// SPDX-License-Identifier: GPL-2.0 #include <linux/idr.h> #include <linux/mutex.h> #include <linux/device.h> #include <linux/sysfs.h> #include <linux/gpio/consumer.h> #include <linux/gpio/driver.h> #include <linux/interrupt.h> #include <linux/kdev_t.h> #include <linux/slab.h> #include <linux/ctype.h> #include "gpiolib.h" #include "gpiolib-sysfs.h" #define GPIO_IRQF_TRIGGER_NONE 0 #define GPIO_IRQF_TRIGGER_FALLING BIT(0) #define GPIO_IRQF_TRIGGER_RISING BIT(1) #define GPIO_IRQF_TRIGGER_BOTH (GPIO_IRQF_TRIGGER_FALLING | \ GPIO_IRQF_TRIGGER_RISING) struct gpiod_data { struct gpio_desc *desc; struct mutex mutex; struct kernfs_node *value_kn; int irq; unsigned char irq_flags; bool direction_can_change; }; /* * Lock to serialise gpiod export and unexport, and prevent re-export of * gpiod whose chip is being unregistered. */ 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 * /edge * * configures behavior of poll(2) on /value * * available only if pin can generate IRQs on input * * is read/write as "none", "falling", "rising", or "both" * /active_low * * configures polarity of /value * * is read/write as zero/nonzero * * also affects existing and subsequent "falling" and "rising" * /edge configuration */ static ssize_t direction_show(struct device *dev, struct device_attribute *attr, char *buf) { struct gpiod_data *data = dev_get_drvdata(dev); struct gpio_desc *desc = data->desc; int value; mutex_lock(&data->mutex); gpiod_get_direction(desc); value = !!test_bit(FLAG_IS_OUT, &desc->flags); mutex_unlock(&data->mutex); return sysfs_emit(buf, "%s\n", value ? "out" : "in"); } static ssize_t direction_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t size) { struct gpiod_data *data = dev_get_drvdata(dev); struct gpio_desc *desc = data->desc; ssize_t status; mutex_lock(&data->mutex); if (sysfs_streq(buf, "high")) status = gpiod_direction_output_raw(desc, 1); else if (sysfs_streq(buf, "out") || sysfs_streq(buf, "low")) status = gpiod_direction_output_raw(desc, 0); else if (sysfs_streq(buf, "in")) status = gpiod_direction_input(desc); else status = -EINVAL; mutex_unlock(&data->mutex); return status ? : size; } static DEVICE_ATTR_RW(direction); static ssize_t value_show(struct device *dev, struct device_attribute *attr, char *buf) { struct gpiod_data *data = dev_get_drvdata(dev); struct gpio_desc *desc = data->desc; ssize_t status; mutex_lock(&data->mutex); status = gpiod_get_value_cansleep(desc); mutex_unlock(&data->mutex); if (status < 0) return status; return sysfs_emit(buf, "%zd\n", status); } static ssize_t value_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t size) { struct gpiod_data *data = dev_get_drvdata(dev); struct gpio_desc *desc = data->desc; ssize_t status; long value; status = kstrtol(buf, 0, &value); mutex_lock(&data->mutex); if (!test_bit(FLAG_IS_OUT, &desc->flags)) { status = -EPERM; } else if (status == 0) { gpiod_set_value_cansleep(desc, value); status = size; } mutex_unlock(&data->mutex); return status; } static DEVICE_ATTR_PREALLOC(value, S_IWUSR | S_IRUGO, value_show, value_store); static irqreturn_t gpio_sysfs_irq(int irq, void *priv) { struct gpiod_data *data = priv; sysfs_notify_dirent(data->value_kn); return IRQ_HANDLED; } /* Caller holds gpiod-data mutex. */ static int gpio_sysfs_request_irq(struct device *dev, unsigned char flags) { struct gpiod_data *data = dev_get_drvdata(dev); struct gpio_desc *desc = data->desc; unsigned long irq_flags; int ret; data->irq = gpiod_to_irq(desc); if (data->irq < 0) return -EIO; data->value_kn = sysfs_get_dirent(dev->kobj.sd, "value"); if (!data->value_kn) return -ENODEV; irq_flags = IRQF_SHARED; if (flags & GPIO_IRQF_TRIGGER_FALLING) irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ? IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING; if (flags & GPIO_IRQF_TRIGGER_RISING) irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ? IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING; /* * FIXME: This should be done in the irq_request_resources callback * when the irq is requested, but a few drivers currently fail * to do so. * * Remove this redundant call (along with the corresponding * unlock) when those drivers have been fixed. */ ret = gpiochip_lock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc)); if (ret < 0) goto err_put_kn; ret = request_any_context_irq(data->irq, gpio_sysfs_irq, irq_flags, "gpiolib", data); if (ret < 0) goto err_unlock; data->irq_flags = flags; return 0; err_unlock: gpiochip_unlock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc)); err_put_kn: sysfs_put(data->value_kn); return ret; } /* * Caller holds gpiod-data mutex (unless called after class-device * deregistration). */ static void gpio_sysfs_free_irq(struct device *dev) { struct gpiod_data *data = dev_get_drvdata(dev); struct gpio_desc *desc = data->desc; data->irq_flags = 0; free_irq(data->irq, data); gpiochip_unlock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc)); sysfs_put(data->value_kn); } static const char * const trigger_names[] = { [GPIO_IRQF_TRIGGER_NONE] = "none", [GPIO_IRQF_TRIGGER_FALLING] = "falling", [GPIO_IRQF_TRIGGER_RISING] = "rising", [GPIO_IRQF_TRIGGER_BOTH] = "both", }; static ssize_t edge_show(struct device *dev, struct device_attribute *attr, char *buf) { struct gpiod_data *data = dev_get_drvdata(dev); int flags; mutex_lock(&data->mutex); flags = data->irq_flags; mutex_unlock(&data->mutex); if (flags >= ARRAY_SIZE(trigger_names)) return 0; return sysfs_emit(buf, "%s\n", trigger_names[flags]); } static ssize_t edge_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t size) { struct gpiod_data *data = dev_get_drvdata(dev); ssize_t status = size; int flags; flags = sysfs_match_string(trigger_names, buf); if (flags < 0) return flags; mutex_lock(&data->mutex); if (flags == data->irq_flags) { status = size; goto out_unlock; } if (data->irq_flags) gpio_sysfs_free_irq(dev); if (flags) { status = gpio_sysfs_request_irq(dev, flags); if (!status) status = size; } out_unlock: mutex_unlock(&data->mutex); return status; } static DEVICE_ATTR_RW(edge); /* Caller holds gpiod-data mutex. */ static int gpio_sysfs_set_active_low(struct device *dev, int value) { struct gpiod_data *data = dev_get_drvdata(dev); struct gpio_desc *desc = data->desc; int status = 0; unsigned int flags = data->irq_flags; if (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) == !!value) return 0; assign_bit(FLAG_ACTIVE_LOW, &desc->flags, value); /* reconfigure poll(2) support if enabled on one edge only */ if (flags == GPIO_IRQF_TRIGGER_FALLING || flags == GPIO_IRQF_TRIGGER_RISING) { gpio_sysfs_free_irq(dev); status = gpio_sysfs_request_irq(dev, flags); } return status; } static ssize_t active_low_show(struct device *dev, struct device_attribute *attr, char *buf) { struct gpiod_data *data = dev_get_drvdata(dev); struct gpio_desc *desc = data->desc; int value; mutex_lock(&data->mutex); value = !!test_bit(FLAG_ACTIVE_LOW, &desc->flags); mutex_unlock(&data->mutex); return sysfs_emit(buf, "%d\n", value); } static ssize_t active_low_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t size) { struct gpiod_data *data = dev_get_drvdata(dev); ssize_t status; long value; status = kstrtol(buf, 0, &value); if (status) return status; mutex_lock(&data->mutex); status = gpio_sysfs_set_active_low(dev, value); mutex_unlock(&data->mutex); return status ? : size; } static DEVICE_ATTR_RW(active_low); static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr, int n) { struct device *dev = kobj_to_dev(kobj); struct gpiod_data *data = dev_get_drvdata(dev); struct gpio_desc *desc = data->desc; umode_t mode = attr->mode; bool show_direction = data->direction_can_change; if (attr == &dev_attr_direction.attr) { if (!show_direction) mode = 0; } else if (attr == &dev_attr_edge.attr) { if (gpiod_to_irq(desc) < 0) mode = 0; if (!show_direction && test_bit(FLAG_IS_OUT, &desc->flags)) mode = 0; } return mode; } static struct attribute *gpio_attrs[] = { &dev_attr_direction.attr, &dev_attr_edge.attr, &dev_attr_value.attr, &dev_attr_active_low.attr, NULL, }; static const struct attribute_group gpio_group = { .attrs = gpio_attrs, .is_visible = gpio_is_visible, }; static const struct attribute_group *gpio_groups[] = { &gpio_group, NULL }; /* * /sys/class/gpio/gpiochipN/ * /base ... matching gpio_chip.base (N) * /label ... matching gpio_chip.label * /ngpio ... matching gpio_chip.ngpio */ static ssize_t base_show(struct device *dev, struct device_attribute *attr, char *buf) { const struct gpio_chip *chip = dev_get_drvdata(dev); return sysfs_emit(buf, "%d\n", chip->base); } static DEVICE_ATTR_RO(base); static ssize_t label_show(struct device *dev, struct device_attribute *attr, char *buf) { const struct gpio_chip *chip = dev_get_drvdata(dev); return sysfs_emit(buf, "%s\n", chip->label ?: ""); } static DEVICE_ATTR_RO(label); static ssize_t ngpio_show(struct device *dev, struct device_attribute *attr, char *buf) { const struct gpio_chip *chip = dev_get_drvdata(dev); return sysfs_emit(buf, "%u\n", chip->ngpio); } static DEVICE_ATTR_RO(ngpio); static struct attribute *gpiochip_attrs[] = { &dev_attr_base.attr, &dev_attr_label.attr, &dev_attr_ngpio.attr, NULL, }; ATTRIBUTE_GROUPS(gpiochip); /* * /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, struct class_attribute *attr, const char *buf, size_t len) { long gpio; struct gpio_desc *desc; int status; struct gpio_chip *gc; int offset; status = kstrtol(buf, 0, &gpio); if (status < 0) goto done; desc = gpio_to_desc(gpio); /* reject invalid GPIOs */ if (!desc) { pr_warn("%s: invalid GPIO %ld\n", __func__, gpio); return -EINVAL; } gc = desc->gdev->chip; offset = gpio_chip_hwgpio(desc); if (!gpiochip_line_is_valid(gc, offset)) { pr_warn("%s: GPIO %ld masked\n", __func__, gpio); return -EINVAL; } /* 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 = gpiod_request_user(desc, "sysfs"); if (status) goto done; status = gpiod_set_transitory(desc, false); if (!status) { status = gpiod_export(desc, true); if (status < 0) gpiod_free(desc); else set_bit(FLAG_SYSFS, &desc->flags); } done: if (status) pr_debug("%s: status %d\n", __func__, status); return status ? : len; } static CLASS_ATTR_WO(export); static ssize_t unexport_store(struct class *class, struct class_attribute *attr, const char *buf, size_t len) { long gpio; struct gpio_desc *desc; int status; status = kstrtol(buf, 0, &gpio); if (status < 0) goto done; desc = gpio_to_desc(gpio); /* reject bogus commands (gpio_unexport ignores them) */ if (!desc) { pr_warn("%s: invalid GPIO %ld\n", __func__, gpio); return -EINVAL; } status = -EINVAL; /* 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, &desc->flags)) { status = 0; gpiod_free(desc); } done: if (status) pr_debug("%s: status %d\n", __func__, status); return status ? : len; } static CLASS_ATTR_WO(unexport); static struct attribute *gpio_class_attrs[] = { &class_attr_export.attr, &class_attr_unexport.attr, NULL, }; ATTRIBUTE_GROUPS(gpio_class); static struct class gpio_class = { .name = "gpio", .owner = THIS_MODULE, .class_groups = gpio_class_groups, }; /** * gpiod_export - export a GPIO through sysfs * @desc: 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 gpiod_export(struct gpio_desc *desc, bool direction_may_change) { struct gpio_chip *chip; struct gpio_device *gdev; struct gpiod_data *data; unsigned long flags; int status; const char *ioname = NULL; struct device *dev; int offset; /* can't export until sysfs is available ... */ if (!gpio_class.p) { pr_debug("%s: called too early!\n", __func__); return -ENOENT; } if (!desc) { pr_debug("%s: invalid gpio descriptor\n", __func__); return -EINVAL; } gdev = desc->gdev; chip = gdev->chip; mutex_lock(&sysfs_lock); /* check if chip is being removed */ if (!chip || !gdev->mockdev) { status = -ENODEV; goto err_unlock; } spin_lock_irqsave(&gpio_lock, flags); if (!test_bit(FLAG_REQUESTED, &desc->flags) || test_bit(FLAG_EXPORT, &desc->flags)) { spin_unlock_irqrestore(&gpio_lock, flags); gpiod_dbg(desc, "%s: unavailable (requested=%d, exported=%d)\n", __func__, test_bit(FLAG_REQUESTED, &desc->flags), test_bit(FLAG_EXPORT, &desc->flags)); status = -EPERM; goto err_unlock; } spin_unlock_irqrestore(&gpio_lock, flags); data = kzalloc(sizeof(*data), GFP_KERNEL); if (!data) { status = -ENOMEM; goto err_unlock; } data->desc = desc; mutex_init(&data->mutex); if (chip->direction_input && chip->direction_output) data->direction_can_change = direction_may_change; else data->direction_can_change = false; offset = gpio_chip_hwgpio(desc); if (chip->names && chip->names[offset]) ioname = chip->names[offset]; dev = device_create_with_groups(&gpio_class, &gdev->dev, MKDEV(0, 0), data, gpio_groups, ioname ? ioname : "gpio%u", desc_to_gpio(desc)); if (IS_ERR(dev)) { status = PTR_ERR(dev); goto err_free_data; } set_bit(FLAG_EXPORT, &desc->flags); mutex_unlock(&sysfs_lock); return 0; err_free_data: kfree(data); err_unlock: mutex_unlock(&sysfs_lock); gpiod_dbg(desc, "%s: status %d\n", __func__, status); return status; } EXPORT_SYMBOL_GPL(gpiod_export); static int match_export(struct device *dev, const void *desc) { struct gpiod_data *data = dev_get_drvdata(dev); return data->desc == desc; } /** * gpiod_export_link - create a sysfs link to an exported GPIO node * @dev: device under which to create symlink * @name: name of the symlink * @desc: GPIO to create symlink to, already exported * * Set up a symlink from /sys/.../dev/name to /sys/class/gpio/gpioN * node. Caller is responsible for unlinking. * * Returns zero on success, else an error. */ int gpiod_export_link(struct device *dev, const char *name, struct gpio_desc *desc) { struct device *cdev; int ret; if (!desc) { pr_warn("%s: invalid GPIO\n", __func__); return -EINVAL; } cdev = class_find_device(&gpio_class, NULL, desc, match_export); if (!cdev) return -ENODEV; ret = sysfs_create_link(&dev->kobj, &cdev->kobj, name); put_device(cdev); return ret; } EXPORT_SYMBOL_GPL(gpiod_export_link); /** * gpiod_unexport - reverse effect of gpiod_export() * @desc: GPIO to make unavailable * * This is implicit on gpiod_free(). */ void gpiod_unexport(struct gpio_desc *desc) { struct gpiod_data *data; struct device *dev; if (!desc) { pr_warn("%s: invalid GPIO\n", __func__); return; } mutex_lock(&sysfs_lock); if (!test_bit(FLAG_EXPORT, &desc->flags)) goto err_unlock; dev = class_find_device(&gpio_class, NULL, desc, match_export); if (!dev) goto err_unlock; data = dev_get_drvdata(dev); clear_bit(FLAG_EXPORT, &desc->flags); device_unregister(dev); /* * Release irq after deregistration to prevent race with edge_store. */ if (data->irq_flags) gpio_sysfs_free_irq(dev); mutex_unlock(&sysfs_lock); put_device(dev); kfree(data); return; err_unlock: mutex_unlock(&sysfs_lock); } EXPORT_SYMBOL_GPL(gpiod_unexport); int gpiochip_sysfs_register(struct gpio_device *gdev) { struct device *dev; struct device *parent; struct gpio_chip *chip = gdev->chip; /* * Many systems add gpio chips for SOC support very early, * before driver model support is available. In those cases we * register later, in gpiolib_sysfs_init() ... here we just * verify that _some_ field of gpio_class got initialized. */ if (!gpio_class.p) return 0; /* * For sysfs backward compatibility we need to preserve this * preferred parenting to the gpio_chip parent field, if set. */ if (chip->parent) parent = chip->parent; else parent = &gdev->dev; /* use chip->base for the ID; it's already known to be unique */ dev = device_create_with_groups(&gpio_class, parent, MKDEV(0, 0), chip, gpiochip_groups, GPIOCHIP_NAME "%d", chip->base); if (IS_ERR(dev)) return PTR_ERR(dev); mutex_lock(&sysfs_lock); gdev->mockdev = dev; mutex_unlock(&sysfs_lock); return 0; } void gpiochip_sysfs_unregister(struct gpio_device *gdev) { struct gpio_desc *desc; struct gpio_chip *chip = gdev->chip; if (!gdev->mockdev) return; device_unregister(gdev->mockdev); /* prevent further gpiod exports */ mutex_lock(&sysfs_lock); gdev->mockdev = NULL; mutex_unlock(&sysfs_lock); /* unregister gpiod class devices owned by sysfs */ for_each_gpio_desc_with_flag(chip, desc, FLAG_SYSFS) gpiod_free(desc); } static int __init gpiolib_sysfs_init(void) { int status; unsigned long flags; struct gpio_device *gdev; 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); list_for_each_entry(gdev, &gpio_devices, list) { if (gdev->mockdev) continue; /* * TODO we yield gpio_lock here because * gpiochip_sysfs_register() acquires a mutex. This is unsafe * and needs to be fixed. * * Also it would be nice to use gpiochip_find() here so we * can keep gpio_chips local to gpiolib.c, but the yield of * gpio_lock prevents us from doing this. */ spin_unlock_irqrestore(&gpio_lock, flags); status = gpiochip_sysfs_register(gdev); spin_lock_irqsave(&gpio_lock, flags); } spin_unlock_irqrestore(&gpio_lock, flags); return status; } postcore_initcall(gpiolib_sysfs_init);