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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Multiplexer subsystem
4 *
5 * Copyright (C) 2017 Axentia Technologies AB
6 *
7 * Author: Peter Rosin <peda@axentia.se>
8 */
9
10#define pr_fmt(fmt) "mux-core: " fmt
11
12#include <linux/delay.h>
13#include <linux/device.h>
14#include <linux/err.h>
15#include <linux/export.h>
16#include <linux/idr.h>
17#include <linux/init.h>
18#include <linux/module.h>
19#include <linux/mux/consumer.h>
20#include <linux/mux/driver.h>
21#include <linux/of.h>
22#include <linux/of_platform.h>
23#include <linux/slab.h>
24
25/*
26 * The idle-as-is "state" is not an actual state that may be selected, it
27 * only implies that the state should not be changed. So, use that state
28 * as indication that the cached state of the multiplexer is unknown.
29 */
30#define MUX_CACHE_UNKNOWN MUX_IDLE_AS_IS
31
32/**
33 * struct mux_state - Represents a mux controller state specific to a given
34 * consumer.
35 * @mux: Pointer to a mux controller.
36 * @state: State of the mux to be selected.
37 *
38 * This structure is specific to the consumer that acquires it and has
39 * information specific to that consumer.
40 */
41struct mux_state {
42 struct mux_control *mux;
43 unsigned int state;
44};
45
46static struct class mux_class = {
47 .name = "mux",
48 .owner = THIS_MODULE,
49};
50
51static DEFINE_IDA(mux_ida);
52
53static int __init mux_init(void)
54{
55 ida_init(&mux_ida);
56 return class_register(&mux_class);
57}
58
59static void __exit mux_exit(void)
60{
61 class_unregister(&mux_class);
62 ida_destroy(&mux_ida);
63}
64
65static void mux_chip_release(struct device *dev)
66{
67 struct mux_chip *mux_chip = to_mux_chip(dev);
68
69 ida_simple_remove(&mux_ida, mux_chip->id);
70 kfree(mux_chip);
71}
72
73static const struct device_type mux_type = {
74 .name = "mux-chip",
75 .release = mux_chip_release,
76};
77
78/**
79 * mux_chip_alloc() - Allocate a mux-chip.
80 * @dev: The parent device implementing the mux interface.
81 * @controllers: The number of mux controllers to allocate for this chip.
82 * @sizeof_priv: Size of extra memory area for private use by the caller.
83 *
84 * After allocating the mux-chip with the desired number of mux controllers
85 * but before registering the chip, the mux driver is required to configure
86 * the number of valid mux states in the mux_chip->mux[N].states members and
87 * the desired idle state in the returned mux_chip->mux[N].idle_state members.
88 * The default idle state is MUX_IDLE_AS_IS. The mux driver also needs to
89 * provide a pointer to the operations struct in the mux_chip->ops member
90 * before registering the mux-chip with mux_chip_register.
91 *
92 * Return: A pointer to the new mux-chip, or an ERR_PTR with a negative errno.
93 */
94struct mux_chip *mux_chip_alloc(struct device *dev,
95 unsigned int controllers, size_t sizeof_priv)
96{
97 struct mux_chip *mux_chip;
98 int i;
99
100 if (WARN_ON(!dev || !controllers))
101 return ERR_PTR(-EINVAL);
102
103 mux_chip = kzalloc(sizeof(*mux_chip) +
104 controllers * sizeof(*mux_chip->mux) +
105 sizeof_priv, GFP_KERNEL);
106 if (!mux_chip)
107 return ERR_PTR(-ENOMEM);
108
109 mux_chip->mux = (struct mux_control *)(mux_chip + 1);
110 mux_chip->dev.class = &mux_class;
111 mux_chip->dev.type = &mux_type;
112 mux_chip->dev.parent = dev;
113 mux_chip->dev.of_node = dev->of_node;
114 dev_set_drvdata(&mux_chip->dev, mux_chip);
115
116 mux_chip->id = ida_simple_get(&mux_ida, 0, 0, GFP_KERNEL);
117 if (mux_chip->id < 0) {
118 int err = mux_chip->id;
119
120 pr_err("muxchipX failed to get a device id\n");
121 kfree(mux_chip);
122 return ERR_PTR(err);
123 }
124 dev_set_name(&mux_chip->dev, "muxchip%d", mux_chip->id);
125
126 mux_chip->controllers = controllers;
127 for (i = 0; i < controllers; ++i) {
128 struct mux_control *mux = &mux_chip->mux[i];
129
130 mux->chip = mux_chip;
131 sema_init(&mux->lock, 1);
132 mux->cached_state = MUX_CACHE_UNKNOWN;
133 mux->idle_state = MUX_IDLE_AS_IS;
134 mux->last_change = ktime_get();
135 }
136
137 device_initialize(&mux_chip->dev);
138
139 return mux_chip;
140}
141EXPORT_SYMBOL_GPL(mux_chip_alloc);
142
143static int mux_control_set(struct mux_control *mux, int state)
144{
145 int ret = mux->chip->ops->set(mux, state);
146
147 mux->cached_state = ret < 0 ? MUX_CACHE_UNKNOWN : state;
148 if (ret >= 0)
149 mux->last_change = ktime_get();
150
151 return ret;
152}
153
154/**
155 * mux_chip_register() - Register a mux-chip, thus readying the controllers
156 * for use.
157 * @mux_chip: The mux-chip to register.
158 *
159 * Do not retry registration of the same mux-chip on failure. You should
160 * instead put it away with mux_chip_free() and allocate a new one, if you
161 * for some reason would like to retry registration.
162 *
163 * Return: Zero on success or a negative errno on error.
164 */
165int mux_chip_register(struct mux_chip *mux_chip)
166{
167 int i;
168 int ret;
169
170 for (i = 0; i < mux_chip->controllers; ++i) {
171 struct mux_control *mux = &mux_chip->mux[i];
172
173 if (mux->idle_state == mux->cached_state)
174 continue;
175
176 ret = mux_control_set(mux, mux->idle_state);
177 if (ret < 0) {
178 dev_err(&mux_chip->dev, "unable to set idle state\n");
179 return ret;
180 }
181 }
182
183 ret = device_add(&mux_chip->dev);
184 if (ret < 0)
185 dev_err(&mux_chip->dev,
186 "device_add failed in %s: %d\n", __func__, ret);
187 return ret;
188}
189EXPORT_SYMBOL_GPL(mux_chip_register);
190
191/**
192 * mux_chip_unregister() - Take the mux-chip off-line.
193 * @mux_chip: The mux-chip to unregister.
194 *
195 * mux_chip_unregister() reverses the effects of mux_chip_register().
196 * But not completely, you should not try to call mux_chip_register()
197 * on a mux-chip that has been registered before.
198 */
199void mux_chip_unregister(struct mux_chip *mux_chip)
200{
201 device_del(&mux_chip->dev);
202}
203EXPORT_SYMBOL_GPL(mux_chip_unregister);
204
205/**
206 * mux_chip_free() - Free the mux-chip for good.
207 * @mux_chip: The mux-chip to free.
208 *
209 * mux_chip_free() reverses the effects of mux_chip_alloc().
210 */
211void mux_chip_free(struct mux_chip *mux_chip)
212{
213 if (!mux_chip)
214 return;
215
216 put_device(&mux_chip->dev);
217}
218EXPORT_SYMBOL_GPL(mux_chip_free);
219
220static void devm_mux_chip_release(struct device *dev, void *res)
221{
222 struct mux_chip *mux_chip = *(struct mux_chip **)res;
223
224 mux_chip_free(mux_chip);
225}
226
227/**
228 * devm_mux_chip_alloc() - Resource-managed version of mux_chip_alloc().
229 * @dev: The parent device implementing the mux interface.
230 * @controllers: The number of mux controllers to allocate for this chip.
231 * @sizeof_priv: Size of extra memory area for private use by the caller.
232 *
233 * See mux_chip_alloc() for more details.
234 *
235 * Return: A pointer to the new mux-chip, or an ERR_PTR with a negative errno.
236 */
237struct mux_chip *devm_mux_chip_alloc(struct device *dev,
238 unsigned int controllers,
239 size_t sizeof_priv)
240{
241 struct mux_chip **ptr, *mux_chip;
242
243 ptr = devres_alloc(devm_mux_chip_release, sizeof(*ptr), GFP_KERNEL);
244 if (!ptr)
245 return ERR_PTR(-ENOMEM);
246
247 mux_chip = mux_chip_alloc(dev, controllers, sizeof_priv);
248 if (IS_ERR(mux_chip)) {
249 devres_free(ptr);
250 return mux_chip;
251 }
252
253 *ptr = mux_chip;
254 devres_add(dev, ptr);
255
256 return mux_chip;
257}
258EXPORT_SYMBOL_GPL(devm_mux_chip_alloc);
259
260static void devm_mux_chip_reg_release(struct device *dev, void *res)
261{
262 struct mux_chip *mux_chip = *(struct mux_chip **)res;
263
264 mux_chip_unregister(mux_chip);
265}
266
267/**
268 * devm_mux_chip_register() - Resource-managed version mux_chip_register().
269 * @dev: The parent device implementing the mux interface.
270 * @mux_chip: The mux-chip to register.
271 *
272 * See mux_chip_register() for more details.
273 *
274 * Return: Zero on success or a negative errno on error.
275 */
276int devm_mux_chip_register(struct device *dev,
277 struct mux_chip *mux_chip)
278{
279 struct mux_chip **ptr;
280 int res;
281
282 ptr = devres_alloc(devm_mux_chip_reg_release, sizeof(*ptr), GFP_KERNEL);
283 if (!ptr)
284 return -ENOMEM;
285
286 res = mux_chip_register(mux_chip);
287 if (res) {
288 devres_free(ptr);
289 return res;
290 }
291
292 *ptr = mux_chip;
293 devres_add(dev, ptr);
294
295 return res;
296}
297EXPORT_SYMBOL_GPL(devm_mux_chip_register);
298
299/**
300 * mux_control_states() - Query the number of multiplexer states.
301 * @mux: The mux-control to query.
302 *
303 * Return: The number of multiplexer states.
304 */
305unsigned int mux_control_states(struct mux_control *mux)
306{
307 return mux->states;
308}
309EXPORT_SYMBOL_GPL(mux_control_states);
310
311/*
312 * The mux->lock must be down when calling this function.
313 */
314static int __mux_control_select(struct mux_control *mux, int state)
315{
316 int ret;
317
318 if (WARN_ON(state < 0 || state >= mux->states))
319 return -EINVAL;
320
321 if (mux->cached_state == state)
322 return 0;
323
324 ret = mux_control_set(mux, state);
325 if (ret >= 0)
326 return 0;
327
328 /* The mux update failed, try to revert if appropriate... */
329 if (mux->idle_state != MUX_IDLE_AS_IS)
330 mux_control_set(mux, mux->idle_state);
331
332 return ret;
333}
334
335static void mux_control_delay(struct mux_control *mux, unsigned int delay_us)
336{
337 ktime_t delayend;
338 s64 remaining;
339
340 if (!delay_us)
341 return;
342
343 delayend = ktime_add_us(mux->last_change, delay_us);
344 remaining = ktime_us_delta(delayend, ktime_get());
345 if (remaining > 0)
346 fsleep(remaining);
347}
348
349/**
350 * mux_control_select_delay() - Select the given multiplexer state.
351 * @mux: The mux-control to request a change of state from.
352 * @state: The new requested state.
353 * @delay_us: The time to delay (in microseconds) if the mux state is changed.
354 *
355 * On successfully selecting the mux-control state, it will be locked until
356 * there is a call to mux_control_deselect(). If the mux-control is already
357 * selected when mux_control_select() is called, the caller will be blocked
358 * until mux_control_deselect() or mux_state_deselect() is called (by someone
359 * else).
360 *
361 * Therefore, make sure to call mux_control_deselect() when the operation is
362 * complete and the mux-control is free for others to use, but do not call
363 * mux_control_deselect() if mux_control_select() fails.
364 *
365 * Return: 0 when the mux-control state has the requested state or a negative
366 * errno on error.
367 */
368int mux_control_select_delay(struct mux_control *mux, unsigned int state,
369 unsigned int delay_us)
370{
371 int ret;
372
373 ret = down_killable(&mux->lock);
374 if (ret < 0)
375 return ret;
376
377 ret = __mux_control_select(mux, state);
378 if (ret >= 0)
379 mux_control_delay(mux, delay_us);
380
381 if (ret < 0)
382 up(&mux->lock);
383
384 return ret;
385}
386EXPORT_SYMBOL_GPL(mux_control_select_delay);
387
388/**
389 * mux_state_select_delay() - Select the given multiplexer state.
390 * @mstate: The mux-state to select.
391 * @delay_us: The time to delay (in microseconds) if the mux state is changed.
392 *
393 * On successfully selecting the mux-state, its mux-control will be locked
394 * until there is a call to mux_state_deselect(). If the mux-control is already
395 * selected when mux_state_select() is called, the caller will be blocked
396 * until mux_state_deselect() or mux_control_deselect() is called (by someone
397 * else).
398 *
399 * Therefore, make sure to call mux_state_deselect() when the operation is
400 * complete and the mux-control is free for others to use, but do not call
401 * mux_state_deselect() if mux_state_select() fails.
402 *
403 * Return: 0 when the mux-state has been selected or a negative
404 * errno on error.
405 */
406int mux_state_select_delay(struct mux_state *mstate, unsigned int delay_us)
407{
408 return mux_control_select_delay(mstate->mux, mstate->state, delay_us);
409}
410EXPORT_SYMBOL_GPL(mux_state_select_delay);
411
412/**
413 * mux_control_try_select_delay() - Try to select the given multiplexer state.
414 * @mux: The mux-control to request a change of state from.
415 * @state: The new requested state.
416 * @delay_us: The time to delay (in microseconds) if the mux state is changed.
417 *
418 * On successfully selecting the mux-control state, it will be locked until
419 * mux_control_deselect() is called.
420 *
421 * Therefore, make sure to call mux_control_deselect() when the operation is
422 * complete and the mux-control is free for others to use, but do not call
423 * mux_control_deselect() if mux_control_try_select() fails.
424 *
425 * Return: 0 when the mux-control state has the requested state or a negative
426 * errno on error. Specifically -EBUSY if the mux-control is contended.
427 */
428int mux_control_try_select_delay(struct mux_control *mux, unsigned int state,
429 unsigned int delay_us)
430{
431 int ret;
432
433 if (down_trylock(&mux->lock))
434 return -EBUSY;
435
436 ret = __mux_control_select(mux, state);
437 if (ret >= 0)
438 mux_control_delay(mux, delay_us);
439
440 if (ret < 0)
441 up(&mux->lock);
442
443 return ret;
444}
445EXPORT_SYMBOL_GPL(mux_control_try_select_delay);
446
447/**
448 * mux_state_try_select_delay() - Try to select the given multiplexer state.
449 * @mstate: The mux-state to select.
450 * @delay_us: The time to delay (in microseconds) if the mux state is changed.
451 *
452 * On successfully selecting the mux-state, its mux-control will be locked
453 * until mux_state_deselect() is called.
454 *
455 * Therefore, make sure to call mux_state_deselect() when the operation is
456 * complete and the mux-control is free for others to use, but do not call
457 * mux_state_deselect() if mux_state_try_select() fails.
458 *
459 * Return: 0 when the mux-state has been selected or a negative errno on
460 * error. Specifically -EBUSY if the mux-control is contended.
461 */
462int mux_state_try_select_delay(struct mux_state *mstate, unsigned int delay_us)
463{
464 return mux_control_try_select_delay(mstate->mux, mstate->state, delay_us);
465}
466EXPORT_SYMBOL_GPL(mux_state_try_select_delay);
467
468/**
469 * mux_control_deselect() - Deselect the previously selected multiplexer state.
470 * @mux: The mux-control to deselect.
471 *
472 * It is required that a single call is made to mux_control_deselect() for
473 * each and every successful call made to either of mux_control_select() or
474 * mux_control_try_select().
475 *
476 * Return: 0 on success and a negative errno on error. An error can only
477 * occur if the mux has an idle state. Note that even if an error occurs, the
478 * mux-control is unlocked and is thus free for the next access.
479 */
480int mux_control_deselect(struct mux_control *mux)
481{
482 int ret = 0;
483
484 if (mux->idle_state != MUX_IDLE_AS_IS &&
485 mux->idle_state != mux->cached_state)
486 ret = mux_control_set(mux, mux->idle_state);
487
488 up(&mux->lock);
489
490 return ret;
491}
492EXPORT_SYMBOL_GPL(mux_control_deselect);
493
494/**
495 * mux_state_deselect() - Deselect the previously selected multiplexer state.
496 * @mstate: The mux-state to deselect.
497 *
498 * It is required that a single call is made to mux_state_deselect() for
499 * each and every successful call made to either of mux_state_select() or
500 * mux_state_try_select().
501 *
502 * Return: 0 on success and a negative errno on error. An error can only
503 * occur if the mux has an idle state. Note that even if an error occurs, the
504 * mux-control is unlocked and is thus free for the next access.
505 */
506int mux_state_deselect(struct mux_state *mstate)
507{
508 return mux_control_deselect(mstate->mux);
509}
510EXPORT_SYMBOL_GPL(mux_state_deselect);
511
512/* Note this function returns a reference to the mux_chip dev. */
513static struct mux_chip *of_find_mux_chip_by_node(struct device_node *np)
514{
515 struct device *dev;
516
517 dev = class_find_device_by_of_node(&mux_class, np);
518
519 return dev ? to_mux_chip(dev) : NULL;
520}
521
522/*
523 * mux_get() - Get the mux-control for a device.
524 * @dev: The device that needs a mux-control.
525 * @mux_name: The name identifying the mux-control.
526 * @state: Pointer to where the requested state is returned, or NULL when
527 * the required multiplexer states are handled by other means.
528 *
529 * Return: A pointer to the mux-control, or an ERR_PTR with a negative errno.
530 */
531static struct mux_control *mux_get(struct device *dev, const char *mux_name,
532 unsigned int *state)
533{
534 struct device_node *np = dev->of_node;
535 struct of_phandle_args args;
536 struct mux_chip *mux_chip;
537 unsigned int controller;
538 int index = 0;
539 int ret;
540
541 if (mux_name) {
542 if (state)
543 index = of_property_match_string(np, "mux-state-names",
544 mux_name);
545 else
546 index = of_property_match_string(np, "mux-control-names",
547 mux_name);
548 if (index < 0) {
549 dev_err(dev, "mux controller '%s' not found\n",
550 mux_name);
551 return ERR_PTR(index);
552 }
553 }
554
555 if (state)
556 ret = of_parse_phandle_with_args(np,
557 "mux-states", "#mux-state-cells",
558 index, &args);
559 else
560 ret = of_parse_phandle_with_args(np,
561 "mux-controls", "#mux-control-cells",
562 index, &args);
563 if (ret) {
564 dev_err(dev, "%pOF: failed to get mux-%s %s(%i)\n",
565 np, state ? "state" : "control", mux_name ?: "", index);
566 return ERR_PTR(ret);
567 }
568
569 mux_chip = of_find_mux_chip_by_node(args.np);
570 of_node_put(args.np);
571 if (!mux_chip)
572 return ERR_PTR(-EPROBE_DEFER);
573
574 controller = 0;
575 if (state) {
576 if (args.args_count > 2 || args.args_count == 0 ||
577 (args.args_count < 2 && mux_chip->controllers > 1)) {
578 dev_err(dev, "%pOF: wrong #mux-state-cells for %pOF\n",
579 np, args.np);
580 put_device(&mux_chip->dev);
581 return ERR_PTR(-EINVAL);
582 }
583
584 if (args.args_count == 2) {
585 controller = args.args[0];
586 *state = args.args[1];
587 } else {
588 *state = args.args[0];
589 }
590
591 } else {
592 if (args.args_count > 1 ||
593 (!args.args_count && mux_chip->controllers > 1)) {
594 dev_err(dev, "%pOF: wrong #mux-control-cells for %pOF\n",
595 np, args.np);
596 put_device(&mux_chip->dev);
597 return ERR_PTR(-EINVAL);
598 }
599
600 if (args.args_count)
601 controller = args.args[0];
602 }
603
604 if (controller >= mux_chip->controllers) {
605 dev_err(dev, "%pOF: bad mux controller %u specified in %pOF\n",
606 np, controller, args.np);
607 put_device(&mux_chip->dev);
608 return ERR_PTR(-EINVAL);
609 }
610
611 return &mux_chip->mux[controller];
612}
613
614/**
615 * mux_control_get() - Get the mux-control for a device.
616 * @dev: The device that needs a mux-control.
617 * @mux_name: The name identifying the mux-control.
618 *
619 * Return: A pointer to the mux-control, or an ERR_PTR with a negative errno.
620 */
621struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
622{
623 return mux_get(dev, mux_name, NULL);
624}
625EXPORT_SYMBOL_GPL(mux_control_get);
626
627/**
628 * mux_control_put() - Put away the mux-control for good.
629 * @mux: The mux-control to put away.
630 *
631 * mux_control_put() reverses the effects of mux_control_get().
632 */
633void mux_control_put(struct mux_control *mux)
634{
635 put_device(&mux->chip->dev);
636}
637EXPORT_SYMBOL_GPL(mux_control_put);
638
639static void devm_mux_control_release(struct device *dev, void *res)
640{
641 struct mux_control *mux = *(struct mux_control **)res;
642
643 mux_control_put(mux);
644}
645
646/**
647 * devm_mux_control_get() - Get the mux-control for a device, with resource
648 * management.
649 * @dev: The device that needs a mux-control.
650 * @mux_name: The name identifying the mux-control.
651 *
652 * Return: Pointer to the mux-control, or an ERR_PTR with a negative errno.
653 */
654struct mux_control *devm_mux_control_get(struct device *dev,
655 const char *mux_name)
656{
657 struct mux_control **ptr, *mux;
658
659 ptr = devres_alloc(devm_mux_control_release, sizeof(*ptr), GFP_KERNEL);
660 if (!ptr)
661 return ERR_PTR(-ENOMEM);
662
663 mux = mux_control_get(dev, mux_name);
664 if (IS_ERR(mux)) {
665 devres_free(ptr);
666 return mux;
667 }
668
669 *ptr = mux;
670 devres_add(dev, ptr);
671
672 return mux;
673}
674EXPORT_SYMBOL_GPL(devm_mux_control_get);
675
676/*
677 * mux_state_get() - Get the mux-state for a device.
678 * @dev: The device that needs a mux-state.
679 * @mux_name: The name identifying the mux-state.
680 *
681 * Return: A pointer to the mux-state, or an ERR_PTR with a negative errno.
682 */
683static struct mux_state *mux_state_get(struct device *dev, const char *mux_name)
684{
685 struct mux_state *mstate;
686
687 mstate = kzalloc(sizeof(*mstate), GFP_KERNEL);
688 if (!mstate)
689 return ERR_PTR(-ENOMEM);
690
691 mstate->mux = mux_get(dev, mux_name, &mstate->state);
692 if (IS_ERR(mstate->mux)) {
693 int err = PTR_ERR(mstate->mux);
694
695 kfree(mstate);
696 return ERR_PTR(err);
697 }
698
699 return mstate;
700}
701
702/*
703 * mux_state_put() - Put away the mux-state for good.
704 * @mstate: The mux-state to put away.
705 *
706 * mux_state_put() reverses the effects of mux_state_get().
707 */
708static void mux_state_put(struct mux_state *mstate)
709{
710 mux_control_put(mstate->mux);
711 kfree(mstate);
712}
713
714static void devm_mux_state_release(struct device *dev, void *res)
715{
716 struct mux_state *mstate = *(struct mux_state **)res;
717
718 mux_state_put(mstate);
719}
720
721/**
722 * devm_mux_state_get() - Get the mux-state for a device, with resource
723 * management.
724 * @dev: The device that needs a mux-control.
725 * @mux_name: The name identifying the mux-control.
726 *
727 * Return: Pointer to the mux-state, or an ERR_PTR with a negative errno.
728 */
729struct mux_state *devm_mux_state_get(struct device *dev,
730 const char *mux_name)
731{
732 struct mux_state **ptr, *mstate;
733
734 ptr = devres_alloc(devm_mux_state_release, sizeof(*ptr), GFP_KERNEL);
735 if (!ptr)
736 return ERR_PTR(-ENOMEM);
737
738 mstate = mux_state_get(dev, mux_name);
739 if (IS_ERR(mstate)) {
740 devres_free(ptr);
741 return mstate;
742 }
743
744 *ptr = mstate;
745 devres_add(dev, ptr);
746
747 return mstate;
748}
749EXPORT_SYMBOL_GPL(devm_mux_state_get);
750
751/*
752 * Using subsys_initcall instead of module_init here to try to ensure - for
753 * the non-modular case - that the subsystem is initialized when mux consumers
754 * and mux controllers start to use it.
755 * For the modular case, the ordering is ensured with module dependencies.
756 */
757subsys_initcall(mux_init);
758module_exit(mux_exit);
759
760MODULE_DESCRIPTION("Multiplexer subsystem");
761MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
762MODULE_LICENSE("GPL v2");