#include <linux/kernel.h> #include <linux/module.h> #include <linux/irq.h> #include <linux/spinlock.h> #include <linux/device.h> #include <linux/err.h> #include <linux/debugfs.h> #include <linux/seq_file.h> #include <linux/gpio.h> /* 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 #define FLAG_RESERVED 2 #define FLAG_EXPORT 3 /* protected by sysfs_lock */ #define FLAG_SYSFS 4 /* exported via /sys/class/gpio/control */ #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 * message should motivate switching to explicit requests... so should * the weaker cleanup after faults, compared to gpio_request(). * * 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. */ static int gpio_ensure_requested(struct gpio_desc *desc, unsigned offset) { const struct gpio_chip *chip = desc->chip; const int gpio = chip->base + offset; if (WARN(test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0, "autorequest GPIO-%d\n", gpio)) { 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; } desc_set_label(desc, "[auto]"); /* caller must chip->request() w/o spinlock */ if (chip->request) return 1; } return 0; } /* 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; } /* 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--) { struct gpio_desc *desc = &gpio_desc[i]; struct gpio_chip *chip = desc->chip; if (!chip && !test_bit(FLAG_RESERVED, &desc->flags)) { spare++; if (spare == ngpio) { base = i; break; } } else { spare = 0; if (chip) i -= chip->ngpio - 1; } } if (gpio_is_valid(base)) pr_debug("%s: found new base at %d\n", __func__, base); return base; } /** * 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; if (!gpio_is_valid(start) || !gpio_is_valid(start + ngpio - 1)) 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; } #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 status = sprintf(buf, "%d\n", !!gpio_get_value_cansleep(gpio)); 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; char *ioname = NULL; /* 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); if (desc->chip->names && desc->chip->names[gpio - desc->chip->base]) ioname = desc->chip->names[gpio - desc->chip->base]; if (status == 0) { struct device *dev; dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0), desc, ioname ? ioname : "gpio%d", gpio); 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]; 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 */ /** * 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. * * 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. * * If chip->base is negative, this requests dynamic assignment of * a range of valid GPIOs. */ int gpiochip_add(struct gpio_chip *chip) { unsigned long flags; int status = 0; unsigned id; int base = chip->base; if ((!gpio_is_valid(base) || !gpio_is_valid(base + chip->ngpio - 1)) && base >= 0) { status = -EINVAL; goto fail; } spin_lock_irqsave(&gpio_lock, flags); if (base < 0) { base = gpiochip_find_base(chip->ngpio); if (base < 0) { status = base; goto unlock; } chip->base = base; } /* these GPIO numbers must not be managed by another gpio_chip */ for (id = base; id < base + chip->ngpio; id++) { if (gpio_desc[id].chip != NULL) { status = -EBUSY; break; } } if (status == 0) { for (id = base; id < base + chip->ngpio; id++) { gpio_desc[id].chip = chip; /* 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; } } unlock: spin_unlock_irqrestore(&gpio_lock, flags); if (status == 0) status = gpiochip_export(chip); fail: /* failures here can mean systems won't boot... */ if (status) pr_err("gpiochip_add: gpios %d..%d (%s) not registered\n", chip->base, chip->base + chip->ngpio - 1, 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); if (status == 0) gpiochip_unexport(chip); 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; struct gpio_chip *chip; int status = -EINVAL; unsigned long flags; spin_lock_irqsave(&gpio_lock, flags); if (!gpio_is_valid(gpio)) goto done; desc = &gpio_desc[gpio]; chip = desc->chip; if (chip == NULL) goto done; if (!try_module_get(chip->owner)) goto done; /* NOTE: gpio_request() can be called in early boot, * before IRQs are enabled, for non-sleeping (SOC) GPIOs. */ if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) { desc_set_label(desc, label ? : "?"); status = 0; } else { status = -EBUSY; module_put(chip->owner); goto done; } 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); } } 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; struct gpio_chip *chip; might_sleep(); if (!gpio_is_valid(gpio)) { WARN_ON(extra_checks); return; } gpio_unexport(gpio); spin_lock_irqsave(&gpio_lock, flags); desc = &gpio_desc[gpio]; 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); } desc_set_label(desc, NULL); module_put(desc->chip->owner); clear_bit(FLAG_REQUESTED, &desc->flags); } else 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; if (!gpio_is_valid(gpio) || gpio_desc[gpio].chip != chip) 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); if (!gpio_is_valid(gpio)) goto fail; chip = desc->chip; if (!chip || !chip->get || !chip->direction_input) goto fail; gpio -= chip->base; if (gpio >= chip->ngpio) goto fail; status = gpio_ensure_requested(desc, gpio); if (status < 0) goto fail; /* 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); 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; } } status = chip->direction_input(chip, gpio); if (status == 0) clear_bit(FLAG_IS_OUT, &desc->flags); lose: return status; fail: spin_unlock_irqrestore(&gpio_lock, flags); if (status) pr_debug("%s: gpio-%d status %d\n", __func__, gpio, status); 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); if (!gpio_is_valid(gpio)) goto fail; chip = desc->chip; if (!chip || !chip->set || !chip->direction_output) goto fail; gpio -= chip->base; if (gpio >= chip->ngpio) goto fail; status = gpio_ensure_requested(desc, gpio); if (status < 0) goto fail; /* 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); 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; } } status = chip->direction_output(chip, gpio, value); if (status == 0) set_bit(FLAG_IS_OUT, &desc->flags); lose: return status; fail: spin_unlock_irqrestore(&gpio_lock, flags); if (status) pr_debug("%s: gpio-%d status %d\n", __func__, gpio, status); 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); /** * __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); /* 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); return chip->get ? chip->get(chip, gpio - chip->base) : 0; } 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); seq_printf(s, " gpio-%-3d (%-20.20s) %s %s", gpio, gdesc->label, is_out ? "out" : "in ", chip->get ? (chip->get(chip, i) ? "hi" : "lo") : "? "); if (!is_out) { int irq = gpio_to_irq(gpio); struct irq_desc *desc = irq_to_desc(irq); /* 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 ... */ for (gpio = 0; gpio_is_valid(gpio); gpio++) { struct device *dev; if (chip == gpio_desc[gpio].chip) continue; chip = gpio_desc[gpio].chip; if (!chip) continue; seq_printf(s, "%sGPIOs %d-%d", started ? "\n" : "", chip->base, chip->base + chip->ngpio - 1); dev = chip->dev; if (dev) seq_printf(s, ", %s/%s", dev->bus ? dev->bus->name : "no-bus", dev_name(dev)); if (chip->label) seq_printf(s, ", %s", chip->label); if (chip->can_sleep) seq_printf(s, ", can sleep"); seq_printf(s, ":\n"); 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 */