Boot Linux faster!

Check our new training course

Boot Linux faster!

Check our new training course
and Creative Commons CC-BY-SA
lecture and lab materials

Bootlin logo

Elixir Cross Referencer

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
/*
 * Copyright (c) 2019 Peter Bigot Consulting, LLC
 * Copyright (c) 2020 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <kernel.h>
#include <sys/onoff.h>
#include <stdio.h>

#define SERVICE_REFS_MAX UINT16_MAX

/* Confirm consistency of public flags with private flags */
BUILD_ASSERT((ONOFF_FLAG_ERROR | ONOFF_FLAG_ONOFF | ONOFF_FLAG_TRANSITION)
	     < BIT(3));

#define ONOFF_FLAG_PROCESSING BIT(3)
#define ONOFF_FLAG_COMPLETE BIT(4)
#define ONOFF_FLAG_RECHECK BIT(5)

/* These symbols in the ONOFF_FLAGS namespace identify bits in
 * onoff_manager::flags that indicate the state of the machine.  The
 * bits are manipulated by process_event() under lock, and actions
 * cued by bit values are executed outside of lock within
 * process_event().
 *
 * * ERROR indicates that the machine is in an error state.  When
 *   this bit is set ONOFF will be cleared.
 * * ONOFF indicates whether the target/current state is off (clear)
 *   or on (set).
 * * TRANSITION indicates whether a service transition function is in
 *   progress.  It combines with ONOFF to identify start and stop
 *   transitions, and with ERROR to identify a reset transition.
 * * PROCESSING indicates that the process_event() loop is active.  It
 *   is used to defer initiation of transitions and other complex
 *   state changes while invoking notifications associated with a
 *   state transition.  This bounds the  depth by limiting
 *   active process_event() call stacks to two instances.  State changes
 *   initiated by a nested call will be executed when control returns
 *   to the parent call.
 * * COMPLETE indicates that a transition completion notification has
 *   been received.  This flag is set in the notification, and cleared
 *   by process_events() which is invoked from the notification.  In
 *   the case of nested process_events() the processing is deferred to
 *   the top invocation.
 * * RECHECK indicates that a state transition has completed but
 *   process_events() must re-check the overall state to confirm no
 *   additional transitions are required.  This is used to simplfy the
 *   logic when, for example, a request is received during a
 *   transition to off, which means that when the transition completes
 *   a transition to on must be initiated if the request is still
 *   present.  Transition to ON with no remaining requests similarly
 *   triggers a recheck.
 */

/* Identify the events that can trigger state changes, as well as an
 * internal state used when processing deferred actions.
 */
enum event_type {
	/* No-op event: used to process deferred changes.
	 *
	 * This event is local to the process loop.
	 */
	EVT_NOP,

	/* Completion of a service transition.
	 *
	 * This event is triggered by the transition notify callback.
	 * It can be received only when the machine is in a transition
	 * state (TO-ON, TO-OFF, or RESETTING).
	 */
	EVT_COMPLETE,

	/* Reassess whether a transition from a stable state is needed.
	 *
	 * This event causes:
	 * * a start from OFF when there are clients;
	 * * a stop from ON when there are no clients;
	 * * a reset from ERROR when there are clients.
	 *
	 * The client list can change while the manager lock is
	 * released (e.g. during client and monitor notifications and
	 * transition initiations), so this event records the
	 * potential for these state changes, and process_event() ...
	 *
	 */
	EVT_RECHECK,

	/* Transition to on.
	 *
	 * This is synthesized from EVT_RECHECK in a non-nested
	 * process_event() when state OFF is confirmed with a
	 * non-empty client (request) list.
	 */
	EVT_START,

	/* Transition to off.
	 *
	 * This is synthesized from EVT_RECHECK in a non-nested
	 * process_event() when state ON is confirmed with a
	 * zero reference count.
	 */
	EVT_STOP,

	/* Transition to resetting.
	 *
	 * This is synthesized from EVT_RECHECK in a non-nested
	 * process_event() when state ERROR is confirmed with a
	 * non-empty client (reset) list.
	 */
	EVT_RESET,
};

static void set_state(struct onoff_manager *mgr,
		      uint32_t state)
{
	mgr->flags = (state & ONOFF_STATE_MASK)
		     | (mgr->flags & ~ONOFF_STATE_MASK);
}

static int validate_args(const struct onoff_manager *mgr,
			 struct onoff_client *cli)
{
	if ((mgr == NULL) || (cli == NULL)) {
		return -EINVAL;
	}

	int rv = sys_notify_validate(&cli->notify);

	if ((rv == 0)
	    && ((cli->notify.flags
		 & ~BIT_MASK(ONOFF_CLIENT_EXTENSION_POS)) != 0)) {
		rv = -EINVAL;
	}

	return rv;
}

int onoff_manager_init(struct onoff_manager *mgr,
		       const struct onoff_transitions *transitions)
{
	if ((mgr == NULL)
	    || (transitions == NULL)
	    || (transitions->start == NULL)
	    || (transitions->stop == NULL)) {
		return -EINVAL;
	}

	*mgr = (struct onoff_manager)ONOFF_MANAGER_INITIALIZER(transitions);

	return 0;
}

static void notify_monitors(struct onoff_manager *mgr,
			    uint32_t state,
			    int res)
{
	sys_slist_t *mlist = &mgr->monitors;
	struct onoff_monitor *mon;
	struct onoff_monitor *tmp;

	SYS_SLIST_FOR_EACH_CONTAINER_SAFE(mlist, mon, tmp, node) {
		mon->callback(mgr, mon, state, res);
	}
}

static void notify_one(struct onoff_manager *mgr,
		       struct onoff_client *cli,
		       uint32_t state,
		       int res)
{
	onoff_client_callback cb =
		(onoff_client_callback)sys_notify_finalize(&cli->notify, res);

	if (cb) {
		cb(mgr, cli, state, res);
	}
}

static void notify_all(struct onoff_manager *mgr,
		       sys_slist_t *list,
		       uint32_t state,
		       int res)
{
	while (!sys_slist_is_empty(list)) {
		sys_snode_t *node = sys_slist_get_not_empty(list);
		struct onoff_client *cli =
			CONTAINER_OF(node,
				     struct onoff_client,
				     node);

		notify_one(mgr, cli, state, res);
	}
}

static void process_event(struct onoff_manager *mgr,
			  int evt,
			  k_spinlock_key_t key);

static void transition_complete(struct onoff_manager *mgr,
				int res)
{
	k_spinlock_key_t key = k_spin_lock(&mgr->lock);

	mgr->last_res = res;
	process_event(mgr, EVT_COMPLETE, key);
}

/* Detect whether static state requires a transition. */
static int process_recheck(struct onoff_manager *mgr)
{
	int evt = EVT_NOP;
	uint32_t state = mgr->flags & ONOFF_STATE_MASK;

	if ((state == ONOFF_STATE_OFF)
	    && !sys_slist_is_empty(&mgr->clients)) {
		evt = EVT_START;
	} else if ((state == ONOFF_STATE_ON)
		   && (mgr->refs == 0U)) {
		evt = EVT_STOP;
	} else if ((state == ONOFF_STATE_ERROR)
		   && !sys_slist_is_empty(&mgr->clients)) {
		evt = EVT_RESET;
	}

	return evt;
}

/* Process a transition completion.
 *
 * If the completion requires notifying clients, the clients are moved
 * from the manager to the output list for notification.
 */
static void process_complete(struct onoff_manager *mgr,
			     sys_slist_t *clients,
			     int res)
{
	uint32_t state = mgr->flags & ONOFF_STATE_MASK;

	if (res < 0) {
		/* Enter ERROR state and notify all clients. */
		*clients = mgr->clients;
		sys_slist_init(&mgr->clients);
		set_state(mgr, ONOFF_STATE_ERROR);
	} else if ((state == ONOFF_STATE_TO_ON)
		   || (state == ONOFF_STATE_RESETTING)) {
		*clients = mgr->clients;
		sys_slist_init(&mgr->clients);

		if (state == ONOFF_STATE_TO_ON) {
			struct onoff_client *cp;

			/* Increment reference count for all remaining
			 * clients and enter ON state.
			 */
			SYS_SLIST_FOR_EACH_CONTAINER(clients, cp, node) {
				mgr->refs += 1U;
			}

			set_state(mgr, ONOFF_STATE_ON);
		} else {
			__ASSERT_NO_MSG(state == ONOFF_STATE_RESETTING);

			set_state(mgr, ONOFF_STATE_OFF);
		}
		if (process_recheck(mgr) != EVT_NOP) {
			mgr->flags |= ONOFF_FLAG_RECHECK;
		}
	} else if (state == ONOFF_STATE_TO_OFF) {
		/* Any active clients are requests waiting for this
		 * transition to complete.  Queue a RECHECK event to
		 * ensure we don't miss them if we don't unlock to
		 * tell anybody about the completion.
		 */
		set_state(mgr, ONOFF_STATE_OFF);
		if (process_recheck(mgr) != EVT_NOP) {
			mgr->flags |= ONOFF_FLAG_RECHECK;
		}
	} else {
		__ASSERT_NO_MSG(false);
	}
}

/* There are two points in the state machine where the machine is
 * unlocked to perform some external action:
 * * Initiation of an transition due to some event;
 * * Invocation of the user-specified callback when a stable state is
 *   reached or an error detected.
 *
 * Events received during these unlocked periods are recorded in the
 * state, but processing is deferred to the top-level invocation which
 * will loop to handle any events that occurred during the unlocked
 * regions.
 */
static void process_event(struct onoff_manager *mgr,
			  int evt,
			  k_spinlock_key_t key)
{
	sys_slist_t clients;
	uint32_t state = mgr->flags & ONOFF_STATE_MASK;
	int res = 0;
	bool processing = ((mgr->flags & ONOFF_FLAG_PROCESSING) != 0);

	__ASSERT_NO_MSG(evt != EVT_NOP);

	/* If this is a nested call record the event for processing in
	 * the top invocation.
	 */
	if (processing) {
		if (evt == EVT_COMPLETE) {
			mgr->flags |= ONOFF_FLAG_COMPLETE;
		} else {
			__ASSERT_NO_MSG(evt == EVT_RECHECK);

			mgr->flags |= ONOFF_FLAG_RECHECK;
		}

		goto out;
	}

	sys_slist_init(&clients);
	do {
		onoff_transition_fn transit = NULL;

		if (evt == EVT_RECHECK) {
			evt = process_recheck(mgr);
		}

		if (evt == EVT_NOP) {
			break;
		}

		res = 0;
		if (evt == EVT_COMPLETE) {
			res = mgr->last_res;
			process_complete(mgr, &clients, res);
			/* NB: This can trigger a RECHECK */
		} else if (evt == EVT_START) {
			__ASSERT_NO_MSG(state == ONOFF_STATE_OFF);
			__ASSERT_NO_MSG(!sys_slist_is_empty(&mgr->clients));

			transit = mgr->transitions->start;
			__ASSERT_NO_MSG(transit != NULL);
			set_state(mgr, ONOFF_STATE_TO_ON);
		} else if (evt == EVT_STOP) {
			__ASSERT_NO_MSG(state == ONOFF_STATE_ON);
			__ASSERT_NO_MSG(mgr->refs == 0);

			transit = mgr->transitions->stop;
			__ASSERT_NO_MSG(transit != NULL);
			set_state(mgr, ONOFF_STATE_TO_OFF);
		} else if (evt == EVT_RESET) {
			__ASSERT_NO_MSG(state == ONOFF_STATE_ERROR);
			__ASSERT_NO_MSG(!sys_slist_is_empty(&mgr->clients));

			transit = mgr->transitions->reset;
			__ASSERT_NO_MSG(transit != NULL);
			set_state(mgr, ONOFF_STATE_RESETTING);
		} else {
			__ASSERT_NO_MSG(false);
		}

		/* Have to unlock and do something if any of:
		 * * We changed state and there are monitors;
		 * * We completed a transition and there are clients to notify;
		 * * We need to initiate a transition.
		 */
		bool do_monitors = (state != (mgr->flags & ONOFF_STATE_MASK))
				   && !sys_slist_is_empty(&mgr->monitors);

		evt = EVT_NOP;
		if (do_monitors
		    || !sys_slist_is_empty(&clients)
		    || (transit != NULL)) {
			uint32_t flags = mgr->flags | ONOFF_FLAG_PROCESSING;

			mgr->flags = flags;
			state = flags & ONOFF_STATE_MASK;

			k_spin_unlock(&mgr->lock, key);

			if (do_monitors) {
				notify_monitors(mgr, state, res);
			}

			if (!sys_slist_is_empty(&clients)) {
				notify_all(mgr, &clients, state, res);
			}

			if (transit != NULL) {
				transit(mgr, transition_complete);
			}

			key = k_spin_lock(&mgr->lock);
			mgr->flags &= ~ONOFF_FLAG_PROCESSING;
			state = mgr->flags & ONOFF_STATE_MASK;
		}

		/* Process deferred events.  Completion takes priority
		 * over recheck.
		 */
		if ((mgr->flags & ONOFF_FLAG_COMPLETE) != 0) {
			mgr->flags &= ~ONOFF_FLAG_COMPLETE;
			evt = EVT_COMPLETE;
		} else if ((mgr->flags & ONOFF_FLAG_RECHECK) != 0) {
			mgr->flags &= ~ONOFF_FLAG_RECHECK;
			evt = EVT_RECHECK;
		}

		state = mgr->flags & ONOFF_STATE_MASK;
	} while (evt != EVT_NOP);

out:
	k_spin_unlock(&mgr->lock, key);
}

int onoff_request(struct onoff_manager *mgr,
		  struct onoff_client *cli)
{
	bool add_client = false;        /* add client to pending list */
	bool start = false;             /* trigger a start transition */
	bool notify = false;            /* do client notification */
	int rv = validate_args(mgr, cli);

	if (rv < 0) {
		return rv;
	}

	k_spinlock_key_t key = k_spin_lock(&mgr->lock);
	uint32_t state = mgr->flags & ONOFF_STATE_MASK;

	/* Reject if this would overflow the reference count. */
	if (mgr->refs == SERVICE_REFS_MAX) {
		rv = -EAGAIN;
		goto out;
	}

	rv = state;
	if (state == ONOFF_STATE_ON) {
		/* Increment reference count, notify in exit */
		notify = true;
		mgr->refs += 1U;
	} else if ((state == ONOFF_STATE_OFF)
		   || (state == ONOFF_STATE_TO_OFF)
		   || (state == ONOFF_STATE_TO_ON)) {
		/* Start if OFF, queue client */
		start = (state == ONOFF_STATE_OFF);
		add_client = true;
	} else if (state == ONOFF_STATE_RESETTING) {
		rv = -ENOTSUP;
	} else {
		__ASSERT_NO_MSG(state == ONOFF_STATE_ERROR);
		rv = -EIO;
	}

out:
	if (add_client) {
		sys_slist_append(&mgr->clients, &cli->node);
	}

	if (start) {
		process_event(mgr, EVT_RECHECK, key);
	} else {
		k_spin_unlock(&mgr->lock, key);

		if (notify) {
			notify_one(mgr, cli, state, 0);
		}
	}

	return rv;
}

int onoff_release(struct onoff_manager *mgr)
{
	bool stop = false;      /* trigger a stop transition */

	k_spinlock_key_t key = k_spin_lock(&mgr->lock);
	uint32_t state = mgr->flags & ONOFF_STATE_MASK;
	int rv = state;

	if (state != ONOFF_STATE_ON) {
		if (state == ONOFF_STATE_ERROR) {
			rv = -EIO;
		} else {
			rv = -ENOTSUP;
		}
		goto out;
	}

	__ASSERT_NO_MSG(mgr->refs > 0);
	mgr->refs -= 1U;
	stop = (mgr->refs == 0);

out:
	if (stop) {
		process_event(mgr, EVT_RECHECK, key);
	} else {
		k_spin_unlock(&mgr->lock, key);
	}

	return rv;
}

int onoff_reset(struct onoff_manager *mgr,
		struct onoff_client *cli)
{
	bool reset = false;
	int rv = validate_args(mgr, cli);

	if ((rv >= 0)
	    && (mgr->transitions->reset == NULL)) {
		rv = -ENOTSUP;
	}

	if (rv < 0) {
		return rv;
	}

	k_spinlock_key_t key = k_spin_lock(&mgr->lock);
	uint32_t state = mgr->flags & ONOFF_STATE_MASK;

	rv = state;

	if ((state & ONOFF_FLAG_ERROR) == 0) {
		rv = -EALREADY;
	} else {
		reset = (state != ONOFF_STATE_RESETTING);
		sys_slist_append(&mgr->clients, &cli->node);
	}

	if (reset) {
		process_event(mgr, EVT_RECHECK, key);
	} else {
		k_spin_unlock(&mgr->lock, key);
	}

	return rv;
}

int onoff_cancel(struct onoff_manager *mgr,
		 struct onoff_client *cli)
{
	if ((mgr == NULL) || (cli == NULL)) {
		return -EINVAL;
	}

	int rv = -EALREADY;
	k_spinlock_key_t key = k_spin_lock(&mgr->lock);
	uint32_t state = mgr->flags & ONOFF_STATE_MASK;

	if (sys_slist_find_and_remove(&mgr->clients, &cli->node)) {
		__ASSERT_NO_MSG((state == ONOFF_STATE_TO_ON)
				|| (state == ONOFF_STATE_TO_OFF)
				|| (state == ONOFF_STATE_RESETTING));
		rv = state;
	}

	k_spin_unlock(&mgr->lock, key);

	return rv;
}

int onoff_monitor_register(struct onoff_manager *mgr,
			   struct onoff_monitor *mon)
{
	if ((mgr == NULL)
	    || (mon == NULL)
	    || (mon->callback == NULL)) {
		return -EINVAL;
	}

	k_spinlock_key_t key = k_spin_lock(&mgr->lock);

	sys_slist_append(&mgr->monitors, &mon->node);

	k_spin_unlock(&mgr->lock, key);

	return 0;
}

int onoff_monitor_unregister(struct onoff_manager *mgr,
			     struct onoff_monitor *mon)
{
	int rv = -EINVAL;

	if ((mgr == NULL)
	    || (mon == NULL)) {
		return rv;
	}

	k_spinlock_key_t key = k_spin_lock(&mgr->lock);

	if (sys_slist_find_and_remove(&mgr->monitors, &mon->node)) {
		rv = 0;
	}

	k_spin_unlock(&mgr->lock, key);

	return rv;
}

int onoff_sync_lock(struct onoff_sync_service *srv,
		    k_spinlock_key_t *keyp)
{
	*keyp = k_spin_lock(&srv->lock);
	return srv->count;
}

int onoff_sync_finalize(struct onoff_sync_service *srv,
			k_spinlock_key_t key,
			struct onoff_client *cli,
			int res,
			bool on)
{
	uint32_t state = ONOFF_STATE_ON;

	/* Clear errors visible when locked.  If they are to be
	 * preserved the caller must finalize with the previous
	 * error code.
	 */
	if (srv->count < 0) {
		srv->count = 0;
	}
	if (res < 0) {
		srv->count = res;
		state = ONOFF_STATE_ERROR;
	} else if (on) {
		srv->count += 1;
	} else {
		srv->count -= 1;
		/* state would be either off or on, but since
		 * callbacks are used only when turning on don't
		 * bother changing it.
		 */
	}

	int rv = srv->count;

	k_spin_unlock(&srv->lock, key);

	if (cli) {
		/* Detect service mis-use: onoff does not callback on transition
		 * to off, so no client should have been passed.
		 */
		__ASSERT_NO_MSG(on);
		notify_one(NULL, cli, state, res);
	}

	return rv;
}