add circuitpython code

1 files changed, 93 insertions, 0 deletions

diff --git a/circuitpython/supervisor/background_callback.h b/circuitpython/supervisor/background_callback.h
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+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2020 Jeff Epler for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef CIRCUITPY_INCLUDED_SUPERVISOR_BACKGROUND_CALLBACK_H
+#define CIRCUITPY_INCLUDED_SUPERVISOR_BACKGROUND_CALLBACK_H
+
+#include <stdbool.h>
+
+/** Background callbacks are a linked list of tasks to call in the background.
+ *
+ * Include a member of type `background_callback_t` inside an object
+ * which needs to queue up background work, and zero-initialize it.
+ *
+ * To schedule the work, use background_callback_add, with fun as the
+ * function to call and data pointing to the object itself.
+ *
+ * Next time run_background_tasks_if_tick is called, the callback will
+ * be run and removed from the linked list.
+ *
+ * Queueing a task that is already queued does nothing.  Unconditionally
+ * re-queueing it from its own background task will cause it to run during the
+ * very next background-tasks invocation, leading to a CircuitPython freeze, so
+ * don't do that.
+ *
+ * background_callback_add can be called from interrupt context.
+ */
+typedef void (*background_callback_fun)(void *data);
+typedef struct background_callback {
+    background_callback_fun fun;
+    void *data;
+    struct background_callback *next;
+    struct background_callback *prev;
+} background_callback_t;
+
+/* Add a background callback for which 'fun' and 'data' were previously set */
+void background_callback_add_core(background_callback_t *cb);
+
+/* Add a background callback to the given function with the given data.  When
+ * the callback involves an object on the GC heap, the 'data' must be a pointer
+ * to that object itself, not an internal pointer.  Otherwise, it can be the
+ * case that no other references to the object itself survive, and the object
+ * becomes garbage collected while an outstanding background callback still
+ * exists.
+ */
+void background_callback_add(background_callback_t *cb, background_callback_fun fun, void *data);
+
+/* Run all background callbacks.  Normally, this is done by the supervisor
+ * whenever the list is non-empty */
+void background_callback_run_all(void);
+
+/* True when a background callback is pending. Helpful for checking background state when
+ * interrupts are disabled. */
+bool background_callback_pending(void);
+
+/* During soft reset, remove all pending callbacks and clear the critical section flag */
+void background_callback_reset(void);
+
+/* Sometimes background callbacks must be blocked.  Use these functions to
+ * bracket the section of code where this is the case.  These calls nest, and
+ * begins must be balanced with ends.
+ */
+void background_callback_begin_critical_section(void);
+void background_callback_end_critical_section(void);
+
+/*
+ * Background callbacks may stop objects from being collected
+ */
+void background_callback_gc_collect(void);
+
+#endif