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1// SPDX-License-Identifier: GPL-2.02 3#include <linux/bitops.h>4#include <linux/cleanup.h>5#include <linux/device.h>6#include <linux/idr.h>7#include <linux/init.h>8#include <linux/interrupt.h>9#include <linux/kdev_t.h>10#include <linux/kstrtox.h>11#include <linux/list.h>12#include <linux/mutex.h>13#include <linux/printk.h>14#include <linux/slab.h>15#include <linux/spinlock.h>16#include <linux/string.h>17#include <linux/srcu.h>18#include <linux/sysfs.h>19#include <linux/types.h>20 21#include <linux/gpio/consumer.h>22#include <linux/gpio/driver.h>23 24#include "gpiolib.h"25#include "gpiolib-sysfs.h"26 27struct kernfs_node;28 29#define GPIO_IRQF_TRIGGER_NONE 030#define GPIO_IRQF_TRIGGER_FALLING BIT(0)31#define GPIO_IRQF_TRIGGER_RISING BIT(1)32#define GPIO_IRQF_TRIGGER_BOTH (GPIO_IRQF_TRIGGER_FALLING | \33 GPIO_IRQF_TRIGGER_RISING)34 35struct gpiod_data {36 struct gpio_desc *desc;37 38 struct mutex mutex;39 struct kernfs_node *value_kn;40 int irq;41 unsigned char irq_flags;42 43 bool direction_can_change;44};45 46/*47 * Lock to serialise gpiod export and unexport, and prevent re-export of48 * gpiod whose chip is being unregistered.49 */50static DEFINE_MUTEX(sysfs_lock);51 52/*53 * /sys/class/gpio/gpioN... only for GPIOs that are exported54 * /direction55 * * MAY BE OMITTED if kernel won't allow direction changes56 * * is read/write as "in" or "out"57 * * may also be written as "high" or "low", initializing58 * output value as specified ("out" implies "low")59 * /value60 * * always readable, subject to hardware behavior61 * * may be writable, as zero/nonzero62 * /edge63 * * configures behavior of poll(2) on /value64 * * available only if pin can generate IRQs on input65 * * is read/write as "none", "falling", "rising", or "both"66 * /active_low67 * * configures polarity of /value68 * * is read/write as zero/nonzero69 * * also affects existing and subsequent "falling" and "rising"70 * /edge configuration71 */72 73static ssize_t direction_show(struct device *dev,74 struct device_attribute *attr, char *buf)75{76 struct gpiod_data *data = dev_get_drvdata(dev);77 struct gpio_desc *desc = data->desc;78 int value;79 80 mutex_lock(&data->mutex);81 82 gpiod_get_direction(desc);83 value = !!test_bit(FLAG_IS_OUT, &desc->flags);84 85 mutex_unlock(&data->mutex);86 87 return sysfs_emit(buf, "%s\n", value ? "out" : "in");88}89 90static ssize_t direction_store(struct device *dev,91 struct device_attribute *attr, const char *buf, size_t size)92{93 struct gpiod_data *data = dev_get_drvdata(dev);94 struct gpio_desc *desc = data->desc;95 ssize_t status;96 97 mutex_lock(&data->mutex);98 99 if (sysfs_streq(buf, "high"))100 status = gpiod_direction_output_raw(desc, 1);101 else if (sysfs_streq(buf, "out") || sysfs_streq(buf, "low"))102 status = gpiod_direction_output_raw(desc, 0);103 else if (sysfs_streq(buf, "in"))104 status = gpiod_direction_input(desc);105 else106 status = -EINVAL;107 108 mutex_unlock(&data->mutex);109 110 return status ? : size;111}112static DEVICE_ATTR_RW(direction);113 114static ssize_t value_show(struct device *dev,115 struct device_attribute *attr, char *buf)116{117 struct gpiod_data *data = dev_get_drvdata(dev);118 struct gpio_desc *desc = data->desc;119 ssize_t status;120 121 mutex_lock(&data->mutex);122 123 status = gpiod_get_value_cansleep(desc);124 125 mutex_unlock(&data->mutex);126 127 if (status < 0)128 return status;129 130 return sysfs_emit(buf, "%zd\n", status);131}132 133static ssize_t value_store(struct device *dev,134 struct device_attribute *attr, const char *buf, size_t size)135{136 struct gpiod_data *data = dev_get_drvdata(dev);137 struct gpio_desc *desc = data->desc;138 ssize_t status;139 long value;140 141 status = kstrtol(buf, 0, &value);142 143 mutex_lock(&data->mutex);144 145 if (!test_bit(FLAG_IS_OUT, &desc->flags)) {146 status = -EPERM;147 } else if (status == 0) {148 gpiod_set_value_cansleep(desc, value);149 status = size;150 }151 152 mutex_unlock(&data->mutex);153 154 return status;155}156static DEVICE_ATTR_PREALLOC(value, S_IWUSR | S_IRUGO, value_show, value_store);157 158static irqreturn_t gpio_sysfs_irq(int irq, void *priv)159{160 struct gpiod_data *data = priv;161 162 sysfs_notify_dirent(data->value_kn);163 164 return IRQ_HANDLED;165}166 167/* Caller holds gpiod-data mutex. */168static int gpio_sysfs_request_irq(struct device *dev, unsigned char flags)169{170 struct gpiod_data *data = dev_get_drvdata(dev);171 struct gpio_desc *desc = data->desc;172 unsigned long irq_flags;173 int ret;174 175 CLASS(gpio_chip_guard, guard)(desc);176 if (!guard.gc)177 return -ENODEV;178 179 data->irq = gpiod_to_irq(desc);180 if (data->irq < 0)181 return -EIO;182 183 data->value_kn = sysfs_get_dirent(dev->kobj.sd, "value");184 if (!data->value_kn)185 return -ENODEV;186 187 irq_flags = IRQF_SHARED;188 if (flags & GPIO_IRQF_TRIGGER_FALLING)189 irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?190 IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING;191 if (flags & GPIO_IRQF_TRIGGER_RISING)192 irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?193 IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;194 195 /*196 * FIXME: This should be done in the irq_request_resources callback197 * when the irq is requested, but a few drivers currently fail198 * to do so.199 *200 * Remove this redundant call (along with the corresponding201 * unlock) when those drivers have been fixed.202 */203 ret = gpiochip_lock_as_irq(guard.gc, gpio_chip_hwgpio(desc));204 if (ret < 0)205 goto err_put_kn;206 207 ret = request_any_context_irq(data->irq, gpio_sysfs_irq, irq_flags,208 "gpiolib", data);209 if (ret < 0)210 goto err_unlock;211 212 data->irq_flags = flags;213 214 return 0;215 216err_unlock:217 gpiochip_unlock_as_irq(guard.gc, gpio_chip_hwgpio(desc));218err_put_kn:219 sysfs_put(data->value_kn);220 221 return ret;222}223 224/*225 * Caller holds gpiod-data mutex (unless called after class-device226 * deregistration).227 */228static void gpio_sysfs_free_irq(struct device *dev)229{230 struct gpiod_data *data = dev_get_drvdata(dev);231 struct gpio_desc *desc = data->desc;232 233 CLASS(gpio_chip_guard, guard)(desc);234 if (!guard.gc)235 return;236 237 data->irq_flags = 0;238 free_irq(data->irq, data);239 gpiochip_unlock_as_irq(guard.gc, gpio_chip_hwgpio(desc));240 sysfs_put(data->value_kn);241}242 243static const char * const trigger_names[] = {244 [GPIO_IRQF_TRIGGER_NONE] = "none",245 [GPIO_IRQF_TRIGGER_FALLING] = "falling",246 [GPIO_IRQF_TRIGGER_RISING] = "rising",247 [GPIO_IRQF_TRIGGER_BOTH] = "both",248};249 250static ssize_t edge_show(struct device *dev,251 struct device_attribute *attr, char *buf)252{253 struct gpiod_data *data = dev_get_drvdata(dev);254 int flags;255 256 mutex_lock(&data->mutex);257 258 flags = data->irq_flags;259 260 mutex_unlock(&data->mutex);261 262 if (flags >= ARRAY_SIZE(trigger_names))263 return 0;264 265 return sysfs_emit(buf, "%s\n", trigger_names[flags]);266}267 268static ssize_t edge_store(struct device *dev,269 struct device_attribute *attr, const char *buf, size_t size)270{271 struct gpiod_data *data = dev_get_drvdata(dev);272 ssize_t status = size;273 int flags;274 275 flags = sysfs_match_string(trigger_names, buf);276 if (flags < 0)277 return flags;278 279 mutex_lock(&data->mutex);280 281 if (flags == data->irq_flags) {282 status = size;283 goto out_unlock;284 }285 286 if (data->irq_flags)287 gpio_sysfs_free_irq(dev);288 289 if (flags) {290 status = gpio_sysfs_request_irq(dev, flags);291 if (!status)292 status = size;293 }294 295out_unlock:296 mutex_unlock(&data->mutex);297 298 return status;299}300static DEVICE_ATTR_RW(edge);301 302/* Caller holds gpiod-data mutex. */303static int gpio_sysfs_set_active_low(struct device *dev, int value)304{305 struct gpiod_data *data = dev_get_drvdata(dev);306 unsigned int flags = data->irq_flags;307 struct gpio_desc *desc = data->desc;308 int status = 0;309 310 311 if (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) == !!value)312 return 0;313 314 assign_bit(FLAG_ACTIVE_LOW, &desc->flags, value);315 316 /* reconfigure poll(2) support if enabled on one edge only */317 if (flags == GPIO_IRQF_TRIGGER_FALLING ||318 flags == GPIO_IRQF_TRIGGER_RISING) {319 gpio_sysfs_free_irq(dev);320 status = gpio_sysfs_request_irq(dev, flags);321 }322 323 return status;324}325 326static ssize_t active_low_show(struct device *dev,327 struct device_attribute *attr, char *buf)328{329 struct gpiod_data *data = dev_get_drvdata(dev);330 struct gpio_desc *desc = data->desc;331 int value;332 333 mutex_lock(&data->mutex);334 335 value = !!test_bit(FLAG_ACTIVE_LOW, &desc->flags);336 337 mutex_unlock(&data->mutex);338 339 return sysfs_emit(buf, "%d\n", value);340}341 342static ssize_t active_low_store(struct device *dev,343 struct device_attribute *attr, const char *buf, size_t size)344{345 struct gpiod_data *data = dev_get_drvdata(dev);346 ssize_t status;347 long value;348 349 status = kstrtol(buf, 0, &value);350 if (status)351 return status;352 353 mutex_lock(&data->mutex);354 355 status = gpio_sysfs_set_active_low(dev, value);356 357 mutex_unlock(&data->mutex);358 359 return status ? : size;360}361static DEVICE_ATTR_RW(active_low);362 363static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr,364 int n)365{366 struct device *dev = kobj_to_dev(kobj);367 struct gpiod_data *data = dev_get_drvdata(dev);368 struct gpio_desc *desc = data->desc;369 umode_t mode = attr->mode;370 bool show_direction = data->direction_can_change;371 372 if (attr == &dev_attr_direction.attr) {373 if (!show_direction)374 mode = 0;375 } else if (attr == &dev_attr_edge.attr) {376 if (gpiod_to_irq(desc) < 0)377 mode = 0;378 if (!show_direction && test_bit(FLAG_IS_OUT, &desc->flags))379 mode = 0;380 }381 382 return mode;383}384 385static struct attribute *gpio_attrs[] = {386 &dev_attr_direction.attr,387 &dev_attr_edge.attr,388 &dev_attr_value.attr,389 &dev_attr_active_low.attr,390 NULL,391};392 393static const struct attribute_group gpio_group = {394 .attrs = gpio_attrs,395 .is_visible = gpio_is_visible,396};397 398static const struct attribute_group *gpio_groups[] = {399 &gpio_group,400 NULL401};402 403/*404 * /sys/class/gpio/gpiochipN/405 * /base ... matching gpio_chip.base (N)406 * /label ... matching gpio_chip.label407 * /ngpio ... matching gpio_chip.ngpio408 */409 410static ssize_t base_show(struct device *dev,411 struct device_attribute *attr, char *buf)412{413 const struct gpio_device *gdev = dev_get_drvdata(dev);414 415 return sysfs_emit(buf, "%u\n", gdev->base);416}417static DEVICE_ATTR_RO(base);418 419static ssize_t label_show(struct device *dev,420 struct device_attribute *attr, char *buf)421{422 const struct gpio_device *gdev = dev_get_drvdata(dev);423 424 return sysfs_emit(buf, "%s\n", gdev->label);425}426static DEVICE_ATTR_RO(label);427 428static ssize_t ngpio_show(struct device *dev,429 struct device_attribute *attr, char *buf)430{431 const struct gpio_device *gdev = dev_get_drvdata(dev);432 433 return sysfs_emit(buf, "%u\n", gdev->ngpio);434}435static DEVICE_ATTR_RO(ngpio);436 437static struct attribute *gpiochip_attrs[] = {438 &dev_attr_base.attr,439 &dev_attr_label.attr,440 &dev_attr_ngpio.attr,441 NULL,442};443ATTRIBUTE_GROUPS(gpiochip);444 445/*446 * /sys/class/gpio/export ... write-only447 * integer N ... number of GPIO to export (full access)448 * /sys/class/gpio/unexport ... write-only449 * integer N ... number of GPIO to unexport450 */451static ssize_t export_store(const struct class *class,452 const struct class_attribute *attr,453 const char *buf, size_t len)454{455 struct gpio_desc *desc;456 int status, offset;457 long gpio;458 459 status = kstrtol(buf, 0, &gpio);460 if (status)461 return status;462 463 desc = gpio_to_desc(gpio);464 /* reject invalid GPIOs */465 if (!desc) {466 pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);467 return -EINVAL;468 }469 470 CLASS(gpio_chip_guard, guard)(desc);471 if (!guard.gc)472 return -ENODEV;473 474 offset = gpio_chip_hwgpio(desc);475 if (!gpiochip_line_is_valid(guard.gc, offset)) {476 pr_warn("%s: GPIO %ld masked\n", __func__, gpio);477 return -EINVAL;478 }479 480 /* No extra locking here; FLAG_SYSFS just signifies that the481 * request and export were done by on behalf of userspace, so482 * they may be undone on its behalf too.483 */484 485 status = gpiod_request_user(desc, "sysfs");486 if (status)487 goto done;488 489 status = gpiod_set_transitory(desc, false);490 if (status) {491 gpiod_free(desc);492 goto done;493 }494 495 status = gpiod_export(desc, true);496 if (status < 0)497 gpiod_free(desc);498 else499 set_bit(FLAG_SYSFS, &desc->flags);500 501done:502 if (status)503 pr_debug("%s: status %d\n", __func__, status);504 return status ? : len;505}506static CLASS_ATTR_WO(export);507 508static ssize_t unexport_store(const struct class *class,509 const struct class_attribute *attr,510 const char *buf, size_t len)511{512 struct gpio_desc *desc;513 int status;514 long gpio;515 516 status = kstrtol(buf, 0, &gpio);517 if (status < 0)518 goto done;519 520 desc = gpio_to_desc(gpio);521 /* reject bogus commands (gpiod_unexport() ignores them) */522 if (!desc) {523 pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);524 return -EINVAL;525 }526 527 status = -EINVAL;528 529 /* No extra locking here; FLAG_SYSFS just signifies that the530 * request and export were done by on behalf of userspace, so531 * they may be undone on its behalf too.532 */533 if (test_and_clear_bit(FLAG_SYSFS, &desc->flags)) {534 gpiod_unexport(desc);535 gpiod_free(desc);536 status = 0;537 }538done:539 if (status)540 pr_debug("%s: status %d\n", __func__, status);541 return status ? : len;542}543static CLASS_ATTR_WO(unexport);544 545static struct attribute *gpio_class_attrs[] = {546 &class_attr_export.attr,547 &class_attr_unexport.attr,548 NULL,549};550ATTRIBUTE_GROUPS(gpio_class);551 552static struct class gpio_class = {553 .name = "gpio",554 .class_groups = gpio_class_groups,555};556 557 558/**559 * gpiod_export - export a GPIO through sysfs560 * @desc: GPIO to make available, already requested561 * @direction_may_change: true if userspace may change GPIO direction562 * Context: arch_initcall or later563 *564 * When drivers want to make a GPIO accessible to userspace after they565 * have requested it -- perhaps while debugging, or as part of their566 * public interface -- they may use this routine. If the GPIO can567 * change direction (some can't) and the caller allows it, userspace568 * will see "direction" sysfs attribute which may be used to change569 * the gpio's direction. A "value" attribute will always be provided.570 *571 * Returns:572 * 0 on success, or negative errno on failure.573 */574int gpiod_export(struct gpio_desc *desc, bool direction_may_change)575{576 const char *ioname = NULL;577 struct gpio_device *gdev;578 struct gpiod_data *data;579 struct device *dev;580 int status, offset;581 582 /* can't export until sysfs is available ... */583 if (!class_is_registered(&gpio_class)) {584 pr_debug("%s: called too early!\n", __func__);585 return -ENOENT;586 }587 588 if (!desc) {589 pr_debug("%s: invalid gpio descriptor\n", __func__);590 return -EINVAL;591 }592 593 CLASS(gpio_chip_guard, guard)(desc);594 if (!guard.gc)595 return -ENODEV;596 597 if (test_and_set_bit(FLAG_EXPORT, &desc->flags))598 return -EPERM;599 600 gdev = desc->gdev;601 602 mutex_lock(&sysfs_lock);603 604 /* check if chip is being removed */605 if (!gdev->mockdev) {606 status = -ENODEV;607 goto err_unlock;608 }609 610 if (!test_bit(FLAG_REQUESTED, &desc->flags)) {611 gpiod_dbg(desc, "%s: unavailable (not requested)\n", __func__);612 status = -EPERM;613 goto err_unlock;614 }615 616 data = kzalloc(sizeof(*data), GFP_KERNEL);617 if (!data) {618 status = -ENOMEM;619 goto err_unlock;620 }621 622 data->desc = desc;623 mutex_init(&data->mutex);624 if (guard.gc->direction_input && guard.gc->direction_output)625 data->direction_can_change = direction_may_change;626 else627 data->direction_can_change = false;628 629 offset = gpio_chip_hwgpio(desc);630 if (guard.gc->names && guard.gc->names[offset])631 ioname = guard.gc->names[offset];632 633 dev = device_create_with_groups(&gpio_class, &gdev->dev,634 MKDEV(0, 0), data, gpio_groups,635 ioname ? ioname : "gpio%u",636 desc_to_gpio(desc));637 if (IS_ERR(dev)) {638 status = PTR_ERR(dev);639 goto err_free_data;640 }641 642 mutex_unlock(&sysfs_lock);643 return 0;644 645err_free_data:646 kfree(data);647err_unlock:648 mutex_unlock(&sysfs_lock);649 clear_bit(FLAG_EXPORT, &desc->flags);650 gpiod_dbg(desc, "%s: status %d\n", __func__, status);651 return status;652}653EXPORT_SYMBOL_GPL(gpiod_export);654 655static int match_export(struct device *dev, const void *desc)656{657 struct gpiod_data *data = dev_get_drvdata(dev);658 659 return data->desc == desc;660}661 662/**663 * gpiod_export_link - create a sysfs link to an exported GPIO node664 * @dev: device under which to create symlink665 * @name: name of the symlink666 * @desc: GPIO to create symlink to, already exported667 *668 * Set up a symlink from /sys/.../dev/name to /sys/class/gpio/gpioN669 * node. Caller is responsible for unlinking.670 *671 * Returns:672 * 0 on success, or negative errno on failure.673 */674int gpiod_export_link(struct device *dev, const char *name,675 struct gpio_desc *desc)676{677 struct device *cdev;678 int ret;679 680 if (!desc) {681 pr_warn("%s: invalid GPIO\n", __func__);682 return -EINVAL;683 }684 685 cdev = class_find_device(&gpio_class, NULL, desc, match_export);686 if (!cdev)687 return -ENODEV;688 689 ret = sysfs_create_link(&dev->kobj, &cdev->kobj, name);690 put_device(cdev);691 692 return ret;693}694EXPORT_SYMBOL_GPL(gpiod_export_link);695 696/**697 * gpiod_unexport - reverse effect of gpiod_export()698 * @desc: GPIO to make unavailable699 *700 * This is implicit on gpiod_free().701 */702void gpiod_unexport(struct gpio_desc *desc)703{704 struct gpiod_data *data;705 struct device *dev;706 707 if (!desc) {708 pr_warn("%s: invalid GPIO\n", __func__);709 return;710 }711 712 mutex_lock(&sysfs_lock);713 714 if (!test_bit(FLAG_EXPORT, &desc->flags))715 goto err_unlock;716 717 dev = class_find_device(&gpio_class, NULL, desc, match_export);718 if (!dev)719 goto err_unlock;720 721 data = dev_get_drvdata(dev);722 723 clear_bit(FLAG_EXPORT, &desc->flags);724 725 device_unregister(dev);726 727 /*728 * Release irq after deregistration to prevent race with edge_store.729 */730 if (data->irq_flags)731 gpio_sysfs_free_irq(dev);732 733 mutex_unlock(&sysfs_lock);734 735 put_device(dev);736 kfree(data);737 738 return;739 740err_unlock:741 mutex_unlock(&sysfs_lock);742}743EXPORT_SYMBOL_GPL(gpiod_unexport);744 745int gpiochip_sysfs_register(struct gpio_device *gdev)746{747 struct gpio_chip *chip;748 struct device *parent;749 struct device *dev;750 751 /*752 * Many systems add gpio chips for SOC support very early,753 * before driver model support is available. In those cases we754 * register later, in gpiolib_sysfs_init() ... here we just755 * verify that _some_ field of gpio_class got initialized.756 */757 if (!class_is_registered(&gpio_class))758 return 0;759 760 guard(srcu)(&gdev->srcu);761 762 chip = srcu_dereference(gdev->chip, &gdev->srcu);763 if (!chip)764 return -ENODEV;765 766 /*767 * For sysfs backward compatibility we need to preserve this768 * preferred parenting to the gpio_chip parent field, if set.769 */770 if (chip->parent)771 parent = chip->parent;772 else773 parent = &gdev->dev;774 775 /* use chip->base for the ID; it's already known to be unique */776 dev = device_create_with_groups(&gpio_class, parent, MKDEV(0, 0), gdev,777 gpiochip_groups, GPIOCHIP_NAME "%d",778 chip->base);779 if (IS_ERR(dev))780 return PTR_ERR(dev);781 782 mutex_lock(&sysfs_lock);783 gdev->mockdev = dev;784 mutex_unlock(&sysfs_lock);785 786 return 0;787}788 789void gpiochip_sysfs_unregister(struct gpio_device *gdev)790{791 struct gpio_desc *desc;792 struct gpio_chip *chip;793 794 scoped_guard(mutex, &sysfs_lock) {795 if (!gdev->mockdev)796 return;797 798 device_unregister(gdev->mockdev);799 800 /* prevent further gpiod exports */801 gdev->mockdev = NULL;802 }803 804 guard(srcu)(&gdev->srcu);805 806 chip = srcu_dereference(gdev->chip, &gdev->srcu);807 if (!chip)808 return;809 810 /* unregister gpiod class devices owned by sysfs */811 for_each_gpio_desc_with_flag(chip, desc, FLAG_SYSFS) {812 gpiod_unexport(desc);813 gpiod_free(desc);814 }815}816 817/*818 * We're not really looking for a device - we just want to iterate over the819 * list and call this callback for each GPIO device. This is why this function820 * always returns 0.821 */822static int gpiofind_sysfs_register(struct gpio_chip *gc, const void *data)823{824 struct gpio_device *gdev = gc->gpiodev;825 int ret;826 827 if (gdev->mockdev)828 return 0;829 830 ret = gpiochip_sysfs_register(gdev);831 if (ret)832 chip_err(gc, "failed to register the sysfs entry: %d\n", ret);833 834 return 0;835}836 837static int __init gpiolib_sysfs_init(void)838{839 int status;840 841 status = class_register(&gpio_class);842 if (status < 0)843 return status;844 845 /* Scan and register the gpio_chips which registered very846 * early (e.g. before the class_register above was called).847 *848 * We run before arch_initcall() so chip->dev nodes can have849 * registered, and so arch_initcall() can always gpiod_export().850 */851 (void)gpio_device_find(NULL, gpiofind_sysfs_register);852 853 return 0;854}855postcore_initcall(gpiolib_sysfs_init);856