drivers/gpio/gpiolib-sysfs.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/idr.h>
   3 #include <linux/mutex.h>
   4 #include <linux/device.h>
   5 #include <linux/sysfs.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 #include <linux/ctype.h>
  12
  13 #include "gpiolib.h"
  14 #include "gpiolib-sysfs.h"
  15
  16 #define GPIO_IRQF_TRIGGER_FALLING       BIT(0)
  17 #define GPIO_IRQF_TRIGGER_RISING        BIT(1)
  18 #define GPIO_IRQF_TRIGGER_BOTH          (GPIO_IRQF_TRIGGER_FALLING | \
  19                                          GPIO_IRQF_TRIGGER_RISING)
  20
  21 struct gpiod_data {
  22         struct gpio_desc *desc;
  23
  24         struct mutex mutex;
  25         struct kernfs_node *value_kn;
  26         int irq;
  27         unsigned char irq_flags;
  28
  29         bool direction_can_change;
  30 };
  31
  32 /*
  33  * Lock to serialise gpiod export and unexport, and prevent re-export of
  34  * gpiod whose chip is being unregistered.
  35  */
  36 static DEFINE_MUTEX(sysfs_lock);
  37
  38 /*
  39  * /sys/class/gpio/gpioN... only for GPIOs that are exported
  40  *   /direction
  41  *      * MAY BE OMITTED if kernel won't allow direction changes
  42  *      * is read/write as "in" or "out"
  43  *      * may also be written as "high" or "low", initializing
  44  *        output value as specified ("out" implies "low")
  45  *   /value
  46  *      * always readable, subject to hardware behavior
  47  *      * may be writable, as zero/nonzero
  48  *   /edge
  49  *      * configures behavior of poll(2) on /value
  50  *      * available only if pin can generate IRQs on input
  51  *      * is read/write as "none", "falling", "rising", or "both"
  52  *   /active_low
  53  *      * configures polarity of /value
  54  *      * is read/write as zero/nonzero
  55  *      * also affects existing and subsequent "falling" and "rising"
  56  *        /edge configuration
  57  */
  58
  59 static ssize_t direction_show(struct device *dev,
  60                 struct device_attribute *attr, char *buf)
  61 {
  62         struct gpiod_data *data = dev_get_drvdata(dev);
  63         struct gpio_desc *desc = data->desc;
  64         ssize_t                 status;
  65
  66         mutex_lock(&data->mutex);
  67
  68         gpiod_get_direction(desc);
  69         status = sprintf(buf, "%s\n",
  70                         test_bit(FLAG_IS_OUT, &desc->flags)
  71                                 ? "out" : "in");
  72
  73         mutex_unlock(&data->mutex);
  74
  75         return status;
  76 }
  77
  78 static ssize_t direction_store(struct device *dev,
  79                 struct device_attribute *attr, const char *buf, size_t size)
  80 {
  81         struct gpiod_data *data = dev_get_drvdata(dev);
  82         struct gpio_desc *desc = data->desc;
  83         ssize_t                 status;
  84
  85         mutex_lock(&data->mutex);
  86
  87         if (sysfs_streq(buf, "high"))
  88                 status = gpiod_direction_output_raw(desc, 1);
  89         else if (sysfs_streq(buf, "out") || sysfs_streq(buf, "low"))
  90                 status = gpiod_direction_output_raw(desc, 0);
  91         else if (sysfs_streq(buf, "in"))
  92                 status = gpiod_direction_input(desc);
  93         else
  94                 status = -EINVAL;
  95
  96         mutex_unlock(&data->mutex);
  97
  98         return status ? : size;
  99 }
 100 static DEVICE_ATTR_RW(direction);
 101
 102 static ssize_t value_show(struct device *dev,
 103                 struct device_attribute *attr, char *buf)
 104 {
 105         struct gpiod_data *data = dev_get_drvdata(dev);
 106         struct gpio_desc *desc = data->desc;
 107         ssize_t                 status;
 108
 109         mutex_lock(&data->mutex);
 110
 111         status = gpiod_get_value_cansleep(desc);
 112         if (status < 0)
 113                 goto err;
 114
 115         buf[0] = '0' + status;
 116         buf[1] = '\n';
 117         status = 2;
 118 err:
 119         mutex_unlock(&data->mutex);
 120
 121         return status;
 122 }
 123
 124 static ssize_t value_store(struct device *dev,
 125                 struct device_attribute *attr, const char *buf, size_t size)
 126 {
 127         struct gpiod_data *data = dev_get_drvdata(dev);
 128         struct gpio_desc *desc = data->desc;
 129         ssize_t status = 0;
 130
 131         mutex_lock(&data->mutex);
 132
 133         if (!test_bit(FLAG_IS_OUT, &desc->flags)) {
 134                 status = -EPERM;
 135         } else {
 136                 long            value;
 137
 138                 if (size <= 2 && isdigit(buf[0]) &&
 139                     (size == 1 || buf[1] == '\n'))
 140                         value = buf[0] - '0';
 141                 else
 142                         status = kstrtol(buf, 0, &value);
 143                 if (status == 0) {
 144                         gpiod_set_value_cansleep(desc, value);
 145                         status = size;
 146                 }
 147         }
 148
 149         mutex_unlock(&data->mutex);
 150
 151         return status;
 152 }
 153 static DEVICE_ATTR_PREALLOC(value, S_IWUSR | S_IRUGO, value_show, value_store);
 154
 155 static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
 156 {
 157         struct gpiod_data *data = priv;
 158
 159         sysfs_notify_dirent(data->value_kn);
 160
 161         return IRQ_HANDLED;
 162 }
 163
 164 /* Caller holds gpiod-data mutex. */
 165 static int gpio_sysfs_request_irq(struct device *dev, unsigned char flags)
 166 {
 167         struct gpiod_data       *data = dev_get_drvdata(dev);
 168         struct gpio_desc        *desc = data->desc;
 169         unsigned long           irq_flags;
 170         int                     ret;
 171
 172         data->irq = gpiod_to_irq(desc);
 173         if (data->irq < 0)
 174                 return -EIO;
 175
 176         data->value_kn = sysfs_get_dirent(dev->kobj.sd, "value");
 177         if (!data->value_kn)
 178                 return -ENODEV;
 179
 180         irq_flags = IRQF_SHARED;
 181         if (flags & GPIO_IRQF_TRIGGER_FALLING)
 182                 irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
 183                         IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING;
 184         if (flags & GPIO_IRQF_TRIGGER_RISING)
 185                 irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
 186                         IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
 187
 188         /*
 189          * FIXME: This should be done in the irq_request_resources callback
 190          *        when the irq is requested, but a few drivers currently fail
 191          *        to do so.
 192          *
 193          *        Remove this redundant call (along with the corresponding
 194          *        unlock) when those drivers have been fixed.
 195          */
 196         ret = gpiochip_lock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc));
 197         if (ret < 0)
 198                 goto err_put_kn;
 199
 200         ret = request_any_context_irq(data->irq, gpio_sysfs_irq, irq_flags,
 201                                 "gpiolib", data);
 202         if (ret < 0)
 203                 goto err_unlock;
 204
 205         data->irq_flags = flags;
 206
 207         return 0;
 208
 209 err_unlock:
 210         gpiochip_unlock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc));
 211 err_put_kn:
 212         sysfs_put(data->value_kn);
 213
 214         return ret;
 215 }
 216
 217 /*
 218  * Caller holds gpiod-data mutex (unless called after class-device
 219  * deregistration).
 220  */
 221 static void gpio_sysfs_free_irq(struct device *dev)
 222 {
 223         struct gpiod_data *data = dev_get_drvdata(dev);
 224         struct gpio_desc *desc = data->desc;
 225
 226         data->irq_flags = 0;
 227         free_irq(data->irq, data);
 228         gpiochip_unlock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc));
 229         sysfs_put(data->value_kn);
 230 }
 231
 232 static const struct {
 233         const char *name;
 234         unsigned char flags;
 235 } trigger_types[] = {
 236         { "none",    0 },
 237         { "falling", GPIO_IRQF_TRIGGER_FALLING },
 238         { "rising",  GPIO_IRQF_TRIGGER_RISING },
 239         { "both",    GPIO_IRQF_TRIGGER_BOTH },
 240 };
 241
 242 static ssize_t edge_show(struct device *dev,
 243                 struct device_attribute *attr, char *buf)
 244 {
 245         struct gpiod_data *data = dev_get_drvdata(dev);
 246         ssize_t status = 0;
 247         int i;
 248
 249         mutex_lock(&data->mutex);
 250
 251         for (i = 0; i < ARRAY_SIZE(trigger_types); i++) {
 252                 if (data->irq_flags == trigger_types[i].flags) {
 253                         status = sprintf(buf, "%s\n", trigger_types[i].name);
 254                         break;
 255                 }
 256         }
 257
 258         mutex_unlock(&data->mutex);
 259
 260         return status;
 261 }
 262
 263 static ssize_t edge_store(struct device *dev,
 264                 struct device_attribute *attr, const char *buf, size_t size)
 265 {
 266         struct gpiod_data *data = dev_get_drvdata(dev);
 267         unsigned char flags;
 268         ssize_t status = size;
 269         int i;
 270
 271         for (i = 0; i < ARRAY_SIZE(trigger_types); i++) {
 272                 if (sysfs_streq(trigger_types[i].name, buf))
 273                         break;
 274         }
 275
 276         if (i == ARRAY_SIZE(trigger_types))
 277                 return -EINVAL;
 278
 279         flags = trigger_types[i].flags;
 280
 281         mutex_lock(&data->mutex);
 282
 283         if (flags == data->irq_flags) {
 284                 status = size;
 285                 goto out_unlock;
 286         }
 287
 288         if (data->irq_flags)
 289                 gpio_sysfs_free_irq(dev);
 290
 291         if (flags) {
 292                 status = gpio_sysfs_request_irq(dev, flags);
 293                 if (!status)
 294                         status = size;
 295         }
 296
 297 out_unlock:
 298         mutex_unlock(&data->mutex);
 299
 300         return status;
 301 }
 302 static DEVICE_ATTR_RW(edge);
 303
 304 /* Caller holds gpiod-data mutex. */
 305 static int gpio_sysfs_set_active_low(struct device *dev, int value)
 306 {
 307         struct gpiod_data       *data = dev_get_drvdata(dev);
 308         struct gpio_desc        *desc = data->desc;
 309         int                     status = 0;
 310         unsigned int            flags = data->irq_flags;
 311
 312         if (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) == !!value)
 313                 return 0;
 314
 315         if (value)
 316                 set_bit(FLAG_ACTIVE_LOW, &desc->flags);
 317         else
 318                 clear_bit(FLAG_ACTIVE_LOW, &desc->flags);
 319
 320         /* reconfigure poll(2) support if enabled on one edge only */
 321         if (flags == GPIO_IRQF_TRIGGER_FALLING ||
 322                                         flags == GPIO_IRQF_TRIGGER_RISING) {
 323                 gpio_sysfs_free_irq(dev);
 324                 status = gpio_sysfs_request_irq(dev, flags);
 325         }
 326
 327         return status;
 328 }
 329
 330 static ssize_t active_low_show(struct device *dev,
 331                 struct device_attribute *attr, char *buf)
 332 {
 333         struct gpiod_data *data = dev_get_drvdata(dev);
 334         struct gpio_desc *desc = data->desc;
 335         ssize_t                 status;
 336
 337         mutex_lock(&data->mutex);
 338
 339         status = sprintf(buf, "%d\n",
 340                                 !!test_bit(FLAG_ACTIVE_LOW, &desc->flags));
 341
 342         mutex_unlock(&data->mutex);
 343
 344         return status;
 345 }
 346
 347 static ssize_t active_low_store(struct device *dev,
 348                 struct device_attribute *attr, const char *buf, size_t size)
 349 {
 350         struct gpiod_data       *data = dev_get_drvdata(dev);
 351         ssize_t                 status;
 352         long                    value;
 353
 354         mutex_lock(&data->mutex);
 355
 356         status = kstrtol(buf, 0, &value);
 357         if (status == 0)
 358                 status = gpio_sysfs_set_active_low(dev, value);
 359
 360         mutex_unlock(&data->mutex);
 361
 362         return status ? : size;
 363 }
 364 static DEVICE_ATTR_RW(active_low);
 365
 366 static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr,
 367                                int n)
 368 {
 369         struct device *dev = kobj_to_dev(kobj);
 370         struct gpiod_data *data = dev_get_drvdata(dev);
 371         struct gpio_desc *desc = data->desc;
 372         umode_t mode = attr->mode;
 373         bool show_direction = data->direction_can_change;
 374
 375         if (attr == &dev_attr_direction.attr) {
 376                 if (!show_direction)
 377                         mode = 0;
 378         } else if (attr == &dev_attr_edge.attr) {
 379                 if (gpiod_to_irq(desc) < 0)
 380                         mode = 0;
 381                 if (!show_direction && test_bit(FLAG_IS_OUT, &desc->flags))
 382                         mode = 0;
 383         }
 384
 385         return mode;
 386 }
 387
 388 static struct attribute *gpio_attrs[] = {
 389         &dev_attr_direction.attr,
 390         &dev_attr_edge.attr,
 391         &dev_attr_value.attr,
 392         &dev_attr_active_low.attr,
 393         NULL,
 394 };
 395
 396 static const struct attribute_group gpio_group = {
 397         .attrs = gpio_attrs,
 398         .is_visible = gpio_is_visible,
 399 };
 400
 401 static const struct attribute_group *gpio_groups[] = {
 402         &gpio_group,
 403         NULL
 404 };
 405
 406 /*
 407  * /sys/class/gpio/gpiochipN/
 408  *   /base ... matching gpio_chip.base (N)
 409  *   /label ... matching gpio_chip.label
 410  *   /ngpio ... matching gpio_chip.ngpio
 411  */
 412
 413 static ssize_t base_show(struct device *dev,
 414                                struct device_attribute *attr, char *buf)
 415 {
 416         const struct gpio_chip  *chip = dev_get_drvdata(dev);
 417
 418         return sprintf(buf, "%d\n", chip->base);
 419 }
 420 static DEVICE_ATTR_RO(base);
 421
 422 static ssize_t label_show(struct device *dev,
 423                                struct device_attribute *attr, char *buf)
 424 {
 425         const struct gpio_chip  *chip = dev_get_drvdata(dev);
 426
 427         return sprintf(buf, "%s\n", chip->label ? : "");
 428 }
 429 static DEVICE_ATTR_RO(label);
 430
 431 static ssize_t ngpio_show(struct device *dev,
 432                                struct device_attribute *attr, char *buf)
 433 {
 434         const struct gpio_chip  *chip = dev_get_drvdata(dev);
 435
 436         return sprintf(buf, "%u\n", chip->ngpio);
 437 }
 438 static DEVICE_ATTR_RO(ngpio);
 439
 440 static struct attribute *gpiochip_attrs[] = {
 441         &dev_attr_base.attr,
 442         &dev_attr_label.attr,
 443         &dev_attr_ngpio.attr,
 444         NULL,
 445 };
 446 ATTRIBUTE_GROUPS(gpiochip);
 447
 448 /*
 449  * /sys/class/gpio/export ... write-only
 450  *      integer N ... number of GPIO to export (full access)
 451  * /sys/class/gpio/unexport ... write-only
 452  *      integer N ... number of GPIO to unexport
 453  */
 454 static ssize_t export_store(struct class *class,
 455                                 struct class_attribute *attr,
 456                                 const char *buf, size_t len)
 457 {
 458         long                    gpio;
 459         struct gpio_desc        *desc;
 460         int                     status;
 461
 462         status = kstrtol(buf, 0, &gpio);
 463         if (status < 0)
 464                 goto done;
 465
 466         desc = gpio_to_desc(gpio);
 467         /* reject invalid GPIOs */
 468         if (!desc) {
 469                 pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
 470                 return -EINVAL;
 471         }
 472
 473         /* No extra locking here; FLAG_SYSFS just signifies that the
 474          * request and export were done by on behalf of userspace, so
 475          * they may be undone on its behalf too.
 476          */
 477
 478         status = gpiod_request(desc, "sysfs");
 479         if (status) {
 480                 if (status == -EPROBE_DEFER)
 481                         status = -ENODEV;
 482                 goto done;
 483         }
 484
 485         status = gpiod_set_transitory(desc, false);
 486         if (!status) {
 487                 status = gpiod_export(desc, true);
 488                 if (status < 0)
 489                         gpiod_free(desc);
 490                 else
 491                         set_bit(FLAG_SYSFS, &desc->flags);
 492         }
 493
 494 done:
 495         if (status)
 496                 pr_debug("%s: status %d\n", __func__, status);
 497         return status ? : len;
 498 }
 499 static CLASS_ATTR_WO(export);
 500
 501 static ssize_t unexport_store(struct class *class,
 502                                 struct class_attribute *attr,
 503                                 const char *buf, size_t len)
 504 {
 505         long                    gpio;
 506         struct gpio_desc        *desc;
 507         int                     status;
 508
 509         status = kstrtol(buf, 0, &gpio);
 510         if (status < 0)
 511                 goto done;
 512
 513         desc = gpio_to_desc(gpio);
 514         /* reject bogus commands (gpio_unexport ignores them) */
 515         if (!desc) {
 516                 pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
 517                 return -EINVAL;
 518         }
 519
 520         status = -EINVAL;
 521
 522         /* No extra locking here; FLAG_SYSFS just signifies that the
 523          * request and export were done by on behalf of userspace, so
 524          * they may be undone on its behalf too.
 525          */
 526         if (test_and_clear_bit(FLAG_SYSFS, &desc->flags)) {
 527                 status = 0;
 528                 gpiod_free(desc);
 529         }
 530 done:
 531         if (status)
 532                 pr_debug("%s: status %d\n", __func__, status);
 533         return status ? : len;
 534 }
 535 static CLASS_ATTR_WO(unexport);
 536
 537 static struct attribute *gpio_class_attrs[] = {
 538         &class_attr_export.attr,
 539         &class_attr_unexport.attr,
 540         NULL,
 541 };
 542 ATTRIBUTE_GROUPS(gpio_class);
 543
 544 static struct class gpio_class = {
 545         .name =         "gpio",
 546         .owner =        THIS_MODULE,
 547
 548         .class_groups = gpio_class_groups,
 549 };
 550
 551
 552 /**
 553  * gpiod_export - export a GPIO through sysfs
 554  * @desc: GPIO to make available, already requested
 555  * @direction_may_change: true if userspace may change GPIO direction
 556  * Context: arch_initcall or later
 557  *
 558  * When drivers want to make a GPIO accessible to userspace after they
 559  * have requested it -- perhaps while debugging, or as part of their
 560  * public interface -- they may use this routine.  If the GPIO can
 561  * change direction (some can't) and the caller allows it, userspace
 562  * will see "direction" sysfs attribute which may be used to change
 563  * the gpio's direction.  A "value" attribute will always be provided.
 564  *
 565  * Returns zero on success, else an error.
 566  */
 567 int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 568 {
 569         struct gpio_chip        *chip;
 570         struct gpio_device      *gdev;
 571         struct gpiod_data       *data;
 572         unsigned long           flags;
 573         int                     status;
 574         const char              *ioname = NULL;
 575         struct device           *dev;
 576         int                     offset;
 577
 578         /* can't export until sysfs is available ... */
 579         if (!gpio_class.p) {
 580                 pr_debug("%s: called too early!\n", __func__);
 581                 return -ENOENT;
 582         }
 583
 584         if (!desc) {
 585                 pr_debug("%s: invalid gpio descriptor\n", __func__);
 586                 return -EINVAL;
 587         }
 588
 589         gdev = desc->gdev;
 590         chip = gdev->chip;
 591
 592         mutex_lock(&sysfs_lock);
 593
 594         /* check if chip is being removed */
 595         if (!chip || !gdev->mockdev) {
 596                 status = -ENODEV;
 597                 goto err_unlock;
 598         }
 599
 600         spin_lock_irqsave(&gpio_lock, flags);
 601         if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
 602              test_bit(FLAG_EXPORT, &desc->flags)) {
 603                 spin_unlock_irqrestore(&gpio_lock, flags);
 604                 gpiod_dbg(desc, "%s: unavailable (requested=%d, exported=%d)\n",
 605                                 __func__,
 606                                 test_bit(FLAG_REQUESTED, &desc->flags),
 607                                 test_bit(FLAG_EXPORT, &desc->flags));
 608                 status = -EPERM;
 609                 goto err_unlock;
 610         }
 611         spin_unlock_irqrestore(&gpio_lock, flags);
 612
 613         data = kzalloc(sizeof(*data), GFP_KERNEL);
 614         if (!data) {
 615                 status = -ENOMEM;
 616                 goto err_unlock;
 617         }
 618
 619         data->desc = desc;
 620         mutex_init(&data->mutex);
 621         if (chip->direction_input && chip->direction_output)
 622                 data->direction_can_change = direction_may_change;
 623         else
 624                 data->direction_can_change = false;
 625
 626         offset = gpio_chip_hwgpio(desc);
 627         if (chip->names && chip->names[offset])
 628                 ioname = chip->names[offset];
 629
 630         dev = device_create_with_groups(&gpio_class, &gdev->dev,
 631                                         MKDEV(0, 0), data, gpio_groups,
 632                                         ioname ? ioname : "gpio%u",
 633                                         desc_to_gpio(desc));
 634         if (IS_ERR(dev)) {
 635                 status = PTR_ERR(dev);
 636                 goto err_free_data;
 637         }
 638
 639         set_bit(FLAG_EXPORT, &desc->flags);
 640         mutex_unlock(&sysfs_lock);
 641         return 0;
 642
 643 err_free_data:
 644         kfree(data);
 645 err_unlock:
 646         mutex_unlock(&sysfs_lock);
 647         gpiod_dbg(desc, "%s: status %d\n", __func__, status);
 648         return status;
 649 }
 650 EXPORT_SYMBOL_GPL(gpiod_export);
 651
 652 static int match_export(struct device *dev, const void *desc)
 653 {
 654         struct gpiod_data *data = dev_get_drvdata(dev);
 655
 656         return data->desc == desc;
 657 }
 658
 659 /**
 660  * gpiod_export_link - create a sysfs link to an exported GPIO node
 661  * @dev: device under which to create symlink
 662  * @name: name of the symlink
 663  * @desc: GPIO to create symlink to, already exported
 664  *
 665  * Set up a symlink from /sys/.../dev/name to /sys/class/gpio/gpioN
 666  * node. Caller is responsible for unlinking.
 667  *
 668  * Returns zero on success, else an error.
 669  */
 670 int gpiod_export_link(struct device *dev, const char *name,
 671                       struct gpio_desc *desc)
 672 {
 673         struct device *cdev;
 674         int ret;
 675
 676         if (!desc) {
 677                 pr_warn("%s: invalid GPIO\n", __func__);
 678                 return -EINVAL;
 679         }
 680
 681         cdev = class_find_device(&gpio_class, NULL, desc, match_export);
 682         if (!cdev)
 683                 return -ENODEV;
 684
 685         ret = sysfs_create_link(&dev->kobj, &cdev->kobj, name);
 686         put_device(cdev);
 687
 688         return ret;
 689 }
 690 EXPORT_SYMBOL_GPL(gpiod_export_link);
 691
 692 /**
 693  * gpiod_unexport - reverse effect of gpiod_export()
 694  * @desc: GPIO to make unavailable
 695  *
 696  * This is implicit on gpiod_free().
 697  */
 698 void gpiod_unexport(struct gpio_desc *desc)
 699 {
 700         struct gpiod_data *data;
 701         struct device *dev;
 702
 703         if (!desc) {
 704                 pr_warn("%s: invalid GPIO\n", __func__);
 705                 return;
 706         }
 707
 708         mutex_lock(&sysfs_lock);
 709
 710         if (!test_bit(FLAG_EXPORT, &desc->flags))
 711                 goto err_unlock;
 712
 713         dev = class_find_device(&gpio_class, NULL, desc, match_export);
 714         if (!dev)
 715                 goto err_unlock;
 716
 717         data = dev_get_drvdata(dev);
 718
 719         clear_bit(FLAG_EXPORT, &desc->flags);
 720
 721         device_unregister(dev);
 722
 723         /*
 724          * Release irq after deregistration to prevent race with edge_store.
 725          */
 726         if (data->irq_flags)
 727                 gpio_sysfs_free_irq(dev);
 728
 729         mutex_unlock(&sysfs_lock);
 730
 731         put_device(dev);
 732         kfree(data);
 733
 734         return;
 735
 736 err_unlock:
 737         mutex_unlock(&sysfs_lock);
 738 }
 739 EXPORT_SYMBOL_GPL(gpiod_unexport);
 740
 741 int gpiochip_sysfs_register(struct gpio_device *gdev)
 742 {
 743         struct device   *dev;
 744         struct device   *parent;
 745         struct gpio_chip *chip = gdev->chip;
 746
 747         /*
 748          * Many systems add gpio chips for SOC support very early,
 749          * before driver model support is available.  In those cases we
 750          * register later, in gpiolib_sysfs_init() ... here we just
 751          * verify that _some_ field of gpio_class got initialized.
 752          */
 753         if (!gpio_class.p)
 754                 return 0;
 755
 756         /*
 757          * For sysfs backward compatibility we need to preserve this
 758          * preferred parenting to the gpio_chip parent field, if set.
 759          */
 760         if (chip->parent)
 761                 parent = chip->parent;
 762         else
 763                 parent = &gdev->dev;
 764
 765         /* use chip->base for the ID; it's already known to be unique */
 766         dev = device_create_with_groups(&gpio_class, parent, MKDEV(0, 0), chip,
 767                                         gpiochip_groups, GPIOCHIP_NAME "%d",
 768                                         chip->base);
 769         if (IS_ERR(dev))
 770                 return PTR_ERR(dev);
 771
 772         mutex_lock(&sysfs_lock);
 773         gdev->mockdev = dev;
 774         mutex_unlock(&sysfs_lock);
 775
 776         return 0;
 777 }
 778
 779 void gpiochip_sysfs_unregister(struct gpio_device *gdev)
 780 {
 781         struct gpio_desc *desc;
 782         struct gpio_chip *chip = gdev->chip;
 783         unsigned int i;
 784
 785         if (!gdev->mockdev)
 786                 return;
 787
 788         device_unregister(gdev->mockdev);
 789
 790         /* prevent further gpiod exports */
 791         mutex_lock(&sysfs_lock);
 792         gdev->mockdev = NULL;
 793         mutex_unlock(&sysfs_lock);
 794
 795         /* unregister gpiod class devices owned by sysfs */
 796         for (i = 0; i < chip->ngpio; i++) {
 797                 desc = &gdev->descs[i];
 798                 if (test_and_clear_bit(FLAG_SYSFS, &desc->flags))
 799                         gpiod_free(desc);
 800         }
 801 }
 802
 803 static int __init gpiolib_sysfs_init(void)
 804 {
 805         int             status;
 806         unsigned long   flags;
 807         struct gpio_device *gdev;
 808
 809         status = class_register(&gpio_class);
 810         if (status < 0)
 811                 return status;
 812
 813         /* Scan and register the gpio_chips which registered very
 814          * early (e.g. before the class_register above was called).
 815          *
 816          * We run before arch_initcall() so chip->dev nodes can have
 817          * registered, and so arch_initcall() can always gpio_export().
 818          */
 819         spin_lock_irqsave(&gpio_lock, flags);
 820         list_for_each_entry(gdev, &gpio_devices, list) {
 821                 if (gdev->mockdev)
 822                         continue;
 823
 824                 /*
 825                  * TODO we yield gpio_lock here because
 826                  * gpiochip_sysfs_register() acquires a mutex. This is unsafe
 827                  * and needs to be fixed.
 828                  *
 829                  * Also it would be nice to use gpiochip_find() here so we
 830                  * can keep gpio_chips local to gpiolib.c, but the yield of
 831                  * gpio_lock prevents us from doing this.
 832                  */
 833                 spin_unlock_irqrestore(&gpio_lock, flags);
 834                 status = gpiochip_sysfs_register(gdev);
 835                 spin_lock_irqsave(&gpio_lock, flags);
 836         }
 837         spin_unlock_irqrestore(&gpio_lock, flags);
 838
 839         return status;
 840 }
 841 postcore_initcall(gpiolib_sysfs_init);