBlockDev` class is a template for -the design of such a class: MicroPython does not actually provide that class, -but an actual block device class must implement the methods described below. - -A concrete implementation of this class will usually allow access to the -memory-like functionality of a piece of hardware (like flash memory). A block -device can be formatted to any supported filesystem and mounted using ``os`` -methods. - -See :ref:`filesystem` for example implementations of block devices using the -two variants of the block protocol described below. - -.. _block-device-interface: - -Simple and extended interface -............................. - -There are two compatible signatures for the ``readblocks`` and ``writeblocks`` -methods (see below), in order to support a variety of use cases. A given block -device may implement one form or the other, or both at the same time. The second -form (with the offset parameter) is referred to as the "extended interface". - -Some filesystems (such as littlefs) that require more control over write -operations, for example writing to sub-block regions without erasing, may require -that the block device supports the extended interface. - -.. class:: AbstractBlockDev(...) - - Construct a block device object. The parameters to the constructor are - dependent on the specific block device. - - .. method:: readblocks(block_num, buf) - readblocks(block_num, buf, offset) - - The first form reads aligned, multiples of blocks. - Starting at the block given by the index *block_num*, read blocks from - the device into *buf* (an array of bytes). - The number of blocks to read is given by the length of *buf*, - which will be a multiple of the block size. - - The second form allows reading at arbitrary locations within a block, - and arbitrary lengths. - Starting at block index *block_num*, and byte offset within that block - of *offset*, read bytes from the device into *buf* (an array of bytes). - The number of bytes to read is given by the length of *buf*. - - .. method:: writeblocks(block_num, buf) - writeblocks(block_num, buf, offset) - - The first form writes aligned, multiples of blocks, and requires that the - blocks that are written to be first erased (if necessary) by this method. - Starting at the block given by the index *block_num*, write blocks from - *buf* (an array of bytes) to the device. - The number of blocks to write is given by the length of *buf*, - which will be a multiple of the block size. - - The second form allows writing at arbitrary locations within a block, - and arbitrary lengths. Only the bytes being written should be changed, - and the caller of this method must ensure that the relevant blocks are - erased via a prior ``ioctl`` call. - Starting at block index *block_num*, and byte offset within that block - of *offset*, write bytes from *buf* (an array of bytes) to the device. - The number of bytes to write is given by the length of *buf*. - - Note that implementations must never implicitly erase blocks if the offset - argument is specified, even if it is zero. - - .. method:: ioctl(op, arg) - - Control the block device and query its parameters. The operation to - perform is given by *op* which is one of the following integers: - - - 1 -- initialise the device (*arg* is unused) - - 2 -- shutdown the device (*arg* is unused) - - 3 -- sync the device (*arg* is unused) - - 4 -- get a count of the number of blocks, should return an integer - (*arg* is unused) - - 5 -- get the number of bytes in a block, should return an integer, - or ``None`` in which case the default value of 512 is used - (*arg* is unused) - - 6 -- erase a block, *arg* is the block number to erase - - As a minimum ``ioctl(4, ...)`` must be intercepted; for littlefs - ``ioctl(6, ...)`` must also be intercepted. The need for others is - hardware dependent. - - Prior to any call to ``writeblocks(block, ...)`` littlefs issues - ``ioctl(6, block)``. This enables a device driver to erase the block - prior to a write if the hardware requires it. Alternatively a driver - might intercept ``ioctl(6, block)`` and return 0 (success). In this case - the driver assumes responsibility for detecting the need for erasure. - - Unless otherwise stated ``ioctl(op, arg)`` can return ``None``. - Consequently an implementation can ignore unused values of ``op``. Where - ``op`` is intercepted, the return value for operations 4 and 5 are as - detailed above. Other operations should return 0 on success and non-zero - for failure, with the value returned being an ``OSError`` errno code. + See `vfs.VfsPosix`. |