gpiolib.c 31.3 KB
Newer Older
1 2 3 4
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/irq.h>
#include <linux/spinlock.h>
David Brownell's avatar
David Brownell committed
5 6 7 8 9
#include <linux/device.h>
#include <linux/err.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/gpio.h>
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48


/* Optional implementation infrastructure for GPIO interfaces.
 *
 * Platforms may want to use this if they tend to use very many GPIOs
 * that aren't part of a System-On-Chip core; or across I2C/SPI/etc.
 *
 * When kernel footprint or instruction count is an issue, simpler
 * implementations may be preferred.  The GPIO programming interface
 * allows for inlining speed-critical get/set operations for common
 * cases, so that access to SOC-integrated GPIOs can sometimes cost
 * only an instruction or two per bit.
 */


/* When debugging, extend minimal trust to callers and platform code.
 * Also emit diagnostic messages that may help initial bringup, when
 * board setup or driver bugs are most common.
 *
 * Otherwise, minimize overhead in what may be bitbanging codepaths.
 */
#ifdef	DEBUG
#define	extra_checks	1
#else
#define	extra_checks	0
#endif

/* gpio_lock prevents conflicts during gpio_desc[] table updates.
 * While any GPIO is requested, its gpio_chip is not removable;
 * each GPIO's "requested" flag serves as a lock and refcount.
 */
static DEFINE_SPINLOCK(gpio_lock);

struct gpio_desc {
	struct gpio_chip	*chip;
	unsigned long		flags;
/* flag symbols are bit numbers */
#define FLAG_REQUESTED	0
#define FLAG_IS_OUT	1
Anton Vorontsov's avatar
Anton Vorontsov committed
49
#define FLAG_RESERVED	2
David Brownell's avatar
David Brownell committed
50 51
#define FLAG_EXPORT	3	/* protected by sysfs_lock */
#define FLAG_SYSFS	4	/* exported via /sys/class/gpio/control */
52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69

#ifdef CONFIG_DEBUG_FS
	const char		*label;
#endif
};
static struct gpio_desc gpio_desc[ARCH_NR_GPIOS];

static inline void desc_set_label(struct gpio_desc *d, const char *label)
{
#ifdef CONFIG_DEBUG_FS
	d->label = label;
#endif
}

/* Warn when drivers omit gpio_request() calls -- legal but ill-advised
 * when setting direction, and otherwise illegal.  Until board setup code
 * and drivers use explicit requests everywhere (which won't happen when
 * those calls have no teeth) we can't avoid autorequesting.  This nag
David Brownell's avatar
David Brownell committed
70 71
 * message should motivate switching to explicit requests... so should
 * the weaker cleanup after faults, compared to gpio_request().
72 73 74 75
 *
 * NOTE: the autorequest mechanism is going away; at this point it's
 * only "legal" in the sense that (old) code using it won't break yet,
 * but instead only triggers a WARN() stack dump.
76
 */
David Brownell's avatar
David Brownell committed
77
static int gpio_ensure_requested(struct gpio_desc *desc, unsigned offset)
78
{
79 80
	const struct gpio_chip *chip = desc->chip;
	const int gpio = chip->base + offset;
David Brownell's avatar
David Brownell committed
81

82 83
	if (WARN(test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0,
			"autorequest GPIO-%d\n", gpio)) {
David Brownell's avatar
David Brownell committed
84 85 86 87 88 89
		if (!try_module_get(chip->owner)) {
			pr_err("GPIO-%d: module can't be gotten \n", gpio);
			clear_bit(FLAG_REQUESTED, &desc->flags);
			/* lose */
			return -EIO;
		}
90
		desc_set_label(desc, "[auto]");
David Brownell's avatar
David Brownell committed
91 92 93
		/* caller must chip->request() w/o spinlock */
		if (chip->request)
			return 1;
94
	}
David Brownell's avatar
David Brownell committed
95
	return 0;
96 97 98 99 100 101 102 103
}

/* caller holds gpio_lock *OR* gpio is marked as requested */
static inline struct gpio_chip *gpio_to_chip(unsigned gpio)
{
	return gpio_desc[gpio].chip;
}

104 105 106 107 108 109 110 111
/* dynamic allocation of GPIOs, e.g. on a hotplugged device */
static int gpiochip_find_base(int ngpio)
{
	int i;
	int spare = 0;
	int base = -ENOSPC;

	for (i = ARCH_NR_GPIOS - 1; i >= 0 ; i--) {
Anton Vorontsov's avatar
Anton Vorontsov committed
112 113
		struct gpio_desc *desc = &gpio_desc[i];
		struct gpio_chip *chip = desc->chip;
114

Anton Vorontsov's avatar
Anton Vorontsov committed
115
		if (!chip && !test_bit(FLAG_RESERVED, &desc->flags)) {
116 117 118 119 120 121 122
			spare++;
			if (spare == ngpio) {
				base = i;
				break;
			}
		} else {
			spare = 0;
Anton Vorontsov's avatar
Anton Vorontsov committed
123 124
			if (chip)
				i -= chip->ngpio - 1;
125 126 127 128 129 130 131 132
		}
	}

	if (gpio_is_valid(base))
		pr_debug("%s: found new base at %d\n", __func__, base);
	return base;
}

Anton Vorontsov's avatar
Anton Vorontsov committed
133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149
/**
 * gpiochip_reserve() - reserve range of gpios to use with platform code only
 * @start: starting gpio number
 * @ngpio: number of gpios to reserve
 * Context: platform init, potentially before irqs or kmalloc will work
 *
 * Returns a negative errno if any gpio within the range is already reserved
 * or registered, else returns zero as a success code.  Use this function
 * to mark a range of gpios as unavailable for dynamic gpio number allocation,
 * for example because its driver support is not yet loaded.
 */
int __init gpiochip_reserve(int start, int ngpio)
{
	int ret = 0;
	unsigned long flags;
	int i;

Trent Piepho's avatar
Trent Piepho committed
150
	if (!gpio_is_valid(start) || !gpio_is_valid(start + ngpio - 1))
Anton Vorontsov's avatar
Anton Vorontsov committed
151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173
		return -EINVAL;

	spin_lock_irqsave(&gpio_lock, flags);

	for (i = start; i < start + ngpio; i++) {
		struct gpio_desc *desc = &gpio_desc[i];

		if (desc->chip || test_bit(FLAG_RESERVED, &desc->flags)) {
			ret = -EBUSY;
			goto err;
		}

		set_bit(FLAG_RESERVED, &desc->flags);
	}

	pr_debug("%s: reserved gpios from %d to %d\n",
		 __func__, start, start + ngpio - 1);
err:
	spin_unlock_irqrestore(&gpio_lock, flags);

	return ret;
}

David Brownell's avatar
David Brownell committed
174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254
#ifdef CONFIG_GPIO_SYSFS

/* lock protects against unexport_gpio() being called while
 * sysfs files are active.
 */
static DEFINE_MUTEX(sysfs_lock);

/*
 * /sys/class/gpio/gpioN... only for GPIOs that are exported
 *   /direction
 *      * MAY BE OMITTED if kernel won't allow direction changes
 *      * is read/write as "in" or "out"
 *      * may also be written as "high" or "low", initializing
 *        output value as specified ("out" implies "low")
 *   /value
 *      * always readable, subject to hardware behavior
 *      * may be writable, as zero/nonzero
 *
 * REVISIT there will likely be an attribute for configuring async
 * notifications, e.g. to specify polling interval or IRQ trigger type
 * that would for example trigger a poll() on the "value".
 */

static ssize_t gpio_direction_show(struct device *dev,
		struct device_attribute *attr, char *buf)
{
	const struct gpio_desc	*desc = dev_get_drvdata(dev);
	ssize_t			status;

	mutex_lock(&sysfs_lock);

	if (!test_bit(FLAG_EXPORT, &desc->flags))
		status = -EIO;
	else
		status = sprintf(buf, "%s\n",
			test_bit(FLAG_IS_OUT, &desc->flags)
				? "out" : "in");

	mutex_unlock(&sysfs_lock);
	return status;
}

static ssize_t gpio_direction_store(struct device *dev,
		struct device_attribute *attr, const char *buf, size_t size)
{
	const struct gpio_desc	*desc = dev_get_drvdata(dev);
	unsigned		gpio = desc - gpio_desc;
	ssize_t			status;

	mutex_lock(&sysfs_lock);

	if (!test_bit(FLAG_EXPORT, &desc->flags))
		status = -EIO;
	else if (sysfs_streq(buf, "high"))
		status = gpio_direction_output(gpio, 1);
	else if (sysfs_streq(buf, "out") || sysfs_streq(buf, "low"))
		status = gpio_direction_output(gpio, 0);
	else if (sysfs_streq(buf, "in"))
		status = gpio_direction_input(gpio);
	else
		status = -EINVAL;

	mutex_unlock(&sysfs_lock);
	return status ? : size;
}

static const DEVICE_ATTR(direction, 0644,
		gpio_direction_show, gpio_direction_store);

static ssize_t gpio_value_show(struct device *dev,
		struct device_attribute *attr, char *buf)
{
	const struct gpio_desc	*desc = dev_get_drvdata(dev);
	unsigned		gpio = desc - gpio_desc;
	ssize_t			status;

	mutex_lock(&sysfs_lock);

	if (!test_bit(FLAG_EXPORT, &desc->flags))
		status = -EIO;
	else
255
		status = sprintf(buf, "%d\n", !!gpio_get_value_cansleep(gpio));
David Brownell's avatar
David Brownell committed
256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444

	mutex_unlock(&sysfs_lock);
	return status;
}

static ssize_t gpio_value_store(struct device *dev,
		struct device_attribute *attr, const char *buf, size_t size)
{
	const struct gpio_desc	*desc = dev_get_drvdata(dev);
	unsigned		gpio = desc - gpio_desc;
	ssize_t			status;

	mutex_lock(&sysfs_lock);

	if (!test_bit(FLAG_EXPORT, &desc->flags))
		status = -EIO;
	else if (!test_bit(FLAG_IS_OUT, &desc->flags))
		status = -EPERM;
	else {
		long		value;

		status = strict_strtol(buf, 0, &value);
		if (status == 0) {
			gpio_set_value_cansleep(gpio, value != 0);
			status = size;
		}
	}

	mutex_unlock(&sysfs_lock);
	return status;
}

static /*const*/ DEVICE_ATTR(value, 0644,
		gpio_value_show, gpio_value_store);

static const struct attribute *gpio_attrs[] = {
	&dev_attr_direction.attr,
	&dev_attr_value.attr,
	NULL,
};

static const struct attribute_group gpio_attr_group = {
	.attrs = (struct attribute **) gpio_attrs,
};

/*
 * /sys/class/gpio/gpiochipN/
 *   /base ... matching gpio_chip.base (N)
 *   /label ... matching gpio_chip.label
 *   /ngpio ... matching gpio_chip.ngpio
 */

static ssize_t chip_base_show(struct device *dev,
			       struct device_attribute *attr, char *buf)
{
	const struct gpio_chip	*chip = dev_get_drvdata(dev);

	return sprintf(buf, "%d\n", chip->base);
}
static DEVICE_ATTR(base, 0444, chip_base_show, NULL);

static ssize_t chip_label_show(struct device *dev,
			       struct device_attribute *attr, char *buf)
{
	const struct gpio_chip	*chip = dev_get_drvdata(dev);

	return sprintf(buf, "%s\n", chip->label ? : "");
}
static DEVICE_ATTR(label, 0444, chip_label_show, NULL);

static ssize_t chip_ngpio_show(struct device *dev,
			       struct device_attribute *attr, char *buf)
{
	const struct gpio_chip	*chip = dev_get_drvdata(dev);

	return sprintf(buf, "%u\n", chip->ngpio);
}
static DEVICE_ATTR(ngpio, 0444, chip_ngpio_show, NULL);

static const struct attribute *gpiochip_attrs[] = {
	&dev_attr_base.attr,
	&dev_attr_label.attr,
	&dev_attr_ngpio.attr,
	NULL,
};

static const struct attribute_group gpiochip_attr_group = {
	.attrs = (struct attribute **) gpiochip_attrs,
};

/*
 * /sys/class/gpio/export ... write-only
 *	integer N ... number of GPIO to export (full access)
 * /sys/class/gpio/unexport ... write-only
 *	integer N ... number of GPIO to unexport
 */
static ssize_t export_store(struct class *class, const char *buf, size_t len)
{
	long	gpio;
	int	status;

	status = strict_strtol(buf, 0, &gpio);
	if (status < 0)
		goto done;

	/* No extra locking here; FLAG_SYSFS just signifies that the
	 * request and export were done by on behalf of userspace, so
	 * they may be undone on its behalf too.
	 */

	status = gpio_request(gpio, "sysfs");
	if (status < 0)
		goto done;

	status = gpio_export(gpio, true);
	if (status < 0)
		gpio_free(gpio);
	else
		set_bit(FLAG_SYSFS, &gpio_desc[gpio].flags);

done:
	if (status)
		pr_debug("%s: status %d\n", __func__, status);
	return status ? : len;
}

static ssize_t unexport_store(struct class *class, const char *buf, size_t len)
{
	long	gpio;
	int	status;

	status = strict_strtol(buf, 0, &gpio);
	if (status < 0)
		goto done;

	status = -EINVAL;

	/* reject bogus commands (gpio_unexport ignores them) */
	if (!gpio_is_valid(gpio))
		goto done;

	/* No extra locking here; FLAG_SYSFS just signifies that the
	 * request and export were done by on behalf of userspace, so
	 * they may be undone on its behalf too.
	 */
	if (test_and_clear_bit(FLAG_SYSFS, &gpio_desc[gpio].flags)) {
		status = 0;
		gpio_free(gpio);
	}
done:
	if (status)
		pr_debug("%s: status %d\n", __func__, status);
	return status ? : len;
}

static struct class_attribute gpio_class_attrs[] = {
	__ATTR(export, 0200, NULL, export_store),
	__ATTR(unexport, 0200, NULL, unexport_store),
	__ATTR_NULL,
};

static struct class gpio_class = {
	.name =		"gpio",
	.owner =	THIS_MODULE,

	.class_attrs =	gpio_class_attrs,
};


/**
 * gpio_export - export a GPIO through sysfs
 * @gpio: gpio to make available, already requested
 * @direction_may_change: true if userspace may change gpio direction
 * Context: arch_initcall or later
 *
 * When drivers want to make a GPIO accessible to userspace after they
 * have requested it -- perhaps while debugging, or as part of their
 * public interface -- they may use this routine.  If the GPIO can
 * change direction (some can't) and the caller allows it, userspace
 * will see "direction" sysfs attribute which may be used to change
 * the gpio's direction.  A "value" attribute will always be provided.
 *
 * Returns zero on success, else an error.
 */
int gpio_export(unsigned gpio, bool direction_may_change)
{
	unsigned long		flags;
	struct gpio_desc	*desc;
	int			status = -EINVAL;
445
	char			*ioname = NULL;
David Brownell's avatar
David Brownell committed
446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468

	/* can't export until sysfs is available ... */
	if (!gpio_class.p) {
		pr_debug("%s: called too early!\n", __func__);
		return -ENOENT;
	}

	if (!gpio_is_valid(gpio))
		goto done;

	mutex_lock(&sysfs_lock);

	spin_lock_irqsave(&gpio_lock, flags);
	desc = &gpio_desc[gpio];
	if (test_bit(FLAG_REQUESTED, &desc->flags)
			&& !test_bit(FLAG_EXPORT, &desc->flags)) {
		status = 0;
		if (!desc->chip->direction_input
				|| !desc->chip->direction_output)
			direction_may_change = false;
	}
	spin_unlock_irqrestore(&gpio_lock, flags);

469 470 471
	if (desc->chip->names && desc->chip->names[gpio - desc->chip->base])
		ioname = desc->chip->names[gpio - desc->chip->base];

David Brownell's avatar
David Brownell committed
472 473 474 475
	if (status == 0) {
		struct device	*dev;

		dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0),
476
				    desc, ioname ? ioname : "gpio%d", gpio);
David Brownell's avatar
David Brownell committed
477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523
		if (dev) {
			if (direction_may_change)
				status = sysfs_create_group(&dev->kobj,
						&gpio_attr_group);
			else
				status = device_create_file(dev,
						&dev_attr_value);
			if (status != 0)
				device_unregister(dev);
		} else
			status = -ENODEV;
		if (status == 0)
			set_bit(FLAG_EXPORT, &desc->flags);
	}

	mutex_unlock(&sysfs_lock);

done:
	if (status)
		pr_debug("%s: gpio%d status %d\n", __func__, gpio, status);

	return status;
}
EXPORT_SYMBOL_GPL(gpio_export);

static int match_export(struct device *dev, void *data)
{
	return dev_get_drvdata(dev) == data;
}

/**
 * gpio_unexport - reverse effect of gpio_export()
 * @gpio: gpio to make unavailable
 *
 * This is implicit on gpio_free().
 */
void gpio_unexport(unsigned gpio)
{
	struct gpio_desc	*desc;
	int			status = -EINVAL;

	if (!gpio_is_valid(gpio))
		goto done;

	mutex_lock(&sysfs_lock);

	desc = &gpio_desc[gpio];
524

David Brownell's avatar
David Brownell committed
525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654
	if (test_bit(FLAG_EXPORT, &desc->flags)) {
		struct device	*dev = NULL;

		dev = class_find_device(&gpio_class, NULL, desc, match_export);
		if (dev) {
			clear_bit(FLAG_EXPORT, &desc->flags);
			put_device(dev);
			device_unregister(dev);
			status = 0;
		} else
			status = -ENODEV;
	}

	mutex_unlock(&sysfs_lock);
done:
	if (status)
		pr_debug("%s: gpio%d status %d\n", __func__, gpio, status);
}
EXPORT_SYMBOL_GPL(gpio_unexport);

static int gpiochip_export(struct gpio_chip *chip)
{
	int		status;
	struct device	*dev;

	/* Many systems register gpio chips for SOC support very early,
	 * before driver model support is available.  In those cases we
	 * export this later, in gpiolib_sysfs_init() ... here we just
	 * verify that _some_ field of gpio_class got initialized.
	 */
	if (!gpio_class.p)
		return 0;

	/* use chip->base for the ID; it's already known to be unique */
	mutex_lock(&sysfs_lock);
	dev = device_create(&gpio_class, chip->dev, MKDEV(0, 0), chip,
				"gpiochip%d", chip->base);
	if (dev) {
		status = sysfs_create_group(&dev->kobj,
				&gpiochip_attr_group);
	} else
		status = -ENODEV;
	chip->exported = (status == 0);
	mutex_unlock(&sysfs_lock);

	if (status) {
		unsigned long	flags;
		unsigned	gpio;

		spin_lock_irqsave(&gpio_lock, flags);
		gpio = chip->base;
		while (gpio_desc[gpio].chip == chip)
			gpio_desc[gpio++].chip = NULL;
		spin_unlock_irqrestore(&gpio_lock, flags);

		pr_debug("%s: chip %s status %d\n", __func__,
				chip->label, status);
	}

	return status;
}

static void gpiochip_unexport(struct gpio_chip *chip)
{
	int			status;
	struct device		*dev;

	mutex_lock(&sysfs_lock);
	dev = class_find_device(&gpio_class, NULL, chip, match_export);
	if (dev) {
		put_device(dev);
		device_unregister(dev);
		chip->exported = 0;
		status = 0;
	} else
		status = -ENODEV;
	mutex_unlock(&sysfs_lock);

	if (status)
		pr_debug("%s: chip %s status %d\n", __func__,
				chip->label, status);
}

static int __init gpiolib_sysfs_init(void)
{
	int		status;
	unsigned long	flags;
	unsigned	gpio;

	status = class_register(&gpio_class);
	if (status < 0)
		return status;

	/* Scan and register the gpio_chips which registered very
	 * early (e.g. before the class_register above was called).
	 *
	 * We run before arch_initcall() so chip->dev nodes can have
	 * registered, and so arch_initcall() can always gpio_export().
	 */
	spin_lock_irqsave(&gpio_lock, flags);
	for (gpio = 0; gpio < ARCH_NR_GPIOS; gpio++) {
		struct gpio_chip	*chip;

		chip = gpio_desc[gpio].chip;
		if (!chip || chip->exported)
			continue;

		spin_unlock_irqrestore(&gpio_lock, flags);
		status = gpiochip_export(chip);
		spin_lock_irqsave(&gpio_lock, flags);
	}
	spin_unlock_irqrestore(&gpio_lock, flags);


	return status;
}
postcore_initcall(gpiolib_sysfs_init);

#else
static inline int gpiochip_export(struct gpio_chip *chip)
{
	return 0;
}

static inline void gpiochip_unexport(struct gpio_chip *chip)
{
}

#endif /* CONFIG_GPIO_SYSFS */

655 656 657 658 659 660 661 662
/**
 * gpiochip_add() - register a gpio_chip
 * @chip: the chip to register, with chip->base initialized
 * Context: potentially before irqs or kmalloc will work
 *
 * Returns a negative errno if the chip can't be registered, such as
 * because the chip->base is invalid or already associated with a
 * different chip.  Otherwise it returns zero as a success code.
663
 *
David Brownell's avatar
David Brownell committed
664 665 666 667 668
 * When gpiochip_add() is called very early during boot, so that GPIOs
 * can be freely used, the chip->dev device must be registered before
 * the gpio framework's arch_initcall().  Otherwise sysfs initialization
 * for GPIOs will fail rudely.
 *
669 670
 * If chip->base is negative, this requests dynamic assignment of
 * a range of valid GPIOs.
671 672 673 674 675 676
 */
int gpiochip_add(struct gpio_chip *chip)
{
	unsigned long	flags;
	int		status = 0;
	unsigned	id;
677
	int		base = chip->base;
678

Trent Piepho's avatar
Trent Piepho committed
679
	if ((!gpio_is_valid(base) || !gpio_is_valid(base + chip->ngpio - 1))
680
			&& base >= 0) {
681 682 683 684 685 686
		status = -EINVAL;
		goto fail;
	}

	spin_lock_irqsave(&gpio_lock, flags);

687 688 689 690
	if (base < 0) {
		base = gpiochip_find_base(chip->ngpio);
		if (base < 0) {
			status = base;
David Brownell's avatar
David Brownell committed
691
			goto unlock;
692 693 694 695
		}
		chip->base = base;
	}

696
	/* these GPIO numbers must not be managed by another gpio_chip */
697
	for (id = base; id < base + chip->ngpio; id++) {
698 699 700 701 702 703
		if (gpio_desc[id].chip != NULL) {
			status = -EBUSY;
			break;
		}
	}
	if (status == 0) {
704
		for (id = base; id < base + chip->ngpio; id++) {
705
			gpio_desc[id].chip = chip;
David Brownell's avatar
David Brownell committed
706 707 708 709 710 711 712 713 714 715

			/* REVISIT:  most hardware initializes GPIOs as
			 * inputs (often with pullups enabled) so power
			 * usage is minimized.  Linux code should set the
			 * gpio direction first thing; but until it does,
			 * we may expose the wrong direction in sysfs.
			 */
			gpio_desc[id].flags = !chip->direction_input
				? (1 << FLAG_IS_OUT)
				: 0;
716 717 718
		}
	}

David Brownell's avatar
David Brownell committed
719
unlock:
720
	spin_unlock_irqrestore(&gpio_lock, flags);
David Brownell's avatar
David Brownell committed
721 722
	if (status == 0)
		status = gpiochip_export(chip);
723 724 725 726
fail:
	/* failures here can mean systems won't boot... */
	if (status)
		pr_err("gpiochip_add: gpios %d..%d (%s) not registered\n",
Trent Piepho's avatar
Trent Piepho committed
727
			chip->base, chip->base + chip->ngpio - 1,
728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758
			chip->label ? : "generic");
	return status;
}
EXPORT_SYMBOL_GPL(gpiochip_add);

/**
 * gpiochip_remove() - unregister a gpio_chip
 * @chip: the chip to unregister
 *
 * A gpio_chip with any GPIOs still requested may not be removed.
 */
int gpiochip_remove(struct gpio_chip *chip)
{
	unsigned long	flags;
	int		status = 0;
	unsigned	id;

	spin_lock_irqsave(&gpio_lock, flags);

	for (id = chip->base; id < chip->base + chip->ngpio; id++) {
		if (test_bit(FLAG_REQUESTED, &gpio_desc[id].flags)) {
			status = -EBUSY;
			break;
		}
	}
	if (status == 0) {
		for (id = chip->base; id < chip->base + chip->ngpio; id++)
			gpio_desc[id].chip = NULL;
	}

	spin_unlock_irqrestore(&gpio_lock, flags);
David Brownell's avatar
David Brownell committed
759 760 761 762

	if (status == 0)
		gpiochip_unexport(chip);

763 764 765 766 767 768 769 770 771 772 773 774
	return status;
}
EXPORT_SYMBOL_GPL(gpiochip_remove);


/* These "optional" allocation calls help prevent drivers from stomping
 * on each other, and help provide better diagnostics in debugfs.
 * They're called even less than the "set direction" calls.
 */
int gpio_request(unsigned gpio, const char *label)
{
	struct gpio_desc	*desc;
David Brownell's avatar
David Brownell committed
775
	struct gpio_chip	*chip;
776 777 778 779 780
	int			status = -EINVAL;
	unsigned long		flags;

	spin_lock_irqsave(&gpio_lock, flags);

781
	if (!gpio_is_valid(gpio))
782 783
		goto done;
	desc = &gpio_desc[gpio];
David Brownell's avatar
David Brownell committed
784 785
	chip = desc->chip;
	if (chip == NULL)
786 787
		goto done;

David Brownell's avatar
David Brownell committed
788
	if (!try_module_get(chip->owner))
789 790
		goto done;

791
	/* NOTE:  gpio_request() can be called in early boot,
David Brownell's avatar
David Brownell committed
792
	 * before IRQs are enabled, for non-sleeping (SOC) GPIOs.
793 794 795 796 797
	 */

	if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
		desc_set_label(desc, label ? : "?");
		status = 0;
798
	} else {
799
		status = -EBUSY;
David Brownell's avatar
David Brownell committed
800
		module_put(chip->owner);
801
		goto done;
David Brownell's avatar
David Brownell committed
802 803 804 805 806 807 808 809 810 811 812 813 814
	}

	if (chip->request) {
		/* chip->request may sleep */
		spin_unlock_irqrestore(&gpio_lock, flags);
		status = chip->request(chip, gpio - chip->base);
		spin_lock_irqsave(&gpio_lock, flags);

		if (status < 0) {
			desc_set_label(desc, NULL);
			module_put(chip->owner);
			clear_bit(FLAG_REQUESTED, &desc->flags);
		}
815
	}
816 817 818 819 820 821 822 823 824 825 826 827 828 829

done:
	if (status)
		pr_debug("gpio_request: gpio-%d (%s) status %d\n",
			gpio, label ? : "?", status);
	spin_unlock_irqrestore(&gpio_lock, flags);
	return status;
}
EXPORT_SYMBOL_GPL(gpio_request);

void gpio_free(unsigned gpio)
{
	unsigned long		flags;
	struct gpio_desc	*desc;
David Brownell's avatar
David Brownell committed
830
	struct gpio_chip	*chip;
831

832 833
	might_sleep();

834
	if (!gpio_is_valid(gpio)) {
835 836 837 838
		WARN_ON(extra_checks);
		return;
	}

David Brownell's avatar
David Brownell committed
839 840
	gpio_unexport(gpio);

841 842 843
	spin_lock_irqsave(&gpio_lock, flags);

	desc = &gpio_desc[gpio];
David Brownell's avatar
David Brownell committed
844 845 846 847 848 849 850 851
	chip = desc->chip;
	if (chip && test_bit(FLAG_REQUESTED, &desc->flags)) {
		if (chip->free) {
			spin_unlock_irqrestore(&gpio_lock, flags);
			might_sleep_if(extra_checks && chip->can_sleep);
			chip->free(chip, gpio - chip->base);
			spin_lock_irqsave(&gpio_lock, flags);
		}
852
		desc_set_label(desc, NULL);
853
		module_put(desc->chip->owner);
David Brownell's avatar
David Brownell committed
854
		clear_bit(FLAG_REQUESTED, &desc->flags);
855
	} else
856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879
		WARN_ON(extra_checks);

	spin_unlock_irqrestore(&gpio_lock, flags);
}
EXPORT_SYMBOL_GPL(gpio_free);


/**
 * gpiochip_is_requested - return string iff signal was requested
 * @chip: controller managing the signal
 * @offset: of signal within controller's 0..(ngpio - 1) range
 *
 * Returns NULL if the GPIO is not currently requested, else a string.
 * If debugfs support is enabled, the string returned is the label passed
 * to gpio_request(); otherwise it is a meaningless constant.
 *
 * This function is for use by GPIO controller drivers.  The label can
 * help with diagnostics, and knowing that the signal is used as a GPIO
 * can help avoid accidentally multiplexing it to another controller.
 */
const char *gpiochip_is_requested(struct gpio_chip *chip, unsigned offset)
{
	unsigned gpio = chip->base + offset;

880
	if (!gpio_is_valid(gpio) || gpio_desc[gpio].chip != chip)
881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910
		return NULL;
	if (test_bit(FLAG_REQUESTED, &gpio_desc[gpio].flags) == 0)
		return NULL;
#ifdef CONFIG_DEBUG_FS
	return gpio_desc[gpio].label;
#else
	return "?";
#endif
}
EXPORT_SYMBOL_GPL(gpiochip_is_requested);


/* Drivers MUST set GPIO direction before making get/set calls.  In
 * some cases this is done in early boot, before IRQs are enabled.
 *
 * As a rule these aren't called more than once (except for drivers
 * using the open-drain emulation idiom) so these are natural places
 * to accumulate extra debugging checks.  Note that we can't (yet)
 * rely on gpio_request() having been called beforehand.
 */

int gpio_direction_input(unsigned gpio)
{
	unsigned long		flags;
	struct gpio_chip	*chip;
	struct gpio_desc	*desc = &gpio_desc[gpio];
	int			status = -EINVAL;

	spin_lock_irqsave(&gpio_lock, flags);

911
	if (!gpio_is_valid(gpio))
912 913 914 915 916 917 918
		goto fail;
	chip = desc->chip;
	if (!chip || !chip->get || !chip->direction_input)
		goto fail;
	gpio -= chip->base;
	if (gpio >= chip->ngpio)
		goto fail;
David Brownell's avatar
David Brownell committed
919 920 921
	status = gpio_ensure_requested(desc, gpio);
	if (status < 0)
		goto fail;
922 923 924 925 926 927 928

	/* now we know the gpio is valid and chip won't vanish */

	spin_unlock_irqrestore(&gpio_lock, flags);

	might_sleep_if(extra_checks && chip->can_sleep);

David Brownell's avatar
David Brownell committed
929 930 931 932 933 934 935 936 937 938 939 940
	if (status) {
		status = chip->request(chip, gpio);
		if (status < 0) {
			pr_debug("GPIO-%d: chip request fail, %d\n",
				chip->base + gpio, status);
			/* and it's not available to anyone else ...
			 * gpio_request() is the fully clean solution.
			 */
			goto lose;
		}
	}

941 942 943
	status = chip->direction_input(chip, gpio);
	if (status == 0)
		clear_bit(FLAG_IS_OUT, &desc->flags);
David Brownell's avatar
David Brownell committed
944
lose:
945 946 947 948 949
	return status;
fail:
	spin_unlock_irqrestore(&gpio_lock, flags);
	if (status)
		pr_debug("%s: gpio-%d status %d\n",
950
			__func__, gpio, status);
951 952 953 954 955 956 957 958 959 960 961 962 963
	return status;
}
EXPORT_SYMBOL_GPL(gpio_direction_input);

int gpio_direction_output(unsigned gpio, int value)
{
	unsigned long		flags;
	struct gpio_chip	*chip;
	struct gpio_desc	*desc = &gpio_desc[gpio];
	int			status = -EINVAL;

	spin_lock_irqsave(&gpio_lock, flags);

964
	if (!gpio_is_valid(gpio))
965 966 967 968 969 970 971
		goto fail;
	chip = desc->chip;
	if (!chip || !chip->set || !chip->direction_output)
		goto fail;
	gpio -= chip->base;
	if (gpio >= chip->ngpio)
		goto fail;
David Brownell's avatar
David Brownell committed
972 973 974
	status = gpio_ensure_requested(desc, gpio);
	if (status < 0)
		goto fail;
975 976 977 978 979 980 981

	/* now we know the gpio is valid and chip won't vanish */

	spin_unlock_irqrestore(&gpio_lock, flags);

	might_sleep_if(extra_checks && chip->can_sleep);

David Brownell's avatar
David Brownell committed
982 983 984 985 986 987 988 989 990 991 992 993
	if (status) {
		status = chip->request(chip, gpio);
		if (status < 0) {
			pr_debug("GPIO-%d: chip request fail, %d\n",
				chip->base + gpio, status);
			/* and it's not available to anyone else ...
			 * gpio_request() is the fully clean solution.
			 */
			goto lose;
		}
	}

994 995 996
	status = chip->direction_output(chip, gpio, value);
	if (status == 0)
		set_bit(FLAG_IS_OUT, &desc->flags);
David Brownell's avatar
David Brownell committed
997
lose:
998 999 1000 1001 1002
	return status;
fail:
	spin_unlock_irqrestore(&gpio_lock, flags);
	if (status)
		pr_debug("%s: gpio-%d status %d\n",
1003
			__func__, gpio, status);
1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087
	return status;
}
EXPORT_SYMBOL_GPL(gpio_direction_output);


/* I/O calls are only valid after configuration completed; the relevant
 * "is this a valid GPIO" error checks should already have been done.
 *
 * "Get" operations are often inlinable as reading a pin value register,
 * and masking the relevant bit in that register.
 *
 * When "set" operations are inlinable, they involve writing that mask to
 * one register to set a low value, or a different register to set it high.
 * Otherwise locking is needed, so there may be little value to inlining.
 *
 *------------------------------------------------------------------------
 *
 * IMPORTANT!!!  The hot paths -- get/set value -- assume that callers
 * have requested the GPIO.  That can include implicit requesting by
 * a direction setting call.  Marking a gpio as requested locks its chip
 * in memory, guaranteeing that these table lookups need no more locking
 * and that gpiochip_remove() will fail.
 *
 * REVISIT when debugging, consider adding some instrumentation to ensure
 * that the GPIO was actually requested.
 */

/**
 * __gpio_get_value() - return a gpio's value
 * @gpio: gpio whose value will be returned
 * Context: any
 *
 * This is used directly or indirectly to implement gpio_get_value().
 * It returns the zero or nonzero value provided by the associated
 * gpio_chip.get() method; or zero if no such method is provided.
 */
int __gpio_get_value(unsigned gpio)
{
	struct gpio_chip	*chip;

	chip = gpio_to_chip(gpio);
	WARN_ON(extra_checks && chip->can_sleep);
	return chip->get ? chip->get(chip, gpio - chip->base) : 0;
}
EXPORT_SYMBOL_GPL(__gpio_get_value);

/**
 * __gpio_set_value() - assign a gpio's value
 * @gpio: gpio whose value will be assigned
 * @value: value to assign
 * Context: any
 *
 * This is used directly or indirectly to implement gpio_set_value().
 * It invokes the associated gpio_chip.set() method.
 */
void __gpio_set_value(unsigned gpio, int value)
{
	struct gpio_chip	*chip;

	chip = gpio_to_chip(gpio);
	WARN_ON(extra_checks && chip->can_sleep);
	chip->set(chip, gpio - chip->base, value);
}
EXPORT_SYMBOL_GPL(__gpio_set_value);

/**
 * __gpio_cansleep() - report whether gpio value access will sleep
 * @gpio: gpio in question
 * Context: any
 *
 * This is used directly or indirectly to implement gpio_cansleep().  It
 * returns nonzero if access reading or writing the GPIO value can sleep.
 */
int __gpio_cansleep(unsigned gpio)
{
	struct gpio_chip	*chip;

	/* only call this on GPIOs that are valid! */
	chip = gpio_to_chip(gpio);

	return chip->can_sleep;
}
EXPORT_SYMBOL_GPL(__gpio_cansleep);

David Brownell's avatar
David Brownell committed
1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105
/**
 * __gpio_to_irq() - return the IRQ corresponding to a GPIO
 * @gpio: gpio whose IRQ will be returned (already requested)
 * Context: any
 *
 * This is used directly or indirectly to implement gpio_to_irq().
 * It returns the number of the IRQ signaled by this (input) GPIO,
 * or a negative errno.
 */
int __gpio_to_irq(unsigned gpio)
{
	struct gpio_chip	*chip;

	chip = gpio_to_chip(gpio);
	return chip->to_irq ? chip->to_irq(chip, gpio - chip->base) : -ENXIO;
}
EXPORT_SYMBOL_GPL(__gpio_to_irq);

1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117


/* There's no value in making it easy to inline GPIO calls that may sleep.
 * Common examples include ones connected to I2C or SPI chips.
 */

int gpio_get_value_cansleep(unsigned gpio)
{
	struct gpio_chip	*chip;

	might_sleep_if(extra_checks);
	chip = gpio_to_chip(gpio);
1118
	return chip->get ? chip->get(chip, gpio - chip->base) : 0;
1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146
}
EXPORT_SYMBOL_GPL(gpio_get_value_cansleep);

void gpio_set_value_cansleep(unsigned gpio, int value)
{
	struct gpio_chip	*chip;

	might_sleep_if(extra_checks);
	chip = gpio_to_chip(gpio);
	chip->set(chip, gpio - chip->base, value);
}
EXPORT_SYMBOL_GPL(gpio_set_value_cansleep);


#ifdef CONFIG_DEBUG_FS

static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip)
{
	unsigned		i;
	unsigned		gpio = chip->base;
	struct gpio_desc	*gdesc = &gpio_desc[gpio];
	int			is_out;

	for (i = 0; i < chip->ngpio; i++, gpio++, gdesc++) {
		if (!test_bit(FLAG_REQUESTED, &gdesc->flags))
			continue;

		is_out = test_bit(FLAG_IS_OUT, &gdesc->flags);
1147
		seq_printf(s, " gpio-%-3d (%-20.20s) %s %s",
1148 1149 1150 1151 1152 1153 1154 1155
			gpio, gdesc->label,
			is_out ? "out" : "in ",
			chip->get
				? (chip->get(chip, i) ? "hi" : "lo")
				: "?  ");

		if (!is_out) {
			int		irq = gpio_to_irq(gpio);
1156
			struct irq_desc	*desc = irq_to_desc(irq);
1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209

			/* This races with request_irq(), set_irq_type(),
			 * and set_irq_wake() ... but those are "rare".
			 *
			 * More significantly, trigger type flags aren't
			 * currently maintained by genirq.
			 */
			if (irq >= 0 && desc->action) {
				char *trigger;

				switch (desc->status & IRQ_TYPE_SENSE_MASK) {
				case IRQ_TYPE_NONE:
					trigger = "(default)";
					break;
				case IRQ_TYPE_EDGE_FALLING:
					trigger = "edge-falling";
					break;
				case IRQ_TYPE_EDGE_RISING:
					trigger = "edge-rising";
					break;
				case IRQ_TYPE_EDGE_BOTH:
					trigger = "edge-both";
					break;
				case IRQ_TYPE_LEVEL_HIGH:
					trigger = "level-high";
					break;
				case IRQ_TYPE_LEVEL_LOW:
					trigger = "level-low";
					break;
				default:
					trigger = "?trigger?";
					break;
				}

				seq_printf(s, " irq-%d %s%s",
					irq, trigger,
					(desc->status & IRQ_WAKEUP)
						? " wakeup" : "");
			}
		}

		seq_printf(s, "\n");
	}
}

static int gpiolib_show(struct seq_file *s, void *unused)
{
	struct gpio_chip	*chip = NULL;
	unsigned		gpio;
	int			started = 0;

	/* REVISIT this isn't locked against gpio_chip removal ... */

1210
	for (gpio = 0; gpio_is_valid(gpio); gpio++) {
David Brownell's avatar
David Brownell committed
1211 1212
		struct device *dev;

1213 1214 1215 1216 1217 1218
		if (chip == gpio_desc[gpio].chip)
			continue;
		chip = gpio_desc[gpio].chip;
		if (!chip)
			continue;

David Brownell's avatar
David Brownell committed
1219
		seq_printf(s, "%sGPIOs %d-%d",
1220
				started ? "\n" : "",
David Brownell's avatar
David Brownell committed
1221 1222 1223 1224 1225
				chip->base, chip->base + chip->ngpio - 1);
		dev = chip->dev;
		if (dev)
			seq_printf(s, ", %s/%s",
				dev->bus ? dev->bus->name : "no-bus",
1226
				dev_name(dev));
David Brownell's avatar
David Brownell committed
1227 1228 1229 1230 1231 1232
		if (chip->label)
			seq_printf(s, ", %s", chip->label);
		if (chip->can_sleep)
			seq_printf(s, ", can sleep");
		seq_printf(s, ":\n");

1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263
		started = 1;
		if (chip->dbg_show)
			chip->dbg_show(s, chip);
		else
			gpiolib_dbg_show(s, chip);
	}
	return 0;
}

static int gpiolib_open(struct inode *inode, struct file *file)
{
	return single_open(file, gpiolib_show, NULL);
}

static struct file_operations gpiolib_operations = {
	.open		= gpiolib_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

static int __init gpiolib_debugfs_init(void)
{
	/* /sys/kernel/debug/gpio */
	(void) debugfs_create_file("gpio", S_IFREG | S_IRUGO,
				NULL, NULL, &gpiolib_operations);
	return 0;
}
subsys_initcall(gpiolib_debugfs_init);

#endif	/* DEBUG_FS */