39 lines
1.5 KiB
ReStructuredText
39 lines
1.5 KiB
ReStructuredText
.. _async_notification:
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Asynchronous Notification APIs
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##############################
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Zephyr APIs often include :ref:`api_term_async` functions where an
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operation is initiated and the application needs to be informed when it
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completes, and whether it succeeded. Using :cpp:func:`k_poll()` is
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often a good method, but some application architectures may be more
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suited to a callback notification, and operations like enabling clocks
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and power rails may need to be invoked before kernel functions are
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available so a busy-wait for completion may be needed.
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This API is intended to be embedded within specific subsystems such as
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:ref:`resource_mgmt_onoff` and other APIs that support async
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transactions. The subsystem wrappers are responsible for extracting
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operation-specific data from requests that include a notification
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element, and for invoking callbacks with the parameters required by the
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API.
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A limitation is that this API is not suitable for :ref:`syscalls`
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because:
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* :c:type:`sys_notify` is not a kernel object;
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* copying the notification content from userspace will break use of
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:c:macro:`CONTAINER_OF` in the implementing function;
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* neither the spin-wait nor callback notification methods can be
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accepted from userspace callers.
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Where a notification is required for an asynchronous operation invoked
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from a user mode thread the subsystem or driver should provide a syscall
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API that uses :c:type:`k_poll_signal` for notification.
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API Reference
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*************
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.. doxygengroup:: sys_notify_apis
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:project: Zephyr
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