xref: /openbmc/linux/drivers/gpio/gpiolib-sysfs.c (revision 6aa7de05)
1 #include <linux/idr.h>
2 #include <linux/mutex.h>
3 #include <linux/device.h>
4 #include <linux/sysfs.h>
5 #include <linux/gpio.h>
6 #include <linux/gpio/consumer.h>
7 #include <linux/gpio/driver.h>
8 #include <linux/interrupt.h>
9 #include <linux/kdev_t.h>
10 #include <linux/slab.h>
11 
12 #include "gpiolib.h"
13 
14 #define GPIO_IRQF_TRIGGER_FALLING	BIT(0)
15 #define GPIO_IRQF_TRIGGER_RISING	BIT(1)
16 #define GPIO_IRQF_TRIGGER_BOTH		(GPIO_IRQF_TRIGGER_FALLING | \
17 					 GPIO_IRQF_TRIGGER_RISING)
18 
19 struct gpiod_data {
20 	struct gpio_desc *desc;
21 
22 	struct mutex mutex;
23 	struct kernfs_node *value_kn;
24 	int irq;
25 	unsigned char irq_flags;
26 
27 	bool direction_can_change;
28 };
29 
30 /*
31  * Lock to serialise gpiod export and unexport, and prevent re-export of
32  * gpiod whose chip is being unregistered.
33  */
34 static DEFINE_MUTEX(sysfs_lock);
35 
36 /*
37  * /sys/class/gpio/gpioN... only for GPIOs that are exported
38  *   /direction
39  *      * MAY BE OMITTED if kernel won't allow direction changes
40  *      * is read/write as "in" or "out"
41  *      * may also be written as "high" or "low", initializing
42  *        output value as specified ("out" implies "low")
43  *   /value
44  *      * always readable, subject to hardware behavior
45  *      * may be writable, as zero/nonzero
46  *   /edge
47  *      * configures behavior of poll(2) on /value
48  *      * available only if pin can generate IRQs on input
49  *      * is read/write as "none", "falling", "rising", or "both"
50  *   /active_low
51  *      * configures polarity of /value
52  *      * is read/write as zero/nonzero
53  *      * also affects existing and subsequent "falling" and "rising"
54  *        /edge configuration
55  */
56 
57 static ssize_t direction_show(struct device *dev,
58 		struct device_attribute *attr, char *buf)
59 {
60 	struct gpiod_data *data = dev_get_drvdata(dev);
61 	struct gpio_desc *desc = data->desc;
62 	ssize_t			status;
63 
64 	mutex_lock(&data->mutex);
65 
66 	gpiod_get_direction(desc);
67 	status = sprintf(buf, "%s\n",
68 			test_bit(FLAG_IS_OUT, &desc->flags)
69 				? "out" : "in");
70 
71 	mutex_unlock(&data->mutex);
72 
73 	return status;
74 }
75 
76 static ssize_t direction_store(struct device *dev,
77 		struct device_attribute *attr, const char *buf, size_t size)
78 {
79 	struct gpiod_data *data = dev_get_drvdata(dev);
80 	struct gpio_desc *desc = data->desc;
81 	ssize_t			status;
82 
83 	mutex_lock(&data->mutex);
84 
85 	if (sysfs_streq(buf, "high"))
86 		status = gpiod_direction_output_raw(desc, 1);
87 	else if (sysfs_streq(buf, "out") || sysfs_streq(buf, "low"))
88 		status = gpiod_direction_output_raw(desc, 0);
89 	else if (sysfs_streq(buf, "in"))
90 		status = gpiod_direction_input(desc);
91 	else
92 		status = -EINVAL;
93 
94 	mutex_unlock(&data->mutex);
95 
96 	return status ? : size;
97 }
98 static DEVICE_ATTR_RW(direction);
99 
100 static ssize_t value_show(struct device *dev,
101 		struct device_attribute *attr, char *buf)
102 {
103 	struct gpiod_data *data = dev_get_drvdata(dev);
104 	struct gpio_desc *desc = data->desc;
105 	ssize_t			status;
106 
107 	mutex_lock(&data->mutex);
108 
109 	status = sprintf(buf, "%d\n", gpiod_get_value_cansleep(desc));
110 
111 	mutex_unlock(&data->mutex);
112 
113 	return status;
114 }
115 
116 static ssize_t value_store(struct device *dev,
117 		struct device_attribute *attr, const char *buf, size_t size)
118 {
119 	struct gpiod_data *data = dev_get_drvdata(dev);
120 	struct gpio_desc *desc = data->desc;
121 	ssize_t			status;
122 
123 	mutex_lock(&data->mutex);
124 
125 	if (!test_bit(FLAG_IS_OUT, &desc->flags)) {
126 		status = -EPERM;
127 	} else {
128 		long		value;
129 
130 		status = kstrtol(buf, 0, &value);
131 		if (status == 0) {
132 			gpiod_set_value_cansleep(desc, value);
133 			status = size;
134 		}
135 	}
136 
137 	mutex_unlock(&data->mutex);
138 
139 	return status;
140 }
141 static DEVICE_ATTR_RW(value);
142 
143 static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
144 {
145 	struct gpiod_data *data = priv;
146 
147 	sysfs_notify_dirent(data->value_kn);
148 
149 	return IRQ_HANDLED;
150 }
151 
152 /* Caller holds gpiod-data mutex. */
153 static int gpio_sysfs_request_irq(struct device *dev, unsigned char flags)
154 {
155 	struct gpiod_data	*data = dev_get_drvdata(dev);
156 	struct gpio_desc	*desc = data->desc;
157 	unsigned long		irq_flags;
158 	int			ret;
159 
160 	data->irq = gpiod_to_irq(desc);
161 	if (data->irq < 0)
162 		return -EIO;
163 
164 	data->value_kn = sysfs_get_dirent(dev->kobj.sd, "value");
165 	if (!data->value_kn)
166 		return -ENODEV;
167 
168 	irq_flags = IRQF_SHARED;
169 	if (flags & GPIO_IRQF_TRIGGER_FALLING)
170 		irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
171 			IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING;
172 	if (flags & GPIO_IRQF_TRIGGER_RISING)
173 		irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
174 			IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
175 
176 	/*
177 	 * FIXME: This should be done in the irq_request_resources callback
178 	 *        when the irq is requested, but a few drivers currently fail
179 	 *        to do so.
180 	 *
181 	 *        Remove this redundant call (along with the corresponding
182 	 *        unlock) when those drivers have been fixed.
183 	 */
184 	ret = gpiochip_lock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc));
185 	if (ret < 0)
186 		goto err_put_kn;
187 
188 	ret = request_any_context_irq(data->irq, gpio_sysfs_irq, irq_flags,
189 				"gpiolib", data);
190 	if (ret < 0)
191 		goto err_unlock;
192 
193 	data->irq_flags = flags;
194 
195 	return 0;
196 
197 err_unlock:
198 	gpiochip_unlock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc));
199 err_put_kn:
200 	sysfs_put(data->value_kn);
201 
202 	return ret;
203 }
204 
205 /*
206  * Caller holds gpiod-data mutex (unless called after class-device
207  * deregistration).
208  */
209 static void gpio_sysfs_free_irq(struct device *dev)
210 {
211 	struct gpiod_data *data = dev_get_drvdata(dev);
212 	struct gpio_desc *desc = data->desc;
213 
214 	data->irq_flags = 0;
215 	free_irq(data->irq, data);
216 	gpiochip_unlock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc));
217 	sysfs_put(data->value_kn);
218 }
219 
220 static const struct {
221 	const char *name;
222 	unsigned char flags;
223 } trigger_types[] = {
224 	{ "none",    0 },
225 	{ "falling", GPIO_IRQF_TRIGGER_FALLING },
226 	{ "rising",  GPIO_IRQF_TRIGGER_RISING },
227 	{ "both",    GPIO_IRQF_TRIGGER_BOTH },
228 };
229 
230 static ssize_t edge_show(struct device *dev,
231 		struct device_attribute *attr, char *buf)
232 {
233 	struct gpiod_data *data = dev_get_drvdata(dev);
234 	ssize_t	status = 0;
235 	int i;
236 
237 	mutex_lock(&data->mutex);
238 
239 	for (i = 0; i < ARRAY_SIZE(trigger_types); i++) {
240 		if (data->irq_flags == trigger_types[i].flags) {
241 			status = sprintf(buf, "%s\n", trigger_types[i].name);
242 			break;
243 		}
244 	}
245 
246 	mutex_unlock(&data->mutex);
247 
248 	return status;
249 }
250 
251 static ssize_t edge_store(struct device *dev,
252 		struct device_attribute *attr, const char *buf, size_t size)
253 {
254 	struct gpiod_data *data = dev_get_drvdata(dev);
255 	unsigned char flags;
256 	ssize_t	status = size;
257 	int i;
258 
259 	for (i = 0; i < ARRAY_SIZE(trigger_types); i++) {
260 		if (sysfs_streq(trigger_types[i].name, buf))
261 			break;
262 	}
263 
264 	if (i == ARRAY_SIZE(trigger_types))
265 		return -EINVAL;
266 
267 	flags = trigger_types[i].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 
285 out_unlock:
286 	mutex_unlock(&data->mutex);
287 
288 	return status;
289 }
290 static DEVICE_ATTR_RW(edge);
291 
292 /* Caller holds gpiod-data mutex. */
293 static 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 	if (value)
304 		set_bit(FLAG_ACTIVE_LOW, &desc->flags);
305 	else
306 		clear_bit(FLAG_ACTIVE_LOW, &desc->flags);
307 
308 	/* reconfigure poll(2) support if enabled on one edge only */
309 	if (flags == GPIO_IRQF_TRIGGER_FALLING ||
310 					flags == GPIO_IRQF_TRIGGER_RISING) {
311 		gpio_sysfs_free_irq(dev);
312 		status = gpio_sysfs_request_irq(dev, flags);
313 	}
314 
315 	return status;
316 }
317 
318 static ssize_t active_low_show(struct device *dev,
319 		struct device_attribute *attr, char *buf)
320 {
321 	struct gpiod_data *data = dev_get_drvdata(dev);
322 	struct gpio_desc *desc = data->desc;
323 	ssize_t			status;
324 
325 	mutex_lock(&data->mutex);
326 
327 	status = sprintf(buf, "%d\n",
328 				!!test_bit(FLAG_ACTIVE_LOW, &desc->flags));
329 
330 	mutex_unlock(&data->mutex);
331 
332 	return status;
333 }
334 
335 static ssize_t active_low_store(struct device *dev,
336 		struct device_attribute *attr, const char *buf, size_t size)
337 {
338 	struct gpiod_data	*data = dev_get_drvdata(dev);
339 	ssize_t			status;
340 	long			value;
341 
342 	mutex_lock(&data->mutex);
343 
344 	status = kstrtol(buf, 0, &value);
345 	if (status == 0)
346 		status = gpio_sysfs_set_active_low(dev, value);
347 
348 	mutex_unlock(&data->mutex);
349 
350 	return status ? : size;
351 }
352 static DEVICE_ATTR_RW(active_low);
353 
354 static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr,
355 			       int n)
356 {
357 	struct device *dev = container_of(kobj, struct device, kobj);
358 	struct gpiod_data *data = dev_get_drvdata(dev);
359 	struct gpio_desc *desc = data->desc;
360 	umode_t mode = attr->mode;
361 	bool show_direction = data->direction_can_change;
362 
363 	if (attr == &dev_attr_direction.attr) {
364 		if (!show_direction)
365 			mode = 0;
366 	} else if (attr == &dev_attr_edge.attr) {
367 		if (gpiod_to_irq(desc) < 0)
368 			mode = 0;
369 		if (!show_direction && test_bit(FLAG_IS_OUT, &desc->flags))
370 			mode = 0;
371 	}
372 
373 	return mode;
374 }
375 
376 static struct attribute *gpio_attrs[] = {
377 	&dev_attr_direction.attr,
378 	&dev_attr_edge.attr,
379 	&dev_attr_value.attr,
380 	&dev_attr_active_low.attr,
381 	NULL,
382 };
383 
384 static const struct attribute_group gpio_group = {
385 	.attrs = gpio_attrs,
386 	.is_visible = gpio_is_visible,
387 };
388 
389 static const struct attribute_group *gpio_groups[] = {
390 	&gpio_group,
391 	NULL
392 };
393 
394 /*
395  * /sys/class/gpio/gpiochipN/
396  *   /base ... matching gpio_chip.base (N)
397  *   /label ... matching gpio_chip.label
398  *   /ngpio ... matching gpio_chip.ngpio
399  */
400 
401 static ssize_t base_show(struct device *dev,
402 			       struct device_attribute *attr, char *buf)
403 {
404 	const struct gpio_chip	*chip = dev_get_drvdata(dev);
405 
406 	return sprintf(buf, "%d\n", chip->base);
407 }
408 static DEVICE_ATTR_RO(base);
409 
410 static ssize_t label_show(struct device *dev,
411 			       struct device_attribute *attr, char *buf)
412 {
413 	const struct gpio_chip	*chip = dev_get_drvdata(dev);
414 
415 	return sprintf(buf, "%s\n", chip->label ? : "");
416 }
417 static DEVICE_ATTR_RO(label);
418 
419 static ssize_t ngpio_show(struct device *dev,
420 			       struct device_attribute *attr, char *buf)
421 {
422 	const struct gpio_chip	*chip = dev_get_drvdata(dev);
423 
424 	return sprintf(buf, "%u\n", chip->ngpio);
425 }
426 static DEVICE_ATTR_RO(ngpio);
427 
428 static struct attribute *gpiochip_attrs[] = {
429 	&dev_attr_base.attr,
430 	&dev_attr_label.attr,
431 	&dev_attr_ngpio.attr,
432 	NULL,
433 };
434 ATTRIBUTE_GROUPS(gpiochip);
435 
436 static struct gpio_desc *gpio_to_valid_desc(int gpio)
437 {
438 	return gpio_is_valid(gpio) ? gpio_to_desc(gpio) : NULL;
439 }
440 
441 /*
442  * /sys/class/gpio/export ... write-only
443  *	integer N ... number of GPIO to export (full access)
444  * /sys/class/gpio/unexport ... write-only
445  *	integer N ... number of GPIO to unexport
446  */
447 static ssize_t export_store(struct class *class,
448 				struct class_attribute *attr,
449 				const char *buf, size_t len)
450 {
451 	long			gpio;
452 	struct gpio_desc	*desc;
453 	int			status;
454 
455 	status = kstrtol(buf, 0, &gpio);
456 	if (status < 0)
457 		goto done;
458 
459 	desc = gpio_to_valid_desc(gpio);
460 	/* reject invalid GPIOs */
461 	if (!desc) {
462 		pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
463 		return -EINVAL;
464 	}
465 
466 	/* No extra locking here; FLAG_SYSFS just signifies that the
467 	 * request and export were done by on behalf of userspace, so
468 	 * they may be undone on its behalf too.
469 	 */
470 
471 	status = gpiod_request(desc, "sysfs");
472 	if (status < 0) {
473 		if (status == -EPROBE_DEFER)
474 			status = -ENODEV;
475 		goto done;
476 	}
477 	status = gpiod_export(desc, true);
478 	if (status < 0)
479 		gpiod_free(desc);
480 	else
481 		set_bit(FLAG_SYSFS, &desc->flags);
482 
483 done:
484 	if (status)
485 		pr_debug("%s: status %d\n", __func__, status);
486 	return status ? : len;
487 }
488 static CLASS_ATTR_WO(export);
489 
490 static ssize_t unexport_store(struct class *class,
491 				struct class_attribute *attr,
492 				const char *buf, size_t len)
493 {
494 	long			gpio;
495 	struct gpio_desc	*desc;
496 	int			status;
497 
498 	status = kstrtol(buf, 0, &gpio);
499 	if (status < 0)
500 		goto done;
501 
502 	desc = gpio_to_valid_desc(gpio);
503 	/* reject bogus commands (gpio_unexport ignores them) */
504 	if (!desc) {
505 		pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
506 		return -EINVAL;
507 	}
508 
509 	status = -EINVAL;
510 
511 	/* No extra locking here; FLAG_SYSFS just signifies that the
512 	 * request and export were done by on behalf of userspace, so
513 	 * they may be undone on its behalf too.
514 	 */
515 	if (test_and_clear_bit(FLAG_SYSFS, &desc->flags)) {
516 		status = 0;
517 		gpiod_free(desc);
518 	}
519 done:
520 	if (status)
521 		pr_debug("%s: status %d\n", __func__, status);
522 	return status ? : len;
523 }
524 static CLASS_ATTR_WO(unexport);
525 
526 static struct attribute *gpio_class_attrs[] = {
527 	&class_attr_export.attr,
528 	&class_attr_unexport.attr,
529 	NULL,
530 };
531 ATTRIBUTE_GROUPS(gpio_class);
532 
533 static struct class gpio_class = {
534 	.name =		"gpio",
535 	.owner =	THIS_MODULE,
536 
537 	.class_groups = gpio_class_groups,
538 };
539 
540 
541 /**
542  * gpiod_export - export a GPIO through sysfs
543  * @desc: GPIO to make available, already requested
544  * @direction_may_change: true if userspace may change GPIO direction
545  * Context: arch_initcall or later
546  *
547  * When drivers want to make a GPIO accessible to userspace after they
548  * have requested it -- perhaps while debugging, or as part of their
549  * public interface -- they may use this routine.  If the GPIO can
550  * change direction (some can't) and the caller allows it, userspace
551  * will see "direction" sysfs attribute which may be used to change
552  * the gpio's direction.  A "value" attribute will always be provided.
553  *
554  * Returns zero on success, else an error.
555  */
556 int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
557 {
558 	struct gpio_chip	*chip;
559 	struct gpio_device	*gdev;
560 	struct gpiod_data	*data;
561 	unsigned long		flags;
562 	int			status;
563 	const char		*ioname = NULL;
564 	struct device		*dev;
565 	int			offset;
566 
567 	/* can't export until sysfs is available ... */
568 	if (!gpio_class.p) {
569 		pr_debug("%s: called too early!\n", __func__);
570 		return -ENOENT;
571 	}
572 
573 	if (!desc) {
574 		pr_debug("%s: invalid gpio descriptor\n", __func__);
575 		return -EINVAL;
576 	}
577 
578 	gdev = desc->gdev;
579 	chip = gdev->chip;
580 
581 	mutex_lock(&sysfs_lock);
582 
583 	/* check if chip is being removed */
584 	if (!chip || !gdev->mockdev) {
585 		status = -ENODEV;
586 		goto err_unlock;
587 	}
588 
589 	spin_lock_irqsave(&gpio_lock, flags);
590 	if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
591 	     test_bit(FLAG_EXPORT, &desc->flags)) {
592 		spin_unlock_irqrestore(&gpio_lock, flags);
593 		gpiod_dbg(desc, "%s: unavailable (requested=%d, exported=%d)\n",
594 				__func__,
595 				test_bit(FLAG_REQUESTED, &desc->flags),
596 				test_bit(FLAG_EXPORT, &desc->flags));
597 		status = -EPERM;
598 		goto err_unlock;
599 	}
600 	spin_unlock_irqrestore(&gpio_lock, flags);
601 
602 	data = kzalloc(sizeof(*data), GFP_KERNEL);
603 	if (!data) {
604 		status = -ENOMEM;
605 		goto err_unlock;
606 	}
607 
608 	data->desc = desc;
609 	mutex_init(&data->mutex);
610 	if (chip->direction_input && chip->direction_output)
611 		data->direction_can_change = direction_may_change;
612 	else
613 		data->direction_can_change = false;
614 
615 	offset = gpio_chip_hwgpio(desc);
616 	if (chip->names && chip->names[offset])
617 		ioname = chip->names[offset];
618 
619 	dev = device_create_with_groups(&gpio_class, &gdev->dev,
620 					MKDEV(0, 0), data, gpio_groups,
621 					ioname ? ioname : "gpio%u",
622 					desc_to_gpio(desc));
623 	if (IS_ERR(dev)) {
624 		status = PTR_ERR(dev);
625 		goto err_free_data;
626 	}
627 
628 	set_bit(FLAG_EXPORT, &desc->flags);
629 	mutex_unlock(&sysfs_lock);
630 	return 0;
631 
632 err_free_data:
633 	kfree(data);
634 err_unlock:
635 	mutex_unlock(&sysfs_lock);
636 	gpiod_dbg(desc, "%s: status %d\n", __func__, status);
637 	return status;
638 }
639 EXPORT_SYMBOL_GPL(gpiod_export);
640 
641 static int match_export(struct device *dev, const void *desc)
642 {
643 	struct gpiod_data *data = dev_get_drvdata(dev);
644 
645 	return data->desc == desc;
646 }
647 
648 /**
649  * gpiod_export_link - create a sysfs link to an exported GPIO node
650  * @dev: device under which to create symlink
651  * @name: name of the symlink
652  * @desc: GPIO to create symlink to, already exported
653  *
654  * Set up a symlink from /sys/.../dev/name to /sys/class/gpio/gpioN
655  * node. Caller is responsible for unlinking.
656  *
657  * Returns zero on success, else an error.
658  */
659 int gpiod_export_link(struct device *dev, const char *name,
660 		      struct gpio_desc *desc)
661 {
662 	struct device *cdev;
663 	int ret;
664 
665 	if (!desc) {
666 		pr_warn("%s: invalid GPIO\n", __func__);
667 		return -EINVAL;
668 	}
669 
670 	cdev = class_find_device(&gpio_class, NULL, desc, match_export);
671 	if (!cdev)
672 		return -ENODEV;
673 
674 	ret = sysfs_create_link(&dev->kobj, &cdev->kobj, name);
675 	put_device(cdev);
676 
677 	return ret;
678 }
679 EXPORT_SYMBOL_GPL(gpiod_export_link);
680 
681 /**
682  * gpiod_unexport - reverse effect of gpiod_export()
683  * @desc: GPIO to make unavailable
684  *
685  * This is implicit on gpiod_free().
686  */
687 void gpiod_unexport(struct gpio_desc *desc)
688 {
689 	struct gpiod_data *data;
690 	struct device *dev;
691 
692 	if (!desc) {
693 		pr_warn("%s: invalid GPIO\n", __func__);
694 		return;
695 	}
696 
697 	mutex_lock(&sysfs_lock);
698 
699 	if (!test_bit(FLAG_EXPORT, &desc->flags))
700 		goto err_unlock;
701 
702 	dev = class_find_device(&gpio_class, NULL, desc, match_export);
703 	if (!dev)
704 		goto err_unlock;
705 
706 	data = dev_get_drvdata(dev);
707 
708 	clear_bit(FLAG_EXPORT, &desc->flags);
709 
710 	device_unregister(dev);
711 
712 	/*
713 	 * Release irq after deregistration to prevent race with edge_store.
714 	 */
715 	if (data->irq_flags)
716 		gpio_sysfs_free_irq(dev);
717 
718 	mutex_unlock(&sysfs_lock);
719 
720 	put_device(dev);
721 	kfree(data);
722 
723 	return;
724 
725 err_unlock:
726 	mutex_unlock(&sysfs_lock);
727 }
728 EXPORT_SYMBOL_GPL(gpiod_unexport);
729 
730 int gpiochip_sysfs_register(struct gpio_device *gdev)
731 {
732 	struct device	*dev;
733 	struct device	*parent;
734 	struct gpio_chip *chip = gdev->chip;
735 
736 	/*
737 	 * Many systems add gpio chips for SOC support very early,
738 	 * before driver model support is available.  In those cases we
739 	 * register later, in gpiolib_sysfs_init() ... here we just
740 	 * verify that _some_ field of gpio_class got initialized.
741 	 */
742 	if (!gpio_class.p)
743 		return 0;
744 
745 	/*
746 	 * For sysfs backward compatibility we need to preserve this
747 	 * preferred parenting to the gpio_chip parent field, if set.
748 	 */
749 	if (chip->parent)
750 		parent = chip->parent;
751 	else
752 		parent = &gdev->dev;
753 
754 	/* use chip->base for the ID; it's already known to be unique */
755 	dev = device_create_with_groups(&gpio_class, parent,
756 					MKDEV(0, 0),
757 					chip, gpiochip_groups,
758 					"gpiochip%d", chip->base);
759 	if (IS_ERR(dev))
760 		return PTR_ERR(dev);
761 
762 	mutex_lock(&sysfs_lock);
763 	gdev->mockdev = dev;
764 	mutex_unlock(&sysfs_lock);
765 
766 	return 0;
767 }
768 
769 void gpiochip_sysfs_unregister(struct gpio_device *gdev)
770 {
771 	struct gpio_desc *desc;
772 	struct gpio_chip *chip = gdev->chip;
773 	unsigned int i;
774 
775 	if (!gdev->mockdev)
776 		return;
777 
778 	device_unregister(gdev->mockdev);
779 
780 	/* prevent further gpiod exports */
781 	mutex_lock(&sysfs_lock);
782 	gdev->mockdev = NULL;
783 	mutex_unlock(&sysfs_lock);
784 
785 	/* unregister gpiod class devices owned by sysfs */
786 	for (i = 0; i < chip->ngpio; i++) {
787 		desc = &gdev->descs[i];
788 		if (test_and_clear_bit(FLAG_SYSFS, &desc->flags))
789 			gpiod_free(desc);
790 	}
791 }
792 
793 static int __init gpiolib_sysfs_init(void)
794 {
795 	int		status;
796 	unsigned long	flags;
797 	struct gpio_device *gdev;
798 
799 	status = class_register(&gpio_class);
800 	if (status < 0)
801 		return status;
802 
803 	/* Scan and register the gpio_chips which registered very
804 	 * early (e.g. before the class_register above was called).
805 	 *
806 	 * We run before arch_initcall() so chip->dev nodes can have
807 	 * registered, and so arch_initcall() can always gpio_export().
808 	 */
809 	spin_lock_irqsave(&gpio_lock, flags);
810 	list_for_each_entry(gdev, &gpio_devices, list) {
811 		if (gdev->mockdev)
812 			continue;
813 
814 		/*
815 		 * TODO we yield gpio_lock here because
816 		 * gpiochip_sysfs_register() acquires a mutex. This is unsafe
817 		 * and needs to be fixed.
818 		 *
819 		 * Also it would be nice to use gpiochip_find() here so we
820 		 * can keep gpio_chips local to gpiolib.c, but the yield of
821 		 * gpio_lock prevents us from doing this.
822 		 */
823 		spin_unlock_irqrestore(&gpio_lock, flags);
824 		status = gpiochip_sysfs_register(gdev);
825 		spin_lock_irqsave(&gpio_lock, flags);
826 	}
827 	spin_unlock_irqrestore(&gpio_lock, flags);
828 
829 	return status;
830 }
831 postcore_initcall(gpiolib_sysfs_init);
832