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docs/library/os.rst: Clarify littlefs requirements for block erase.

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Peter Hinch 2021-09-07 07:56:26 +01:00 committed by Damien George
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@ -314,6 +314,12 @@ that the block device supports the extended interface.
``ioctl(6, ...)`` must also be intercepted. The need for others is ``ioctl(6, ...)`` must also be intercepted. The need for others is
hardware dependent. 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``. Unless otherwise stated ``ioctl(op, arg)`` can return ``None``.
Consequently an implementation can ignore unused values of ``op``. Where Consequently an implementation can ignore unused values of ``op``. Where
``op`` is intercepted, the return value for operations 4 and 5 are as ``op`` is intercepted, the return value for operations 4 and 5 are as