cregit-Linux how code gets into the kernel

Release 4.14 drivers/gpio/gpiolib-sysfs.c

Directory: drivers/gpio
#include <linux/idr.h>
#include <linux/mutex.h>
#include <linux/device.h>
#include <linux/sysfs.h>
#include <linux/gpio.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 "gpiolib.h"


#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; ssize_t status; mutex_lock(&data->mutex); gpiod_get_direction(desc); status = sprintf(buf, "%s\n", test_bit(FLAG_IS_OUT, &desc->flags) ? "out" : "in"); mutex_unlock(&data->mutex); return status; }

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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; }

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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 = sprintf(buf, "%d\n", gpiod_get_value_cansleep(desc)); mutex_unlock(&data->mutex); return status; }

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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; mutex_lock(&data->mutex); if (!test_bit(FLAG_IS_OUT, &desc->flags)) { status = -EPERM; } else { long value; status = kstrtol(buf, 0, &value); if (status == 0) { gpiod_set_value_cansleep(desc, value); status = size; } } mutex_unlock(&data->mutex); return status; }

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static DEVICE_ATTR_RW(value);
static irqreturn_t gpio_sysfs_irq(int irq, void *priv) { struct gpiod_data *data = priv; sysfs_notify_dirent(data->value_kn); return IRQ_HANDLED; }

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/* 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; }

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/* * 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); }

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static const struct { const char *name; unsigned char flags; } trigger_types[] = { { "none", 0 }, { "falling", GPIO_IRQF_TRIGGER_FALLING }, { "rising", GPIO_IRQF_TRIGGER_RISING }, { "both", GPIO_IRQF_TRIGGER_BOTH }, };
static ssize_t edge_show(struct device *dev, struct device_attribute *attr, char *buf) { struct gpiod_data *data = dev_get_drvdata(dev); ssize_t status = 0; int i; mutex_lock(&data->mutex); for (i = 0; i < ARRAY_SIZE(trigger_types); i++) { if (data->irq_flags == trigger_types[i].flags) { status = sprintf(buf, "%s\n", trigger_types[i].name); break; } } mutex_unlock(&data->mutex); return status; }

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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); unsigned char flags; ssize_t status = size; int i; for (i = 0; i < ARRAY_SIZE(trigger_types); i++) { if (sysfs_streq(trigger_types[i].name, buf)) break; } if (i == ARRAY_SIZE(trigger_types)) return -EINVAL; flags = trigger_types[i].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; }

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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; if (value) set_bit(FLAG_ACTIVE_LOW, &desc->flags); else clear_bit(FLAG_ACTIVE_LOW, &desc->flags); /* 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; }

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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; ssize_t status; mutex_lock(&data->mutex); status = sprintf(buf, "%d\n", !!test_bit(FLAG_ACTIVE_LOW, &desc->flags)); mutex_unlock(&data->mutex); return status; }

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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; mutex_lock(&data->mutex); status = kstrtol(buf, 0, &value); if (status == 0) status = gpio_sysfs_set_active_low(dev, value); mutex_unlock(&data->mutex); return status ? : size; }

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static DEVICE_ATTR_RW(active_low);
static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr, int n) { struct device *dev = container_of(kobj, struct device, 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; }

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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 sprintf(buf, "%d\n", chip->base); }

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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 sprintf(buf, "%s\n", chip->label ? : ""); }

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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 sprintf(buf, "%u\n", chip->ngpio); }

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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);
static struct gpio_desc *gpio_to_valid_desc(int gpio) { return gpio_is_valid(gpio) ? gpio_to_desc(gpio) : NULL; }

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/* * /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; status = kstrtol(buf, 0, &gpio); if (status < 0) goto done; desc = gpio_to_valid_desc(gpio); /* reject invalid GPIOs */ if (!desc) { pr_warn("%s: invalid GPIO %ld\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(desc, "sysfs"); if (status < 0) { if (status == -EPROBE_DEFER) status = -ENODEV; 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; }

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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_valid_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; }

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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; }

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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; }

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/** * 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; }

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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); }

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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%d", chip->base); if (IS_ERR(dev)) return PTR_ERR(dev); mutex_lock(&sysfs_lock); gdev->mockdev = dev; mutex_unlock(&sysfs_lock); return 0; }

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Total123100.00%7100.00%


void gpiochip_sysfs_unregister(struct gpio_device *gdev) { struct gpio_desc *desc; struct gpio_chip *chip = gdev->chip; unsigned int i; 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 (i = 0; i < chip->ngpio; i++) { desc = &gdev->descs[i]; if (test_and_clear_bit(FLAG_SYSFS, &desc->flags)) gpiod_free(desc); } }

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Johan Hovold7065.42%450.00%
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Alexandre Courbot1715.89%112.50%
Total107100.00%8100.00%


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; }

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postcore_initcall(gpiolib_sysfs_init);

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Masami Hiramatsu290.89%12.94%
Bamvor Jian Zhang270.83%12.94%
Thierry Reding30.09%12.94%
Total3263100.00%34100.00%
Directory: drivers/gpio
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