64 lines
2.2 KiB
ReStructuredText
64 lines
2.2 KiB
ReStructuredText
.. _file_system_api:
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File Systems
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############
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Zephyr RTOS Virtual Filesystem Switch (VFS) allows applications to mount multiple
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file systems at different mount points (e.g., ``/fatfs`` and ``/lfs``). The
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mount point data structure contains all the necessary information required
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to instantiate, mount, and operate on a file system. The File system Switch
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decouples the applications from directly accessing an individual file system's
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specific API or internal functions by introducing file system registration
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mechanisms.
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In Zephyr, any file system implementation or library can be plugged into or
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pulled out through a file system registration API. Each file system
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implementation must have a globally unique integer identifier; use
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:c:macro:`FS_TYPE_EXTERNAL_BASE` to avoid clashes with in-tree identifiers.
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.. code-block:: c
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int fs_register(int type, const struct fs_file_system_t *fs);
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int fs_unregister(int type, const struct fs_file_system_t *fs);
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Zephyr RTOS supports multiple instances of a file system by making use of
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the mount point as the disk volume name, which is used by the file system library
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while formatting or mounting a disk.
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A file system is declared as:
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.. code-block:: c
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static struct fs_mount_t mp = {
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.type = FS_FATFS,
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.mnt_point = FATFS_MNTP,
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.fs_data = &fat_fs,
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};
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where
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- ``FS_FATFS`` is the file system type like FATFS or LittleFS.
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- ``FATFS_MNTP`` is the mount point where the file system will be mounted.
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- ``fat_fs`` is the file system data which will be used by fs_mount() API.
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Samples
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*******
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Samples for the VFS are mainly supplied in ``samples/subsys/fs``, although various examples of the
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VFS usage are provided as important functionalities in samples for different subsystems.
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Here is the list of samples worth looking at:
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- ``samples/subsys/fs/fat_fs`` is an example of FAT file system usage with SDHC media;
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- ``samples/subsys/shell/fs`` is an example of Shell fs subsystem, using internal flash partition
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formatted to LittleFS;
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- ``samples/subsys/usb/mass/`` example of USB Mass Storage device that uses FAT FS driver with RAM
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or SPI connected FLASH, or LittleFS in flash, depending on the sample configuration.
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API Reference
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*************
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.. doxygengroup:: file_system_api
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