diff options
Diffstat (limited to 'drivers/gpio/gpiolib.c')
| -rw-r--r-- | drivers/gpio/gpiolib.c | 1258 |
1 files changed, 1258 insertions, 0 deletions
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c new file mode 100644 index 0000000..1963ba6 --- /dev/null +++ b/drivers/gpio/gpiolib.c @@ -0,0 +1,1258 @@ +#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(). + */ +static int gpio_ensure_requested(struct gpio_desc *desc, unsigned offset) +{ + if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) { + struct gpio_chip *chip = desc->chip; + int gpio = chip->base + offset; + + 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; + } + pr_warning("GPIO-%d autorequested\n", gpio); + 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; +#if 0 //Ryan Modify for AST GPIO Feature + else if (!test_bit(FLAG_IS_OUT, &desc->flags)) { + status = -EPERM; + } else { +#else + else { +#endif + 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; + + /* 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 (status == 0) { + struct device *dev; + + dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0), + desc, "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->bus_id); + 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 */ |
