41 lines
1.7 KiB
ReStructuredText
41 lines
1.7 KiB
ReStructuredText
====================
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Block Device Drivers
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====================
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Block device drivers have these properties:
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- ``include/nuttx/fs/fs.h``. All structures and APIs needed
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to work with block drivers are provided in this header file.
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- ``struct block_operations``. Each block device driver must
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implement an instance of ``struct block_operations``. That
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structure defines a call table with the following methods:
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- ``int register_blockdriver(const char *path, const struct block_operations *bops, mode_t mode, void *priv);``.
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Each block driver registers itself by calling
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``register_blockdriver()``, passing it the ``path`` where it
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will appear in the :ref:`pseudo file system <file_system_overview>` and
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it's initialized instance of ``struct block_operations``.
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- **User Access**. Users do not normally access block drivers
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directly, rather, they access block drivers indirectly through
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the ``mount()`` API. The ``mount()`` API binds a block driver
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instance with a file system and with a mountpoint. Then the
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user may use the block driver to access the file system on the
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underlying media. *Example*: See the ``cmd_mount()``
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implementation in ``apps/nshlib/nsh_fscmds.c``.
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- **Accessing a Character Driver as a Block Device**. See the
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loop device at ``drivers/loop.c``. *Example*: See the
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``cmd_losetup()`` implementation in
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``apps/nshlib/nsh_fscmds.c``.
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- **Accessing a Block Driver as Character Device**. See the
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Block-to-Character (BCH) conversion logic in ``drivers/bch/``.
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*Example*: See the ``cmd_dd()`` implementation in
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``apps/nshlib/nsh_ddcmd.c``.
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- **Examples**. ``drivers/loop.c``,
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``drivers/mmcsd/mmcsd_spi.c``, ``drivers/ramdisk.c``, etc.
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