77 lines
3.1 KiB
C
77 lines
3.1 KiB
C
// This file is part of the CircuitPython project: https://circuitpython.org
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//
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// SPDX-FileCopyrightText: Copyright (c) 2020 Jeff Epler for Adafruit Industries
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//
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// SPDX-License-Identifier: MIT
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#pragma once
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#include <stdbool.h>
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/** Background callbacks are a linked list of tasks to call in the background.
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*
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* Include a member of type `background_callback_t` inside an object
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* which needs to queue up background work, and zero-initialize it.
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*
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* To schedule the work, use background_callback_add, with fun as the
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* function to call and data pointing to the object itself.
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*
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* Next time background_callback_run_all() is called, the callback will
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* be run and removed from the linked list. Use `RUN_BACKGROUND_TASKS;` instead
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* of calling background_callback_run_all() directly.
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*
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* Queueing a task that is already queued does nothing. Unconditionally
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* re-queueing it from its own background task will cause it to run during the
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* very next background-tasks invocation, leading to a CircuitPython freeze, so
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* don't do that.
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*
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* background_callback_add can be called from interrupt context.
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*
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* If your work isn't triggered by an event, then it may be better implemented
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* using ticks, which runs tasks every millisecond or so. Ticks are enabled with
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* supervisor_enable_tick() and disabled with supervisor_disable_tick(). When
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* enabled, a timer will schedule a callback to supervisor_background_tick(),
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* which includes port_background_tick(), every millisecond.
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*/
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typedef void (*background_callback_fun)(void *data);
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typedef struct background_callback {
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background_callback_fun fun;
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void *data;
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struct background_callback *next;
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struct background_callback *prev;
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} background_callback_t;
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/* Add a background callback for which 'fun' and 'data' were previously set */
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void background_callback_add_core(background_callback_t *cb);
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/* Add a background callback to the given function with the given data. When
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* the callback involves an object on the GC heap, the 'data' must be a pointer
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* to that object itself, not an internal pointer. Otherwise, it can be the
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* case that no other references to the object itself survive, and the object
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* becomes garbage collected while an outstanding background callback still
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* exists.
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*/
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void background_callback_add(background_callback_t *cb, background_callback_fun fun, void *data);
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/* Run all background callbacks. Normally, this is done by the supervisor
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* whenever the list is non-empty */
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void background_callback_run_all(void);
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/* True when a background callback is pending. Helpful for checking background state when
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* interrupts are disabled. */
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bool background_callback_pending(void);
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/* During soft reset, remove all pending callbacks and clear the critical section flag */
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void background_callback_reset(void);
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/* Sometimes background callbacks must be blocked. Use these functions to
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* bracket the section of code where this is the case. These calls nest, and
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* begins must be balanced with ends.
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*/
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void background_callback_prevent(void);
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void background_callback_allow(void);
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/*
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* Background callbacks may stop objects from being collected
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*/
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void background_callback_gc_collect(void);
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