gpio: sysfs: correct error handling on 'value' attribute read.

[linux-2.6/btrfs-unstable.git] / drivers / gpio / gpiolib-sysfs.c

#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;
}

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);
        if (status < 0)
                goto err;

        status = sprintf(buf, "%d\n", status);
err:
        mutex_unlock(&data->mutex);

        return 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;

        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;
}
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 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;
}

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;
}
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;
}

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;
}

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;
}
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;
}

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);
}
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 ? : "");
}
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);
}
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;
}

/*
 * /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_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_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;
}
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%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;
        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);
        }
}

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);