drivers/gpio/gpiolib-sysfs.c

   1 #include <linux/idr.h>
   2 #include <linux/mutex.h>
   3 #include <linux/device.h>
   4 #include <linux/sysfs.h>
   5 #include <linux/gpio/consumer.h>
   6 #include <linux/gpio/driver.h>
   7 #include <linux/interrupt.h>
   8 #include <linux/kdev_t.h>
   9 #include <linux/slab.h>
  10
  11 #include "gpiolib.h"
  12
  13 #define GPIO_IRQF_TRIGGER_FALLING       BIT(0)
  14 #define GPIO_IRQF_TRIGGER_RISING        BIT(1)
  15 #define GPIO_IRQF_TRIGGER_BOTH          (GPIO_IRQF_TRIGGER_FALLING | \
  16                                          GPIO_IRQF_TRIGGER_RISING)
  17
  18 struct gpiod_data {
  19         struct gpio_desc *desc;
  20
  21         struct mutex mutex;
  22         struct kernfs_node *value_kn;
  23         int irq;
  24         unsigned char irq_flags;
  25
  26         bool direction_can_change;
  27 };
  28
  29 /*
  30  * Lock to serialise gpiod export and unexport, and prevent re-export of
  31  * gpiod whose chip is being unregistered.
  32  */
  33 static DEFINE_MUTEX(sysfs_lock);
  34
  35 /*
  36  * /sys/class/gpio/gpioN... only for GPIOs that are exported
  37  *   /direction
  38  *      * MAY BE OMITTED if kernel won't allow direction changes
  39  *      * is read/write as "in" or "out"
  40  *      * may also be written as "high" or "low", initializing
  41  *        output value as specified ("out" implies "low")
  42  *   /value
  43  *      * always readable, subject to hardware behavior
  44  *      * may be writable, as zero/nonzero
  45  *   /edge
  46  *      * configures behavior of poll(2) on /value
  47  *      * available only if pin can generate IRQs on input
  48  *      * is read/write as "none", "falling", "rising", or "both"
  49  *   /active_low
  50  *      * configures polarity of /value
  51  *      * is read/write as zero/nonzero
  52  *      * also affects existing and subsequent "falling" and "rising"
  53  *        /edge configuration
  54  */
  55
  56 static ssize_t direction_show(struct device *dev,
  57                 struct device_attribute *attr, char *buf)
  58 {
  59         struct gpiod_data *data = dev_get_drvdata(dev);
  60         struct gpio_desc *desc = data->desc;
  61         ssize_t                 status;
  62
  63         mutex_lock(&data->mutex);
  64
  65         gpiod_get_direction(desc);
  66         status = sprintf(buf, "%s\n",
  67                         test_bit(FLAG_IS_OUT, &desc->flags)
  68                                 ? "out" : "in");
  69
  70         mutex_unlock(&data->mutex);
  71
  72         return status;
  73 }
  74
  75 static ssize_t direction_store(struct device *dev,
  76                 struct device_attribute *attr, const char *buf, size_t size)
  77 {
  78         struct gpiod_data *data = dev_get_drvdata(dev);
  79         struct gpio_desc *desc = data->desc;
  80         ssize_t                 status;
  81
  82         mutex_lock(&data->mutex);
  83
  84         if (sysfs_streq(buf, "high"))
  85                 status = gpiod_direction_output_raw(desc, 1);
  86         else if (sysfs_streq(buf, "out") || sysfs_streq(buf, "low"))
  87                 status = gpiod_direction_output_raw(desc, 0);
  88         else if (sysfs_streq(buf, "in"))
  89                 status = gpiod_direction_input(desc);
  90         else
  91                 status = -EINVAL;
  92
  93         mutex_unlock(&data->mutex);
  94
  95         return status ? : size;
  96 }
  97 static DEVICE_ATTR_RW(direction);
  98
  99 static ssize_t value_show(struct device *dev,
 100                 struct device_attribute *attr, char *buf)
 101 {
 102         struct gpiod_data *data = dev_get_drvdata(dev);
 103         struct gpio_desc *desc = data->desc;
 104         ssize_t                 status;
 105
 106         mutex_lock(&data->mutex);
 107
 108         status = sprintf(buf, "%d\n", gpiod_get_value_cansleep(desc));
 109
 110         mutex_unlock(&data->mutex);
 111
 112         return status;
 113 }
 114
 115 static ssize_t value_store(struct device *dev,
 116                 struct device_attribute *attr, const char *buf, size_t size)
 117 {
 118         struct gpiod_data *data = dev_get_drvdata(dev);
 119         struct gpio_desc *desc = data->desc;
 120         ssize_t                 status;
 121
 122         mutex_lock(&data->mutex);
 123
 124         if (!test_bit(FLAG_IS_OUT, &desc->flags)) {
 125                 status = -EPERM;
 126         } else {
 127                 long            value;
 128
 129                 status = kstrtol(buf, 0, &value);
 130                 if (status == 0) {
 131                         gpiod_set_value_cansleep(desc, value);
 132                         status = size;
 133                 }
 134         }
 135
 136         mutex_unlock(&data->mutex);
 137
 138         return status;
 139 }
 140 static DEVICE_ATTR_RW(value);
 141
 142 static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
 143 {
 144         struct gpiod_data *data = priv;
 145
 146         sysfs_notify_dirent(data->value_kn);
 147
 148         return IRQ_HANDLED;
 149 }
 150
 151 /* Caller holds gpiod-data mutex. */
 152 static int gpio_sysfs_request_irq(struct device *dev, unsigned char flags)
 153 {
 154         struct gpiod_data       *data = dev_get_drvdata(dev);
 155         struct gpio_desc        *desc = data->desc;
 156         unsigned long           irq_flags;
 157         int                     ret;
 158
 159         data->irq = gpiod_to_irq(desc);
 160         if (data->irq < 0)
 161                 return -EIO;
 162
 163         data->value_kn = sysfs_get_dirent(dev->kobj.sd, "value");
 164         if (!data->value_kn)
 165                 return -ENODEV;
 166
 167         irq_flags = IRQF_SHARED;
 168         if (flags & GPIO_IRQF_TRIGGER_FALLING)
 169                 irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
 170                         IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING;
 171         if (flags & GPIO_IRQF_TRIGGER_RISING)
 172                 irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
 173                         IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
 174
 175         /*
 176          * FIXME: This should be done in the irq_request_resources callback
 177          *        when the irq is requested, but a few drivers currently fail
 178          *        to do so.
 179          *
 180          *        Remove this redundant call (along with the corresponding
 181          *        unlock) when those drivers have been fixed.
 182          */
 183         ret = gpiochip_lock_as_irq(desc->chip, gpio_chip_hwgpio(desc));
 184         if (ret < 0)
 185                 goto err_put_kn;
 186
 187         ret = request_any_context_irq(data->irq, gpio_sysfs_irq, irq_flags,
 188                                 "gpiolib", data);
 189         if (ret < 0)
 190                 goto err_unlock;
 191
 192         data->irq_flags = flags;
 193
 194         return 0;
 195
 196 err_unlock:
 197         gpiochip_unlock_as_irq(desc->chip, gpio_chip_hwgpio(desc));
 198 err_put_kn:
 199         sysfs_put(data->value_kn);
 200
 201         return ret;
 202 }
 203
 204 /*
 205  * Caller holds gpiod-data mutex (unless called after class-device
 206  * deregistration).
 207  */
 208 static void gpio_sysfs_free_irq(struct device *dev)
 209 {
 210         struct gpiod_data *data = dev_get_drvdata(dev);
 211         struct gpio_desc *desc = data->desc;
 212
 213         data->irq_flags = 0;
 214         free_irq(data->irq, data);
 215         gpiochip_unlock_as_irq(desc->chip, gpio_chip_hwgpio(desc));
 216         sysfs_put(data->value_kn);
 217 }
 218
 219 static const struct {
 220         const char *name;
 221         unsigned char flags;
 222 } trigger_types[] = {
 223         { "none",    0 },
 224         { "falling", GPIO_IRQF_TRIGGER_FALLING },
 225         { "rising",  GPIO_IRQF_TRIGGER_RISING },
 226         { "both",    GPIO_IRQF_TRIGGER_BOTH },
 227 };
 228
 229 static ssize_t edge_show(struct device *dev,
 230                 struct device_attribute *attr, char *buf)
 231 {
 232         struct gpiod_data *data = dev_get_drvdata(dev);
 233         ssize_t status = 0;
 234         int i;
 235
 236         mutex_lock(&data->mutex);
 237
 238         for (i = 0; i < ARRAY_SIZE(trigger_types); i++) {
 239                 if (data->irq_flags == trigger_types[i].flags) {
 240                         status = sprintf(buf, "%s\n", trigger_types[i].name);
 241                         break;
 242                 }
 243         }
 244
 245         mutex_unlock(&data->mutex);
 246
 247         return status;
 248 }
 249
 250 static ssize_t edge_store(struct device *dev,
 251                 struct device_attribute *attr, const char *buf, size_t size)
 252 {
 253         struct gpiod_data *data = dev_get_drvdata(dev);
 254         unsigned char flags;
 255         ssize_t status = size;
 256         int i;
 257
 258         for (i = 0; i < ARRAY_SIZE(trigger_types); i++) {
 259                 if (sysfs_streq(trigger_types[i].name, buf))
 260                         break;
 261         }
 262
 263         if (i == ARRAY_SIZE(trigger_types))
 264                 return -EINVAL;
 265
 266         flags = trigger_types[i].flags;
 267
 268         mutex_lock(&data->mutex);
 269
 270         if (flags == data->irq_flags) {
 271                 status = size;
 272                 goto out_unlock;
 273         }
 274
 275         if (data->irq_flags)
 276                 gpio_sysfs_free_irq(dev);
 277
 278         if (flags) {
 279                 status = gpio_sysfs_request_irq(dev, flags);
 280                 if (!status)
 281                         status = size;
 282         }
 283
 284 out_unlock:
 285         mutex_unlock(&data->mutex);
 286
 287         return status;
 288 }
 289 static DEVICE_ATTR_RW(edge);
 290
 291 /* Caller holds gpiod-data mutex. */
 292 static int gpio_sysfs_set_active_low(struct device *dev, int value)
 293 {
 294         struct gpiod_data       *data = dev_get_drvdata(dev);
 295         struct gpio_desc        *desc = data->desc;
 296         int                     status = 0;
 297         unsigned int            flags = data->irq_flags;
 298
 299         if (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) == !!value)
 300                 return 0;
 301
 302         if (value)
 303                 set_bit(FLAG_ACTIVE_LOW, &desc->flags);
 304         else
 305                 clear_bit(FLAG_ACTIVE_LOW, &desc->flags);
 306
 307         /* reconfigure poll(2) support if enabled on one edge only */
 308         if (flags == GPIO_IRQF_TRIGGER_FALLING ||
 309                                         flags == GPIO_IRQF_TRIGGER_RISING) {
 310                 gpio_sysfs_free_irq(dev);
 311                 status = gpio_sysfs_request_irq(dev, flags);
 312         }
 313
 314         return status;
 315 }
 316
 317 static ssize_t active_low_show(struct device *dev,
 318                 struct device_attribute *attr, char *buf)
 319 {
 320         struct gpiod_data *data = dev_get_drvdata(dev);
 321         struct gpio_desc *desc = data->desc;
 322         ssize_t                 status;
 323
 324         mutex_lock(&data->mutex);
 325
 326         status = sprintf(buf, "%d\n",
 327                                 !!test_bit(FLAG_ACTIVE_LOW, &desc->flags));
 328
 329         mutex_unlock(&data->mutex);
 330
 331         return status;
 332 }
 333
 334 static ssize_t active_low_store(struct device *dev,
 335                 struct device_attribute *attr, const char *buf, size_t size)
 336 {
 337         struct gpiod_data       *data = dev_get_drvdata(dev);
 338         ssize_t                 status;
 339         long                    value;
 340
 341         mutex_lock(&data->mutex);
 342
 343         status = kstrtol(buf, 0, &value);
 344         if (status == 0)
 345                 status = gpio_sysfs_set_active_low(dev, value);
 346
 347         mutex_unlock(&data->mutex);
 348
 349         return status ? : size;
 350 }
 351 static DEVICE_ATTR_RW(active_low);
 352
 353 static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr,
 354                                int n)
 355 {
 356         struct device *dev = container_of(kobj, struct device, kobj);
 357         struct gpiod_data *data = dev_get_drvdata(dev);
 358         struct gpio_desc *desc = data->desc;
 359         umode_t mode = attr->mode;
 360         bool show_direction = data->direction_can_change;
 361
 362         if (attr == &dev_attr_direction.attr) {
 363                 if (!show_direction)
 364                         mode = 0;
 365         } else if (attr == &dev_attr_edge.attr) {
 366                 if (gpiod_to_irq(desc) < 0)
 367                         mode = 0;
 368                 if (!show_direction && test_bit(FLAG_IS_OUT, &desc->flags))
 369                         mode = 0;
 370         }
 371
 372         return mode;
 373 }
 374
 375 static struct attribute *gpio_attrs[] = {
 376         &dev_attr_direction.attr,
 377         &dev_attr_edge.attr,
 378         &dev_attr_value.attr,
 379         &dev_attr_active_low.attr,
 380         NULL,
 381 };
 382
 383 static const struct attribute_group gpio_group = {
 384         .attrs = gpio_attrs,
 385         .is_visible = gpio_is_visible,
 386 };
 387
 388 static const struct attribute_group *gpio_groups[] = {
 389         &gpio_group,
 390         NULL
 391 };
 392
 393 /*
 394  * /sys/class/gpio/gpiochipN/
 395  *   /base ... matching gpio_chip.base (N)
 396  *   /label ... matching gpio_chip.label
 397  *   /ngpio ... matching gpio_chip.ngpio
 398  */
 399
 400 static ssize_t base_show(struct device *dev,
 401                                struct device_attribute *attr, char *buf)
 402 {
 403         const struct gpio_chip  *chip = dev_get_drvdata(dev);
 404
 405         return sprintf(buf, "%d\n", chip->base);
 406 }
 407 static DEVICE_ATTR_RO(base);
 408
 409 static ssize_t label_show(struct device *dev,
 410                                struct device_attribute *attr, char *buf)
 411 {
 412         const struct gpio_chip  *chip = dev_get_drvdata(dev);
 413
 414         return sprintf(buf, "%s\n", chip->label ? : "");
 415 }
 416 static DEVICE_ATTR_RO(label);
 417
 418 static ssize_t ngpio_show(struct device *dev,
 419                                struct device_attribute *attr, char *buf)
 420 {
 421         const struct gpio_chip  *chip = dev_get_drvdata(dev);
 422
 423         return sprintf(buf, "%u\n", chip->ngpio);
 424 }
 425 static DEVICE_ATTR_RO(ngpio);
 426
 427 static struct attribute *gpiochip_attrs[] = {
 428         &dev_attr_base.attr,
 429         &dev_attr_label.attr,
 430         &dev_attr_ngpio.attr,
 431         NULL,
 432 };
 433 ATTRIBUTE_GROUPS(gpiochip);
 434
 435 /*
 436  * /sys/class/gpio/export ... write-only
 437  *      integer N ... number of GPIO to export (full access)
 438  * /sys/class/gpio/unexport ... write-only
 439  *      integer N ... number of GPIO to unexport
 440  */
 441 static ssize_t export_store(struct class *class,
 442                                 struct class_attribute *attr,
 443                                 const char *buf, size_t len)
 444 {
 445         long                    gpio;
 446         struct gpio_desc        *desc;
 447         int                     status;
 448
 449         status = kstrtol(buf, 0, &gpio);
 450         if (status < 0)
 451                 goto done;
 452
 453         desc = gpio_to_desc(gpio);
 454         /* reject invalid GPIOs */
 455         if (!desc) {
 456                 pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
 457                 return -EINVAL;
 458         }
 459
 460         /* No extra locking here; FLAG_SYSFS just signifies that the
 461          * request and export were done by on behalf of userspace, so
 462          * they may be undone on its behalf too.
 463          */
 464
 465         status = gpiod_request(desc, "sysfs");
 466         if (status < 0) {
 467                 if (status == -EPROBE_DEFER)
 468                         status = -ENODEV;
 469                 goto done;
 470         }
 471         status = gpiod_export(desc, true);
 472         if (status < 0)
 473                 gpiod_free(desc);
 474         else
 475                 set_bit(FLAG_SYSFS, &desc->flags);
 476
 477 done:
 478         if (status)
 479                 pr_debug("%s: status %d\n", __func__, status);
 480         return status ? : len;
 481 }
 482
 483 static ssize_t unexport_store(struct class *class,
 484                                 struct class_attribute *attr,
 485                                 const char *buf, size_t len)
 486 {
 487         long                    gpio;
 488         struct gpio_desc        *desc;
 489         int                     status;
 490
 491         status = kstrtol(buf, 0, &gpio);
 492         if (status < 0)
 493                 goto done;
 494
 495         desc = gpio_to_desc(gpio);
 496         /* reject bogus commands (gpio_unexport ignores them) */
 497         if (!desc) {
 498                 pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
 499                 return -EINVAL;
 500         }
 501
 502         status = -EINVAL;
 503
 504         /* No extra locking here; FLAG_SYSFS just signifies that the
 505          * request and export were done by on behalf of userspace, so
 506          * they may be undone on its behalf too.
 507          */
 508         if (test_and_clear_bit(FLAG_SYSFS, &desc->flags)) {
 509                 status = 0;
 510                 gpiod_free(desc);
 511         }
 512 done:
 513         if (status)
 514                 pr_debug("%s: status %d\n", __func__, status);
 515         return status ? : len;
 516 }
 517
 518 static struct class_attribute gpio_class_attrs[] = {
 519         __ATTR(export, 0200, NULL, export_store),
 520         __ATTR(unexport, 0200, NULL, unexport_store),
 521         __ATTR_NULL,
 522 };
 523
 524 static struct class gpio_class = {
 525         .name =         "gpio",
 526         .owner =        THIS_MODULE,
 527
 528         .class_attrs =  gpio_class_attrs,
 529 };
 530
 531
 532 /**
 533  * gpiod_export - export a GPIO through sysfs
 534  * @gpio: gpio to make available, already requested
 535  * @direction_may_change: true if userspace may change gpio direction
 536  * Context: arch_initcall or later
 537  *
 538  * When drivers want to make a GPIO accessible to userspace after they
 539  * have requested it -- perhaps while debugging, or as part of their
 540  * public interface -- they may use this routine.  If the GPIO can
 541  * change direction (some can't) and the caller allows it, userspace
 542  * will see "direction" sysfs attribute which may be used to change
 543  * the gpio's direction.  A "value" attribute will always be provided.
 544  *
 545  * Returns zero on success, else an error.
 546  */
 547 int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 548 {
 549         struct gpio_chip        *chip;
 550         struct gpiod_data       *data;
 551         unsigned long           flags;
 552         int                     status;
 553         const char              *ioname = NULL;
 554         struct device           *dev;
 555         int                     offset;
 556
 557         /* can't export until sysfs is available ... */
 558         if (!gpio_class.p) {
 559                 pr_debug("%s: called too early!\n", __func__);
 560                 return -ENOENT;
 561         }
 562
 563         if (!desc) {
 564                 pr_debug("%s: invalid gpio descriptor\n", __func__);
 565                 return -EINVAL;
 566         }
 567
 568         chip = desc->chip;
 569
 570         mutex_lock(&sysfs_lock);
 571
 572         /* check if chip is being removed */
 573         if (!chip || !chip->cdev) {
 574                 status = -ENODEV;
 575                 goto err_unlock;
 576         }
 577
 578         spin_lock_irqsave(&gpio_lock, flags);
 579         if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
 580              test_bit(FLAG_EXPORT, &desc->flags)) {
 581                 spin_unlock_irqrestore(&gpio_lock, flags);
 582                 gpiod_dbg(desc, "%s: unavailable (requested=%d, exported=%d)\n",
 583                                 __func__,
 584                                 test_bit(FLAG_REQUESTED, &desc->flags),
 585                                 test_bit(FLAG_EXPORT, &desc->flags));
 586                 status = -EPERM;
 587                 goto err_unlock;
 588         }
 589         spin_unlock_irqrestore(&gpio_lock, flags);
 590
 591         data = kzalloc(sizeof(*data), GFP_KERNEL);
 592         if (!data) {
 593                 status = -ENOMEM;
 594                 goto err_unlock;
 595         }
 596
 597         data->desc = desc;
 598         mutex_init(&data->mutex);
 599         if (chip->direction_input && chip->direction_output)
 600                 data->direction_can_change = direction_may_change;
 601         else
 602                 data->direction_can_change = false;
 603
 604         offset = gpio_chip_hwgpio(desc);
 605         if (chip->names && chip->names[offset])
 606                 ioname = chip->names[offset];
 607
 608         dev = device_create_with_groups(&gpio_class, chip->dev,
 609                                         MKDEV(0, 0), data, gpio_groups,
 610                                         ioname ? ioname : "gpio%u",
 611                                         desc_to_gpio(desc));
 612         if (IS_ERR(dev)) {
 613                 status = PTR_ERR(dev);
 614                 goto err_free_data;
 615         }
 616
 617         set_bit(FLAG_EXPORT, &desc->flags);
 618         mutex_unlock(&sysfs_lock);
 619         return 0;
 620
 621 err_free_data:
 622         kfree(data);
 623 err_unlock:
 624         mutex_unlock(&sysfs_lock);
 625         gpiod_dbg(desc, "%s: status %d\n", __func__, status);
 626         return status;
 627 }
 628 EXPORT_SYMBOL_GPL(gpiod_export);
 629
 630 static int match_export(struct device *dev, const void *desc)
 631 {
 632         struct gpiod_data *data = dev_get_drvdata(dev);
 633
 634         return data->desc == desc;
 635 }
 636
 637 /**
 638  * gpiod_export_link - create a sysfs link to an exported GPIO node
 639  * @dev: device under which to create symlink
 640  * @name: name of the symlink
 641  * @gpio: gpio to create symlink to, already exported
 642  *
 643  * Set up a symlink from /sys/.../dev/name to /sys/class/gpio/gpioN
 644  * node. Caller is responsible for unlinking.
 645  *
 646  * Returns zero on success, else an error.
 647  */
 648 int gpiod_export_link(struct device *dev, const char *name,
 649                       struct gpio_desc *desc)
 650 {
 651         struct device *cdev;
 652         int ret;
 653
 654         if (!desc) {
 655                 pr_warn("%s: invalid GPIO\n", __func__);
 656                 return -EINVAL;
 657         }
 658
 659         cdev = class_find_device(&gpio_class, NULL, desc, match_export);
 660         if (!cdev)
 661                 return -ENODEV;
 662
 663         ret = sysfs_create_link(&dev->kobj, &cdev->kobj, name);
 664         put_device(cdev);
 665
 666         return ret;
 667 }
 668 EXPORT_SYMBOL_GPL(gpiod_export_link);
 669
 670 /**
 671  * gpiod_unexport - reverse effect of gpio_export()
 672  * @gpio: gpio to make unavailable
 673  *
 674  * This is implicit on gpio_free().
 675  */
 676 void gpiod_unexport(struct gpio_desc *desc)
 677 {
 678         struct gpiod_data *data;
 679         struct device *dev;
 680
 681         if (!desc) {
 682                 pr_warn("%s: invalid GPIO\n", __func__);
 683                 return;
 684         }
 685
 686         mutex_lock(&sysfs_lock);
 687
 688         if (!test_bit(FLAG_EXPORT, &desc->flags))
 689                 goto err_unlock;
 690
 691         dev = class_find_device(&gpio_class, NULL, desc, match_export);
 692         if (!dev)
 693                 goto err_unlock;
 694
 695         data = dev_get_drvdata(dev);
 696
 697         clear_bit(FLAG_EXPORT, &desc->flags);
 698
 699         device_unregister(dev);
 700
 701         /*
 702          * Release irq after deregistration to prevent race with edge_store.
 703          */
 704         if (data->irq_flags)
 705                 gpio_sysfs_free_irq(dev);
 706
 707         mutex_unlock(&sysfs_lock);
 708
 709         put_device(dev);
 710         kfree(data);
 711
 712         return;
 713
 714 err_unlock:
 715         mutex_unlock(&sysfs_lock);
 716 }
 717 EXPORT_SYMBOL_GPL(gpiod_unexport);
 718
 719 int gpiochip_sysfs_register(struct gpio_chip *chip)
 720 {
 721         struct device   *dev;
 722
 723         /*
 724          * Many systems add gpio chips for SOC support very early,
 725          * before driver model support is available.  In those cases we
 726          * register later, in gpiolib_sysfs_init() ... here we just
 727          * verify that _some_ field of gpio_class got initialized.
 728          */
 729         if (!gpio_class.p)
 730                 return 0;
 731
 732         /* use chip->base for the ID; it's already known to be unique */
 733         dev = device_create_with_groups(&gpio_class, chip->dev, MKDEV(0, 0),
 734                                         chip, gpiochip_groups,
 735                                         "gpiochip%d", chip->base);
 736         if (IS_ERR(dev))
 737                 return PTR_ERR(dev);
 738
 739         mutex_lock(&sysfs_lock);
 740         chip->cdev = dev;
 741         mutex_unlock(&sysfs_lock);
 742
 743         return 0;
 744 }
 745
 746 void gpiochip_sysfs_unregister(struct gpio_chip *chip)
 747 {
 748         struct gpio_desc *desc;
 749         unsigned int i;
 750
 751         if (!chip->cdev)
 752                 return;
 753
 754         device_unregister(chip->cdev);
 755
 756         /* prevent further gpiod exports */
 757         mutex_lock(&sysfs_lock);
 758         chip->cdev = NULL;
 759         mutex_unlock(&sysfs_lock);
 760
 761         /* unregister gpiod class devices owned by sysfs */
 762         for (i = 0; i < chip->ngpio; i++) {
 763                 desc = &chip->desc[i];
 764                 if (test_and_clear_bit(FLAG_SYSFS, &desc->flags))
 765                         gpiod_free(desc);
 766         }
 767 }
 768
 769 static int __init gpiolib_sysfs_init(void)
 770 {
 771         int             status;
 772         unsigned long   flags;
 773         struct gpio_chip *chip;
 774
 775         status = class_register(&gpio_class);
 776         if (status < 0)
 777                 return status;
 778
 779         /* Scan and register the gpio_chips which registered very
 780          * early (e.g. before the class_register above was called).
 781          *
 782          * We run before arch_initcall() so chip->dev nodes can have
 783          * registered, and so arch_initcall() can always gpio_export().
 784          */
 785         spin_lock_irqsave(&gpio_lock, flags);
 786         list_for_each_entry(chip, &gpio_chips, list) {
 787                 if (chip->cdev)
 788                         continue;
 789
 790                 /*
 791                  * TODO we yield gpio_lock here because
 792                  * gpiochip_sysfs_register() acquires a mutex. This is unsafe
 793                  * and needs to be fixed.
 794                  *
 795                  * Also it would be nice to use gpiochip_find() here so we
 796                  * can keep gpio_chips local to gpiolib.c, but the yield of
 797                  * gpio_lock prevents us from doing this.
 798                  */
 799                 spin_unlock_irqrestore(&gpio_lock, flags);
 800                 status = gpiochip_sysfs_register(chip);
 801                 spin_lock_irqsave(&gpio_lock, flags);
 802         }
 803         spin_unlock_irqrestore(&gpio_lock, flags);
 804
 805
 806         return status;
 807 }
 808 postcore_initcall(gpiolib_sysfs_init);