diff options
Diffstat (limited to 'drivers/gpio/gpiolib-sysfs.c')
| -rw-r--r-- | drivers/gpio/gpiolib-sysfs.c | 820 |
1 files changed, 820 insertions, 0 deletions
diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c new file mode 100644 index 000000000..a64648682 --- /dev/null +++ b/drivers/gpio/gpiolib-sysfs.c @@ -0,0 +1,820 @@ +// 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) { + gpiod_free(desc); + goto done; + } + + 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); |