1// SPDX-License-Identifier: GPL-2.0
2
3#include <linux/bitops.h>
4#include <linux/device.h>
5#include <linux/idr.h>
6#include <linux/init.h>
7#include <linux/interrupt.h>
8#include <linux/kdev_t.h>
9#include <linux/kstrtox.h>
10#include <linux/list.h>
11#include <linux/mutex.h>
12#include <linux/printk.h>
13#include <linux/slab.h>
14#include <linux/spinlock.h>
15#include <linux/string.h>
16#include <linux/sysfs.h>
17#include <linux/types.h>
18
19#include <linux/gpio/consumer.h>
20#include <linux/gpio/driver.h>
21
22#include "gpiolib.h"
23#include "gpiolib-sysfs.h"
24
25struct kernfs_node;
26
27#define GPIO_IRQF_TRIGGER_NONE 0
28#define GPIO_IRQF_TRIGGER_FALLING BIT(0)
29#define GPIO_IRQF_TRIGGER_RISING BIT(1)
30#define GPIO_IRQF_TRIGGER_BOTH (GPIO_IRQF_TRIGGER_FALLING | \
31 GPIO_IRQF_TRIGGER_RISING)
32
33struct gpiod_data {
34 struct gpio_desc *desc;
35
36 struct mutex mutex;
37 struct kernfs_node *value_kn;
38 int irq;
39 unsigned char irq_flags;
40
41 bool direction_can_change;
42};
43
44/*
45 * Lock to serialise gpiod export and unexport, and prevent re-export of
46 * gpiod whose chip is being unregistered.
47 */
48static DEFINE_MUTEX(sysfs_lock);
49
50/*
51 * /sys/class/gpio/gpioN... only for GPIOs that are exported
52 * /direction
53 * * MAY BE OMITTED if kernel won't allow direction changes
54 * * is read/write as "in" or "out"
55 * * may also be written as "high" or "low", initializing
56 * output value as specified ("out" implies "low")
57 * /value
58 * * always readable, subject to hardware behavior
59 * * may be writable, as zero/nonzero
60 * /edge
61 * * configures behavior of poll(2) on /value
62 * * available only if pin can generate IRQs on input
63 * * is read/write as "none", "falling", "rising", or "both"
64 * /active_low
65 * * configures polarity of /value
66 * * is read/write as zero/nonzero
67 * * also affects existing and subsequent "falling" and "rising"
68 * /edge configuration
69 */
70
71static ssize_t direction_show(struct device *dev,
72 struct device_attribute *attr, char *buf)
73{
74 struct gpiod_data *data = dev_get_drvdata(dev);
75 struct gpio_desc *desc = data->desc;
76 int value;
77
78 mutex_lock(&data->mutex);
79
80 gpiod_get_direction(desc);
81 value = !!test_bit(FLAG_IS_OUT, &desc->flags);
82
83 mutex_unlock(lock: &data->mutex);
84
85 return sysfs_emit(buf, fmt: "%s\n", value ? "out" : "in");
86}
87
88static ssize_t direction_store(struct device *dev,
89 struct device_attribute *attr, const char *buf, size_t size)
90{
91 struct gpiod_data *data = dev_get_drvdata(dev);
92 struct gpio_desc *desc = data->desc;
93 ssize_t status;
94
95 mutex_lock(&data->mutex);
96
97 if (sysfs_streq(s1: buf, s2: "high"))
98 status = gpiod_direction_output_raw(desc, value: 1);
99 else if (sysfs_streq(s1: buf, s2: "out") || sysfs_streq(s1: buf, s2: "low"))
100 status = gpiod_direction_output_raw(desc, value: 0);
101 else if (sysfs_streq(s1: buf, s2: "in"))
102 status = gpiod_direction_input(desc);
103 else
104 status = -EINVAL;
105
106 mutex_unlock(lock: &data->mutex);
107
108 return status ? : size;
109}
110static DEVICE_ATTR_RW(direction);
111
112static ssize_t value_show(struct device *dev,
113 struct device_attribute *attr, char *buf)
114{
115 struct gpiod_data *data = dev_get_drvdata(dev);
116 struct gpio_desc *desc = data->desc;
117 ssize_t status;
118
119 mutex_lock(&data->mutex);
120
121 status = gpiod_get_value_cansleep(desc);
122
123 mutex_unlock(lock: &data->mutex);
124
125 if (status < 0)
126 return status;
127
128 return sysfs_emit(buf, fmt: "%zd\n", status);
129}
130
131static ssize_t value_store(struct device *dev,
132 struct device_attribute *attr, const char *buf, size_t size)
133{
134 struct gpiod_data *data = dev_get_drvdata(dev);
135 struct gpio_desc *desc = data->desc;
136 ssize_t status;
137 long value;
138
139 status = kstrtol(s: buf, base: 0, res: &value);
140
141 mutex_lock(&data->mutex);
142
143 if (!test_bit(FLAG_IS_OUT, &desc->flags)) {
144 status = -EPERM;
145 } else if (status == 0) {
146 gpiod_set_value_cansleep(desc, value);
147 status = size;
148 }
149
150 mutex_unlock(lock: &data->mutex);
151
152 return status;
153}
154static DEVICE_ATTR_PREALLOC(value, S_IWUSR | S_IRUGO, value_show, value_store);
155
156static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
157{
158 struct gpiod_data *data = priv;
159
160 sysfs_notify_dirent(kn: data->value_kn);
161
162 return IRQ_HANDLED;
163}
164
165/* Caller holds gpiod-data mutex. */
166static int gpio_sysfs_request_irq(struct device *dev, unsigned char flags)
167{
168 struct gpiod_data *data = dev_get_drvdata(dev);
169 struct gpio_desc *desc = data->desc;
170 unsigned long irq_flags;
171 int ret;
172
173 data->irq = gpiod_to_irq(desc);
174 if (data->irq < 0)
175 return -EIO;
176
177 data->value_kn = sysfs_get_dirent(parent: dev->kobj.sd, name: "value");
178 if (!data->value_kn)
179 return -ENODEV;
180
181 irq_flags = IRQF_SHARED;
182 if (flags & GPIO_IRQF_TRIGGER_FALLING)
183 irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
184 IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING;
185 if (flags & GPIO_IRQF_TRIGGER_RISING)
186 irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
187 IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
188
189 /*
190 * FIXME: This should be done in the irq_request_resources callback
191 * when the irq is requested, but a few drivers currently fail
192 * to do so.
193 *
194 * Remove this redundant call (along with the corresponding
195 * unlock) when those drivers have been fixed.
196 */
197 ret = gpiochip_lock_as_irq(gc: desc->gdev->chip, offset: gpio_chip_hwgpio(desc));
198 if (ret < 0)
199 goto err_put_kn;
200
201 ret = request_any_context_irq(irq: data->irq, handler: gpio_sysfs_irq, flags: irq_flags,
202 name: "gpiolib", dev_id: data);
203 if (ret < 0)
204 goto err_unlock;
205
206 data->irq_flags = flags;
207
208 return 0;
209
210err_unlock:
211 gpiochip_unlock_as_irq(gc: desc->gdev->chip, offset: gpio_chip_hwgpio(desc));
212err_put_kn:
213 sysfs_put(kn: data->value_kn);
214
215 return ret;
216}
217
218/*
219 * Caller holds gpiod-data mutex (unless called after class-device
220 * deregistration).
221 */
222static void gpio_sysfs_free_irq(struct device *dev)
223{
224 struct gpiod_data *data = dev_get_drvdata(dev);
225 struct gpio_desc *desc = data->desc;
226
227 data->irq_flags = 0;
228 free_irq(data->irq, data);
229 gpiochip_unlock_as_irq(gc: desc->gdev->chip, offset: gpio_chip_hwgpio(desc));
230 sysfs_put(kn: data->value_kn);
231}
232
233static const char * const trigger_names[] = {
234 [GPIO_IRQF_TRIGGER_NONE] = "none",
235 [GPIO_IRQF_TRIGGER_FALLING] = "falling",
236 [GPIO_IRQF_TRIGGER_RISING] = "rising",
237 [GPIO_IRQF_TRIGGER_BOTH] = "both",
238};
239
240static ssize_t edge_show(struct device *dev,
241 struct device_attribute *attr, char *buf)
242{
243 struct gpiod_data *data = dev_get_drvdata(dev);
244 int flags;
245
246 mutex_lock(&data->mutex);
247
248 flags = data->irq_flags;
249
250 mutex_unlock(lock: &data->mutex);
251
252 if (flags >= ARRAY_SIZE(trigger_names))
253 return 0;
254
255 return sysfs_emit(buf, fmt: "%s\n", trigger_names[flags]);
256}
257
258static ssize_t edge_store(struct device *dev,
259 struct device_attribute *attr, const char *buf, size_t size)
260{
261 struct gpiod_data *data = dev_get_drvdata(dev);
262 ssize_t status = size;
263 int flags;
264
265 flags = sysfs_match_string(trigger_names, buf);
266 if (flags < 0)
267 return flags;
268
269 mutex_lock(&data->mutex);
270
271 if (flags == data->irq_flags) {
272 status = size;
273 goto out_unlock;
274 }
275
276 if (data->irq_flags)
277 gpio_sysfs_free_irq(dev);
278
279 if (flags) {
280 status = gpio_sysfs_request_irq(dev, flags);
281 if (!status)
282 status = size;
283 }
284
285out_unlock:
286 mutex_unlock(lock: &data->mutex);
287
288 return status;
289}
290static DEVICE_ATTR_RW(edge);
291
292/* Caller holds gpiod-data mutex. */
293static int gpio_sysfs_set_active_low(struct device *dev, int value)
294{
295 struct gpiod_data *data = dev_get_drvdata(dev);
296 struct gpio_desc *desc = data->desc;
297 int status = 0;
298 unsigned int flags = data->irq_flags;
299
300 if (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) == !!value)
301 return 0;
302
303 assign_bit(FLAG_ACTIVE_LOW, addr: &desc->flags, value);
304
305 /* reconfigure poll(2) support if enabled on one edge only */
306 if (flags == GPIO_IRQF_TRIGGER_FALLING ||
307 flags == GPIO_IRQF_TRIGGER_RISING) {
308 gpio_sysfs_free_irq(dev);
309 status = gpio_sysfs_request_irq(dev, flags);
310 }
311
312 return status;
313}
314
315static ssize_t active_low_show(struct device *dev,
316 struct device_attribute *attr, char *buf)
317{
318 struct gpiod_data *data = dev_get_drvdata(dev);
319 struct gpio_desc *desc = data->desc;
320 int value;
321
322 mutex_lock(&data->mutex);
323
324 value = !!test_bit(FLAG_ACTIVE_LOW, &desc->flags);
325
326 mutex_unlock(lock: &data->mutex);
327
328 return sysfs_emit(buf, fmt: "%d\n", value);
329}
330
331static ssize_t active_low_store(struct device *dev,
332 struct device_attribute *attr, const char *buf, size_t size)
333{
334 struct gpiod_data *data = dev_get_drvdata(dev);
335 ssize_t status;
336 long value;
337
338 status = kstrtol(s: buf, base: 0, res: &value);
339 if (status)
340 return status;
341
342 mutex_lock(&data->mutex);
343
344 status = gpio_sysfs_set_active_low(dev, value);
345
346 mutex_unlock(lock: &data->mutex);
347
348 return status ? : size;
349}
350static DEVICE_ATTR_RW(active_low);
351
352static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr,
353 int n)
354{
355 struct device *dev = kobj_to_dev(kobj);
356 struct gpiod_data *data = dev_get_drvdata(dev);
357 struct gpio_desc *desc = data->desc;
358 umode_t mode = attr->mode;
359 bool show_direction = data->direction_can_change;
360
361 if (attr == &dev_attr_direction.attr) {
362 if (!show_direction)
363 mode = 0;
364 } else if (attr == &dev_attr_edge.attr) {
365 if (gpiod_to_irq(desc) < 0)
366 mode = 0;
367 if (!show_direction && test_bit(FLAG_IS_OUT, &desc->flags))
368 mode = 0;
369 }
370
371 return mode;
372}
373
374static struct attribute *gpio_attrs[] = {
375 &dev_attr_direction.attr,
376 &dev_attr_edge.attr,
377 &dev_attr_value.attr,
378 &dev_attr_active_low.attr,
379 NULL,
380};
381
382static const struct attribute_group gpio_group = {
383 .attrs = gpio_attrs,
384 .is_visible = gpio_is_visible,
385};
386
387static const struct attribute_group *gpio_groups[] = {
388 &gpio_group,
389 NULL
390};
391
392/*
393 * /sys/class/gpio/gpiochipN/
394 * /base ... matching gpio_chip.base (N)
395 * /label ... matching gpio_chip.label
396 * /ngpio ... matching gpio_chip.ngpio
397 */
398
399static ssize_t base_show(struct device *dev,
400 struct device_attribute *attr, char *buf)
401{
402 const struct gpio_chip *chip = dev_get_drvdata(dev);
403
404 return sysfs_emit(buf, fmt: "%d\n", chip->base);
405}
406static DEVICE_ATTR_RO(base);
407
408static ssize_t label_show(struct device *dev,
409 struct device_attribute *attr, char *buf)
410{
411 const struct gpio_chip *chip = dev_get_drvdata(dev);
412
413 return sysfs_emit(buf, fmt: "%s\n", chip->label ?: "");
414}
415static DEVICE_ATTR_RO(label);
416
417static ssize_t ngpio_show(struct device *dev,
418 struct device_attribute *attr, char *buf)
419{
420 const struct gpio_chip *chip = dev_get_drvdata(dev);
421
422 return sysfs_emit(buf, fmt: "%u\n", chip->ngpio);
423}
424static DEVICE_ATTR_RO(ngpio);
425
426static struct attribute *gpiochip_attrs[] = {
427 &dev_attr_base.attr,
428 &dev_attr_label.attr,
429 &dev_attr_ngpio.attr,
430 NULL,
431};
432ATTRIBUTE_GROUPS(gpiochip);
433
434/*
435 * /sys/class/gpio/export ... write-only
436 * integer N ... number of GPIO to export (full access)
437 * /sys/class/gpio/unexport ... write-only
438 * integer N ... number of GPIO to unexport
439 */
440static ssize_t export_store(const struct class *class,
441 const struct class_attribute *attr,
442 const char *buf, size_t len)
443{
444 long gpio;
445 struct gpio_desc *desc;
446 int status;
447 struct gpio_chip *gc;
448 int offset;
449
450 status = kstrtol(s: buf, base: 0, res: &gpio);
451 if (status < 0)
452 goto done;
453
454 desc = gpio_to_desc(gpio);
455 /* reject invalid GPIOs */
456 if (!desc) {
457 pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
458 return -EINVAL;
459 }
460 gc = desc->gdev->chip;
461 offset = gpio_chip_hwgpio(desc);
462 if (!gpiochip_line_is_valid(gc, offset)) {
463 pr_warn("%s: GPIO %ld masked\n", __func__, gpio);
464 return -EINVAL;
465 }
466
467 /* No extra locking here; FLAG_SYSFS just signifies that the
468 * request and export were done by on behalf of userspace, so
469 * they may be undone on its behalf too.
470 */
471
472 status = gpiod_request_user(desc, label: "sysfs");
473 if (status)
474 goto done;
475
476 status = gpiod_set_transitory(desc, transitory: false);
477 if (!status) {
478 status = gpiod_export(desc, direction_may_change: true);
479 if (status < 0)
480 gpiod_free(desc);
481 else
482 set_bit(FLAG_SYSFS, addr: &desc->flags);
483 }
484
485done:
486 if (status)
487 pr_debug("%s: status %d\n", __func__, status);
488 return status ? : len;
489}
490static CLASS_ATTR_WO(export);
491
492static ssize_t unexport_store(const struct class *class,
493 const struct class_attribute *attr,
494 const char *buf, size_t len)
495{
496 long gpio;
497 struct gpio_desc *desc;
498 int status;
499
500 status = kstrtol(s: buf, base: 0, res: &gpio);
501 if (status < 0)
502 goto done;
503
504 desc = gpio_to_desc(gpio);
505 /* reject bogus commands (gpiod_unexport() ignores them) */
506 if (!desc) {
507 pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
508 return -EINVAL;
509 }
510
511 status = -EINVAL;
512
513 /* No extra locking here; FLAG_SYSFS just signifies that the
514 * request and export were done by on behalf of userspace, so
515 * they may be undone on its behalf too.
516 */
517 if (test_and_clear_bit(FLAG_SYSFS, addr: &desc->flags)) {
518 gpiod_unexport(desc);
519 gpiod_free(desc);
520 status = 0;
521 }
522done:
523 if (status)
524 pr_debug("%s: status %d\n", __func__, status);
525 return status ? : len;
526}
527static CLASS_ATTR_WO(unexport);
528
529static struct attribute *gpio_class_attrs[] = {
530 &class_attr_export.attr,
531 &class_attr_unexport.attr,
532 NULL,
533};
534ATTRIBUTE_GROUPS(gpio_class);
535
536static struct class gpio_class = {
537 .name = "gpio",
538 .class_groups = gpio_class_groups,
539};
540
541
542/**
543 * gpiod_export - export a GPIO through sysfs
544 * @desc: GPIO to make available, already requested
545 * @direction_may_change: true if userspace may change GPIO direction
546 * Context: arch_initcall or later
547 *
548 * When drivers want to make a GPIO accessible to userspace after they
549 * have requested it -- perhaps while debugging, or as part of their
550 * public interface -- they may use this routine. If the GPIO can
551 * change direction (some can't) and the caller allows it, userspace
552 * will see "direction" sysfs attribute which may be used to change
553 * the gpio's direction. A "value" attribute will always be provided.
554 *
555 * Returns zero on success, else an error.
556 */
557int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
558{
559 struct gpio_chip *chip;
560 struct gpio_device *gdev;
561 struct gpiod_data *data;
562 unsigned long flags;
563 int status;
564 const char *ioname = NULL;
565 struct device *dev;
566 int offset;
567
568 /* can't export until sysfs is available ... */
569 if (!class_is_registered(class: &gpio_class)) {
570 pr_debug("%s: called too early!\n", __func__);
571 return -ENOENT;
572 }
573
574 if (!desc) {
575 pr_debug("%s: invalid gpio descriptor\n", __func__);
576 return -EINVAL;
577 }
578
579 gdev = desc->gdev;
580 chip = gdev->chip;
581
582 mutex_lock(&sysfs_lock);
583
584 /* check if chip is being removed */
585 if (!chip || !gdev->mockdev) {
586 status = -ENODEV;
587 goto err_unlock;
588 }
589
590 spin_lock_irqsave(&gpio_lock, flags);
591 if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
592 test_bit(FLAG_EXPORT, &desc->flags)) {
593 spin_unlock_irqrestore(lock: &gpio_lock, flags);
594 gpiod_dbg(desc, "%s: unavailable (requested=%d, exported=%d)\n",
595 __func__,
596 test_bit(FLAG_REQUESTED, &desc->flags),
597 test_bit(FLAG_EXPORT, &desc->flags));
598 status = -EPERM;
599 goto err_unlock;
600 }
601 spin_unlock_irqrestore(lock: &gpio_lock, flags);
602
603 data = kzalloc(size: sizeof(*data), GFP_KERNEL);
604 if (!data) {
605 status = -ENOMEM;
606 goto err_unlock;
607 }
608
609 data->desc = desc;
610 mutex_init(&data->mutex);
611 if (chip->direction_input && chip->direction_output)
612 data->direction_can_change = direction_may_change;
613 else
614 data->direction_can_change = false;
615
616 offset = gpio_chip_hwgpio(desc);
617 if (chip->names && chip->names[offset])
618 ioname = chip->names[offset];
619
620 dev = device_create_with_groups(cls: &gpio_class, parent: &gdev->dev,
621 MKDEV(0, 0), drvdata: data, groups: gpio_groups,
622 fmt: ioname ? ioname : "gpio%u",
623 desc_to_gpio(desc));
624 if (IS_ERR(ptr: dev)) {
625 status = PTR_ERR(ptr: dev);
626 goto err_free_data;
627 }
628
629 set_bit(FLAG_EXPORT, addr: &desc->flags);
630 mutex_unlock(lock: &sysfs_lock);
631 return 0;
632
633err_free_data:
634 kfree(objp: data);
635err_unlock:
636 mutex_unlock(lock: &sysfs_lock);
637 gpiod_dbg(desc, "%s: status %d\n", __func__, status);
638 return status;
639}
640EXPORT_SYMBOL_GPL(gpiod_export);
641
642static int match_export(struct device *dev, const void *desc)
643{
644 struct gpiod_data *data = dev_get_drvdata(dev);
645
646 return data->desc == desc;
647}
648
649/**
650 * gpiod_export_link - create a sysfs link to an exported GPIO node
651 * @dev: device under which to create symlink
652 * @name: name of the symlink
653 * @desc: GPIO to create symlink to, already exported
654 *
655 * Set up a symlink from /sys/.../dev/name to /sys/class/gpio/gpioN
656 * node. Caller is responsible for unlinking.
657 *
658 * Returns zero on success, else an error.
659 */
660int gpiod_export_link(struct device *dev, const char *name,
661 struct gpio_desc *desc)
662{
663 struct device *cdev;
664 int ret;
665
666 if (!desc) {
667 pr_warn("%s: invalid GPIO\n", __func__);
668 return -EINVAL;
669 }
670
671 cdev = class_find_device(class: &gpio_class, NULL, data: desc, match: match_export);
672 if (!cdev)
673 return -ENODEV;
674
675 ret = sysfs_create_link(kobj: &dev->kobj, target: &cdev->kobj, name);
676 put_device(dev: cdev);
677
678 return ret;
679}
680EXPORT_SYMBOL_GPL(gpiod_export_link);
681
682/**
683 * gpiod_unexport - reverse effect of gpiod_export()
684 * @desc: GPIO to make unavailable
685 *
686 * This is implicit on gpiod_free().
687 */
688void gpiod_unexport(struct gpio_desc *desc)
689{
690 struct gpiod_data *data;
691 struct device *dev;
692
693 if (!desc) {
694 pr_warn("%s: invalid GPIO\n", __func__);
695 return;
696 }
697
698 mutex_lock(&sysfs_lock);
699
700 if (!test_bit(FLAG_EXPORT, &desc->flags))
701 goto err_unlock;
702
703 dev = class_find_device(class: &gpio_class, NULL, data: desc, match: match_export);
704 if (!dev)
705 goto err_unlock;
706
707 data = dev_get_drvdata(dev);
708
709 clear_bit(FLAG_EXPORT, addr: &desc->flags);
710
711 device_unregister(dev);
712
713 /*
714 * Release irq after deregistration to prevent race with edge_store.
715 */
716 if (data->irq_flags)
717 gpio_sysfs_free_irq(dev);
718
719 mutex_unlock(lock: &sysfs_lock);
720
721 put_device(dev);
722 kfree(objp: data);
723
724 return;
725
726err_unlock:
727 mutex_unlock(lock: &sysfs_lock);
728}
729EXPORT_SYMBOL_GPL(gpiod_unexport);
730
731int gpiochip_sysfs_register(struct gpio_device *gdev)
732{
733 struct device *dev;
734 struct device *parent;
735 struct gpio_chip *chip = gdev->chip;
736
737 /*
738 * Many systems add gpio chips for SOC support very early,
739 * before driver model support is available. In those cases we
740 * register later, in gpiolib_sysfs_init() ... here we just
741 * verify that _some_ field of gpio_class got initialized.
742 */
743 if (!class_is_registered(class: &gpio_class))
744 return 0;
745
746 /*
747 * For sysfs backward compatibility we need to preserve this
748 * preferred parenting to the gpio_chip parent field, if set.
749 */
750 if (chip->parent)
751 parent = chip->parent;
752 else
753 parent = &gdev->dev;
754
755 /* use chip->base for the ID; it's already known to be unique */
756 dev = device_create_with_groups(cls: &gpio_class, parent, MKDEV(0, 0), drvdata: chip,
757 groups: gpiochip_groups, GPIOCHIP_NAME "%d",
758 chip->base);
759 if (IS_ERR(ptr: dev))
760 return PTR_ERR(ptr: dev);
761
762 mutex_lock(&sysfs_lock);
763 gdev->mockdev = dev;
764 mutex_unlock(lock: &sysfs_lock);
765
766 return 0;
767}
768
769void gpiochip_sysfs_unregister(struct gpio_device *gdev)
770{
771 struct gpio_desc *desc;
772 struct gpio_chip *chip = gdev->chip;
773
774 if (!gdev->mockdev)
775 return;
776
777 device_unregister(dev: gdev->mockdev);
778
779 /* prevent further gpiod exports */
780 mutex_lock(&sysfs_lock);
781 gdev->mockdev = NULL;
782 mutex_unlock(lock: &sysfs_lock);
783
784 /* unregister gpiod class devices owned by sysfs */
785 for_each_gpio_desc_with_flag(chip, desc, FLAG_SYSFS) {
786 gpiod_unexport(desc);
787 gpiod_free(desc);
788 }
789}
790
791static int __init gpiolib_sysfs_init(void)
792{
793 int status;
794 unsigned long flags;
795 struct gpio_device *gdev;
796
797 status = class_register(class: &gpio_class);
798 if (status < 0)
799 return status;
800
801 /* Scan and register the gpio_chips which registered very
802 * early (e.g. before the class_register above was called).
803 *
804 * We run before arch_initcall() so chip->dev nodes can have
805 * registered, and so arch_initcall() can always gpiod_export().
806 */
807 spin_lock_irqsave(&gpio_lock, flags);
808 list_for_each_entry(gdev, &gpio_devices, list) {
809 if (gdev->mockdev)
810 continue;
811
812 /*
813 * TODO we yield gpio_lock here because
814 * gpiochip_sysfs_register() acquires a mutex. This is unsafe
815 * and needs to be fixed.
816 *
817 * Also it would be nice to use gpio_device_find() here so we
818 * can keep gpio_chips local to gpiolib.c, but the yield of
819 * gpio_lock prevents us from doing this.
820 */
821 spin_unlock_irqrestore(lock: &gpio_lock, flags);
822 status = gpiochip_sysfs_register(gdev);
823 spin_lock_irqsave(&gpio_lock, flags);
824 }
825 spin_unlock_irqrestore(lock: &gpio_lock, flags);
826
827 return status;
828}
829postcore_initcall(gpiolib_sysfs_init);
830

source code of linux/drivers/gpio/gpiolib-sysfs.c