Merge tag 'trace-printf-v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/trace...

[drm/drm-misc.git] / drivers / w1 / w1.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (c) 2004 Evgeniy Polyakov <zbr@ioremap.net>
 */

#include <linux/delay.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/list.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/timer.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/hwmon.h>
#include <linux/of.h>

#include <linux/atomic.h>

#include "w1_internal.h"
#include "w1_netlink.h"

#define W1_FAMILY_DEFAULT       0
#define W1_FAMILY_DS28E04       0x1C /* for crc quirk */


static int w1_timeout = 10;
module_param_named(timeout, w1_timeout, int, 0);
MODULE_PARM_DESC(timeout, "time in seconds between automatic slave searches");

static int w1_timeout_us;
module_param_named(timeout_us, w1_timeout_us, int, 0);
MODULE_PARM_DESC(timeout_us,
                 "time in microseconds between automatic slave searches");

/* A search stops when w1_max_slave_count devices have been found in that
 * search.  The next search will start over and detect the same set of devices
 * on a static 1-wire bus.  Memory is not allocated based on this number, just
 * on the number of devices known to the kernel.  Having a high number does not
 * consume additional resources.  As a special case, if there is only one
 * device on the network and w1_max_slave_count is set to 1, the device id can
 * be read directly skipping the normal slower search process.
 */
int w1_max_slave_count = 64;
module_param_named(max_slave_count, w1_max_slave_count, int, 0);
MODULE_PARM_DESC(max_slave_count,
        "maximum number of slaves detected in a search");

int w1_max_slave_ttl = 10;
module_param_named(slave_ttl, w1_max_slave_ttl, int, 0);
MODULE_PARM_DESC(slave_ttl,
        "Number of searches not seeing a slave before it will be removed");

DEFINE_MUTEX(w1_mlock);
LIST_HEAD(w1_masters);

static int w1_master_probe(struct device *dev)
{
        return -ENODEV;
}

static void w1_master_release(struct device *dev)
{
        struct w1_master *md = dev_to_w1_master(dev);

        dev_dbg(dev, "%s: Releasing %s.\n", __func__, md->name);
        memset(md, 0, sizeof(struct w1_master) + sizeof(struct w1_bus_master));
        kfree(md);
}

static void w1_slave_release(struct device *dev)
{
        struct w1_slave *sl = dev_to_w1_slave(dev);

        dev_dbg(dev, "%s: Releasing %s [%p]\n", __func__, sl->name, sl);

        w1_family_put(sl->family);
        sl->master->slave_count--;
}

static ssize_t name_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct w1_slave *sl = dev_to_w1_slave(dev);

        return sprintf(buf, "%s\n", sl->name);
}
static DEVICE_ATTR_RO(name);

static ssize_t id_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct w1_slave *sl = dev_to_w1_slave(dev);
        ssize_t count = sizeof(sl->reg_num);

        memcpy(buf, (u8 *)&sl->reg_num, count);
        return count;
}
static DEVICE_ATTR_RO(id);

static struct attribute *w1_slave_attrs[] = {
        &dev_attr_name.attr,
        &dev_attr_id.attr,
        NULL,
};
ATTRIBUTE_GROUPS(w1_slave);

/* Default family */

static ssize_t rw_write(struct file *filp, struct kobject *kobj,
                        struct bin_attribute *bin_attr, char *buf, loff_t off,
                        size_t count)
{
        struct w1_slave *sl = kobj_to_w1_slave(kobj);

        mutex_lock(&sl->master->mutex);
        if (w1_reset_select_slave(sl)) {
                count = 0;
                goto out_up;
        }

        w1_write_block(sl->master, buf, count);

out_up:
        mutex_unlock(&sl->master->mutex);
        return count;
}

static ssize_t rw_read(struct file *filp, struct kobject *kobj,
                       struct bin_attribute *bin_attr, char *buf, loff_t off,
                       size_t count)
{
        struct w1_slave *sl = kobj_to_w1_slave(kobj);

        mutex_lock(&sl->master->mutex);
        w1_read_block(sl->master, buf, count);
        mutex_unlock(&sl->master->mutex);
        return count;
}

static BIN_ATTR_RW(rw, PAGE_SIZE);

static struct bin_attribute *w1_slave_bin_attrs[] = {
        &bin_attr_rw,
        NULL,
};

static const struct attribute_group w1_slave_default_group = {
        .bin_attrs = w1_slave_bin_attrs,
};

static const struct attribute_group *w1_slave_default_groups[] = {
        &w1_slave_default_group,
        NULL,
};

static const struct w1_family_ops w1_default_fops = {
        .groups         = w1_slave_default_groups,
};

static struct w1_family w1_default_family = {
        .fops = &w1_default_fops,
};

static int w1_uevent(const struct device *dev, struct kobj_uevent_env *env);

static const struct bus_type w1_bus_type = {
        .name = "w1",
        .uevent = w1_uevent,
};

struct device_driver w1_master_driver = {
        .name = "w1_master_driver",
        .bus = &w1_bus_type,
        .probe = w1_master_probe,
};

struct device w1_master_device = {
        .parent = NULL,
        .bus = &w1_bus_type,
        .init_name = "w1 bus master",
        .driver = &w1_master_driver,
        .release = &w1_master_release
};

static struct device_driver w1_slave_driver = {
        .name = "w1_slave_driver",
        .bus = &w1_bus_type,
};

#if 0
struct device w1_slave_device = {
        .parent = NULL,
        .bus = &w1_bus_type,
        .init_name = "w1 bus slave",
        .driver = &w1_slave_driver,
        .release = &w1_slave_release
};
#endif  /*  0  */

static ssize_t w1_master_attribute_show_name(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct w1_master *md = dev_to_w1_master(dev);
        ssize_t count;

        mutex_lock(&md->mutex);
        count = sprintf(buf, "%s\n", md->name);
        mutex_unlock(&md->mutex);

        return count;
}

static ssize_t w1_master_attribute_store_search(struct device * dev,
                                                struct device_attribute *attr,
                                                const char * buf, size_t count)
{
        long tmp;
        struct w1_master *md = dev_to_w1_master(dev);
        int ret;

        ret = kstrtol(buf, 0, &tmp);
        if (ret)
                return ret;

        mutex_lock(&md->mutex);
        md->search_count = tmp;
        mutex_unlock(&md->mutex);
        /* Only wake if it is going to be searching. */
        if (tmp)
                wake_up_process(md->thread);

        return count;
}

static ssize_t w1_master_attribute_show_search(struct device *dev,
                                               struct device_attribute *attr,
                                               char *buf)
{
        struct w1_master *md = dev_to_w1_master(dev);
        ssize_t count;

        mutex_lock(&md->mutex);
        count = sprintf(buf, "%d\n", md->search_count);
        mutex_unlock(&md->mutex);

        return count;
}

static ssize_t w1_master_attribute_store_pullup(struct device *dev,
                                                struct device_attribute *attr,
                                                const char *buf, size_t count)
{
        long tmp;
        struct w1_master *md = dev_to_w1_master(dev);
        int ret;

        ret = kstrtol(buf, 0, &tmp);
        if (ret)
                return ret;

        mutex_lock(&md->mutex);
        md->enable_pullup = tmp;
        mutex_unlock(&md->mutex);

        return count;
}

static ssize_t w1_master_attribute_show_pullup(struct device *dev,
                                               struct device_attribute *attr,
                                               char *buf)
{
        struct w1_master *md = dev_to_w1_master(dev);
        ssize_t count;

        mutex_lock(&md->mutex);
        count = sprintf(buf, "%d\n", md->enable_pullup);
        mutex_unlock(&md->mutex);

        return count;
}

static ssize_t w1_master_attribute_show_pointer(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct w1_master *md = dev_to_w1_master(dev);
        ssize_t count;

        mutex_lock(&md->mutex);
        count = sprintf(buf, "0x%p\n", md->bus_master);
        mutex_unlock(&md->mutex);
        return count;
}

static ssize_t w1_master_attribute_show_timeout(struct device *dev, struct device_attribute *attr, char *buf)
{
        return sprintf(buf, "%d\n", w1_timeout);
}

static ssize_t w1_master_attribute_show_timeout_us(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        return sprintf(buf, "%d\n", w1_timeout_us);
}

static ssize_t w1_master_attribute_store_max_slave_count(struct device *dev,
        struct device_attribute *attr, const char *buf, size_t count)
{
        int tmp;
        struct w1_master *md = dev_to_w1_master(dev);

        if (kstrtoint(buf, 0, &tmp) || tmp < 1)
                return -EINVAL;

        mutex_lock(&md->mutex);
        md->max_slave_count = tmp;
        /* allow each time the max_slave_count is updated */
        clear_bit(W1_WARN_MAX_COUNT, &md->flags);
        mutex_unlock(&md->mutex);

        return count;
}

static ssize_t w1_master_attribute_show_max_slave_count(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct w1_master *md = dev_to_w1_master(dev);
        ssize_t count;

        mutex_lock(&md->mutex);
        count = sprintf(buf, "%d\n", md->max_slave_count);
        mutex_unlock(&md->mutex);
        return count;
}

static ssize_t w1_master_attribute_show_attempts(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct w1_master *md = dev_to_w1_master(dev);
        ssize_t count;

        mutex_lock(&md->mutex);
        count = sprintf(buf, "%lu\n", md->attempts);
        mutex_unlock(&md->mutex);
        return count;
}

static ssize_t w1_master_attribute_show_slave_count(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct w1_master *md = dev_to_w1_master(dev);
        ssize_t count;

        mutex_lock(&md->mutex);
        count = sprintf(buf, "%d\n", md->slave_count);
        mutex_unlock(&md->mutex);
        return count;
}

static ssize_t w1_master_attribute_show_slaves(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        struct w1_master *md = dev_to_w1_master(dev);
        int c = PAGE_SIZE;
        struct list_head *ent, *n;
        struct w1_slave *sl = NULL;

        mutex_lock(&md->list_mutex);

        list_for_each_safe(ent, n, &md->slist) {
                sl = list_entry(ent, struct w1_slave, w1_slave_entry);

                c -= snprintf(buf + PAGE_SIZE - c, c, "%s\n", sl->name);
        }
        if (!sl)
                c -= snprintf(buf + PAGE_SIZE - c, c, "not found.\n");

        mutex_unlock(&md->list_mutex);

        return PAGE_SIZE - c;
}

static ssize_t w1_master_attribute_show_add(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        int c = PAGE_SIZE;
        c -= snprintf(buf+PAGE_SIZE - c, c,
                "write device id xx-xxxxxxxxxxxx to add slave\n");
        return PAGE_SIZE - c;
}

static int w1_atoreg_num(struct device *dev, const char *buf, size_t count,
        struct w1_reg_num *rn)
{
        unsigned int family;
        unsigned long long id;
        int i;
        u64 rn64_le;

        /* The CRC value isn't read from the user because the sysfs directory
         * doesn't include it and most messages from the bus search don't
         * print it either.  It would be unreasonable for the user to then
         * provide it.
         */
        const char *error_msg = "bad slave string format, expecting "
                "ff-dddddddddddd\n";

        if (buf[2] != '-') {
                dev_err(dev, "%s", error_msg);
                return -EINVAL;
        }
        i = sscanf(buf, "%02x-%012llx", &family, &id);
        if (i != 2) {
                dev_err(dev, "%s", error_msg);
                return -EINVAL;
        }
        rn->family = family;
        rn->id = id;

        rn64_le = cpu_to_le64(*(u64 *)rn);
        rn->crc = w1_calc_crc8((u8 *)&rn64_le, 7);

#if 0
        dev_info(dev, "With CRC device is %02x.%012llx.%02x.\n",
                  rn->family, (unsigned long long)rn->id, rn->crc);
#endif

        return 0;
}

/* Searches the slaves in the w1_master and returns a pointer or NULL.
 * Note: must not hold list_mutex
 */
struct w1_slave *w1_slave_search_device(struct w1_master *dev,
        struct w1_reg_num *rn)
{
        struct w1_slave *sl;
        mutex_lock(&dev->list_mutex);
        list_for_each_entry(sl, &dev->slist, w1_slave_entry) {
                if (sl->reg_num.family == rn->family &&
                                sl->reg_num.id == rn->id &&
                                sl->reg_num.crc == rn->crc) {
                        mutex_unlock(&dev->list_mutex);
                        return sl;
                }
        }
        mutex_unlock(&dev->list_mutex);
        return NULL;
}

static ssize_t w1_master_attribute_store_add(struct device *dev,
                                                struct device_attribute *attr,
                                                const char *buf, size_t count)
{
        struct w1_master *md = dev_to_w1_master(dev);
        struct w1_reg_num rn;
        struct w1_slave *sl;
        ssize_t result = count;

        if (w1_atoreg_num(dev, buf, count, &rn))
                return -EINVAL;

        mutex_lock(&md->mutex);
        sl = w1_slave_search_device(md, &rn);
        /* It would be nice to do a targeted search one the one-wire bus
         * for the new device to see if it is out there or not.  But the
         * current search doesn't support that.
         */
        if (sl) {
                dev_info(dev, "Device %s already exists\n", sl->name);
                result = -EINVAL;
        } else {
                w1_attach_slave_device(md, &rn);
        }
        mutex_unlock(&md->mutex);

        return result;
}

static ssize_t w1_master_attribute_show_remove(struct device *dev,
        struct device_attribute *attr, char *buf)
{
        int c = PAGE_SIZE;
        c -= snprintf(buf+PAGE_SIZE - c, c,
                "write device id xx-xxxxxxxxxxxx to remove slave\n");
        return PAGE_SIZE - c;
}

static ssize_t w1_master_attribute_store_remove(struct device *dev,
                                                struct device_attribute *attr,
                                                const char *buf, size_t count)
{
        struct w1_master *md = dev_to_w1_master(dev);
        struct w1_reg_num rn;
        struct w1_slave *sl;
        ssize_t result;

        if (w1_atoreg_num(dev, buf, count, &rn))
                return -EINVAL;

        mutex_lock(&md->mutex);
        sl = w1_slave_search_device(md, &rn);
        if (sl) {
                result = w1_slave_detach(sl);
                /* refcnt 0 means it was detached in the call */
                if (result == 0)
                        result = count;
        } else {
                dev_info(dev, "Device %02x-%012llx doesn't exist\n", rn.family,
                        (unsigned long long)rn.id);
                result = -EINVAL;
        }
        mutex_unlock(&md->mutex);

        return result;
}

#define W1_MASTER_ATTR_RO(_name, _mode)                         \
        struct device_attribute w1_master_attribute_##_name =   \
                __ATTR(w1_master_##_name, _mode,                \
                       w1_master_attribute_show_##_name, NULL)

#define W1_MASTER_ATTR_RW(_name, _mode)                         \
        struct device_attribute w1_master_attribute_##_name =   \
                __ATTR(w1_master_##_name, _mode,                \
                       w1_master_attribute_show_##_name,        \
                       w1_master_attribute_store_##_name)

static W1_MASTER_ATTR_RO(name, S_IRUGO);
static W1_MASTER_ATTR_RO(slaves, S_IRUGO);
static W1_MASTER_ATTR_RO(slave_count, S_IRUGO);
static W1_MASTER_ATTR_RW(max_slave_count, S_IRUGO | S_IWUSR | S_IWGRP);
static W1_MASTER_ATTR_RO(attempts, S_IRUGO);
static W1_MASTER_ATTR_RO(timeout, S_IRUGO);
static W1_MASTER_ATTR_RO(timeout_us, S_IRUGO);
static W1_MASTER_ATTR_RO(pointer, S_IRUGO);
static W1_MASTER_ATTR_RW(search, S_IRUGO | S_IWUSR | S_IWGRP);
static W1_MASTER_ATTR_RW(pullup, S_IRUGO | S_IWUSR | S_IWGRP);
static W1_MASTER_ATTR_RW(add, S_IRUGO | S_IWUSR | S_IWGRP);
static W1_MASTER_ATTR_RW(remove, S_IRUGO | S_IWUSR | S_IWGRP);

static struct attribute *w1_master_default_attrs[] = {
        &w1_master_attribute_name.attr,
        &w1_master_attribute_slaves.attr,
        &w1_master_attribute_slave_count.attr,
        &w1_master_attribute_max_slave_count.attr,
        &w1_master_attribute_attempts.attr,
        &w1_master_attribute_timeout.attr,
        &w1_master_attribute_timeout_us.attr,
        &w1_master_attribute_pointer.attr,
        &w1_master_attribute_search.attr,
        &w1_master_attribute_pullup.attr,
        &w1_master_attribute_add.attr,
        &w1_master_attribute_remove.attr,
        NULL
};

static const struct attribute_group w1_master_defattr_group = {
        .attrs = w1_master_default_attrs,
};

int w1_create_master_attributes(struct w1_master *master)
{
        return sysfs_create_group(&master->dev.kobj, &w1_master_defattr_group);
}

void w1_destroy_master_attributes(struct w1_master *master)
{
        sysfs_remove_group(&master->dev.kobj, &w1_master_defattr_group);
}

static int w1_uevent(const struct device *dev, struct kobj_uevent_env *env)
{
        const struct w1_master *md = NULL;
        const struct w1_slave *sl = NULL;
        const char *event_owner, *name;
        int err = 0;

        if (dev->driver == &w1_master_driver) {
                md = container_of(dev, struct w1_master, dev);
                event_owner = "master";
                name = md->name;
        } else if (dev->driver == &w1_slave_driver) {
                sl = container_of(dev, struct w1_slave, dev);
                event_owner = "slave";
                name = sl->name;
        } else {
                dev_dbg(dev, "Unknown event.\n");
                return -EINVAL;
        }

        dev_dbg(dev, "Hotplug event for %s %s, bus_id=%s.\n",
                        event_owner, name, dev_name(dev));

        if (dev->driver != &w1_slave_driver || !sl)
                goto end;

        err = add_uevent_var(env, "W1_FID=%02X", sl->reg_num.family);
        if (err)
                goto end;

        err = add_uevent_var(env, "W1_SLAVE_ID=%024LX",
                             (unsigned long long)sl->reg_num.id);
end:
        return err;
}

static int w1_family_notify(unsigned long action, struct w1_slave *sl)
{
        const struct w1_family_ops *fops;
        int err;

        fops = sl->family->fops;

        if (!fops)
                return 0;

        switch (action) {
        case BUS_NOTIFY_ADD_DEVICE:
                /* if the family driver needs to initialize something... */
                if (fops->add_slave) {
                        err = fops->add_slave(sl);
                        if (err < 0) {
                                dev_err(&sl->dev,
                                        "add_slave() call failed. err=%d\n",
                                        err);
                                return err;
                        }
                }
                if (fops->groups) {
                        err = sysfs_create_groups(&sl->dev.kobj, fops->groups);
                        if (err) {
                                dev_err(&sl->dev,
                                        "sysfs group creation failed. err=%d\n",
                                        err);
                                return err;
                        }
                }
                if (IS_REACHABLE(CONFIG_HWMON) && fops->chip_info) {
                        struct device *hwmon
                                = hwmon_device_register_with_info(&sl->dev,
                                                "w1_slave_temp", sl,
                                                fops->chip_info,
                                                NULL);
                        if (IS_ERR(hwmon)) {
                                dev_warn(&sl->dev,
                                         "could not create hwmon device\n");
                        } else {
                                sl->hwmon = hwmon;
                        }
                }
                break;
        case BUS_NOTIFY_DEL_DEVICE:
                if (IS_REACHABLE(CONFIG_HWMON) && fops->chip_info &&
                            sl->hwmon)
                        hwmon_device_unregister(sl->hwmon);
                if (fops->remove_slave)
                        sl->family->fops->remove_slave(sl);
                if (fops->groups)
                        sysfs_remove_groups(&sl->dev.kobj, fops->groups);
                break;
        }
        return 0;
}

static int __w1_attach_slave_device(struct w1_slave *sl)
{
        int err;

        sl->dev.parent = &sl->master->dev;
        sl->dev.driver = &w1_slave_driver;
        sl->dev.bus = &w1_bus_type;
        sl->dev.release = &w1_slave_release;
        sl->dev.groups = w1_slave_groups;
        sl->dev.of_node = of_find_matching_node(sl->master->dev.of_node,
                                                sl->family->of_match_table);

        dev_set_name(&sl->dev, "%02x-%012llx",
                 (unsigned int) sl->reg_num.family,
                 (unsigned long long) sl->reg_num.id);
        snprintf(&sl->name[0], sizeof(sl->name),
                 "%02x-%012llx",
                 (unsigned int) sl->reg_num.family,
                 (unsigned long long) sl->reg_num.id);

        dev_dbg(&sl->dev, "%s: registering %s as %p.\n", __func__,
                dev_name(&sl->dev), sl);

        /* suppress for w1_family_notify before sending KOBJ_ADD */
        dev_set_uevent_suppress(&sl->dev, true);

        err = device_register(&sl->dev);
        if (err < 0) {
                dev_err(&sl->dev,
                        "Device registration [%s] failed. err=%d\n",
                        dev_name(&sl->dev), err);
                of_node_put(sl->dev.of_node);
                put_device(&sl->dev);
                return err;
        }
        w1_family_notify(BUS_NOTIFY_ADD_DEVICE, sl);

        dev_set_uevent_suppress(&sl->dev, false);
        kobject_uevent(&sl->dev.kobj, KOBJ_ADD);

        mutex_lock(&sl->master->list_mutex);
        list_add_tail(&sl->w1_slave_entry, &sl->master->slist);
        mutex_unlock(&sl->master->list_mutex);

        return 0;
}

int w1_attach_slave_device(struct w1_master *dev, struct w1_reg_num *rn)
{
        struct w1_slave *sl;
        struct w1_family *f;
        int err;
        struct w1_netlink_msg msg;

        sl = kzalloc(sizeof(struct w1_slave), GFP_KERNEL);
        if (!sl) {
                dev_err(&dev->dev,
                         "%s: failed to allocate new slave device.\n",
                         __func__);
                return -ENOMEM;
        }


        sl->owner = THIS_MODULE;
        sl->master = dev;
        set_bit(W1_SLAVE_ACTIVE, &sl->flags);

        memset(&msg, 0, sizeof(msg));
        memcpy(&sl->reg_num, rn, sizeof(sl->reg_num));
        atomic_set(&sl->refcnt, 1);
        atomic_inc(&sl->master->refcnt);
        dev->slave_count++;
        dev_info(&dev->dev, "Attaching one wire slave %02x.%012llx crc %02x\n",
                  rn->family, (unsigned long long)rn->id, rn->crc);

        /* slave modules need to be loaded in a context with unlocked mutex */
        mutex_unlock(&dev->mutex);
        request_module("w1-family-0x%02X", rn->family);
        mutex_lock(&dev->mutex);

        spin_lock(&w1_flock);
        f = w1_family_registered(rn->family);
        if (!f) {
                f= &w1_default_family;
                dev_info(&dev->dev, "Family %x for %02x.%012llx.%02x is not registered.\n",
                          rn->family, rn->family,
                          (unsigned long long)rn->id, rn->crc);
        }
        __w1_family_get(f);
        spin_unlock(&w1_flock);

        sl->family = f;

        err = __w1_attach_slave_device(sl);
        if (err < 0) {
                dev_err(&dev->dev, "%s: Attaching %s failed.\n", __func__,
                         sl->name);
                dev->slave_count--;
                w1_family_put(sl->family);
                atomic_dec(&sl->master->refcnt);
                kfree(sl);
                return err;
        }

        sl->ttl = dev->slave_ttl;

        memcpy(msg.id.id, rn, sizeof(msg.id));
        msg.type = W1_SLAVE_ADD;
        w1_netlink_send(dev, &msg);

        return 0;
}

int w1_unref_slave(struct w1_slave *sl)
{
        struct w1_master *dev = sl->master;
        int refcnt;
        mutex_lock(&dev->list_mutex);
        refcnt = atomic_sub_return(1, &sl->refcnt);
        if (refcnt == 0) {
                struct w1_netlink_msg msg;

                dev_dbg(&sl->dev, "%s: detaching %s [%p].\n", __func__,
                        sl->name, sl);

                list_del(&sl->w1_slave_entry);

                memset(&msg, 0, sizeof(msg));
                memcpy(msg.id.id, &sl->reg_num, sizeof(msg.id));
                msg.type = W1_SLAVE_REMOVE;
                w1_netlink_send(sl->master, &msg);

                w1_family_notify(BUS_NOTIFY_DEL_DEVICE, sl);
                device_unregister(&sl->dev);
                #ifdef DEBUG
                memset(sl, 0, sizeof(*sl));
                #endif
                kfree(sl);
        }
        atomic_dec(&dev->refcnt);
        mutex_unlock(&dev->list_mutex);
        return refcnt;
}

int w1_slave_detach(struct w1_slave *sl)
{
        /* Only detach a slave once as it decreases the refcnt each time. */
        int destroy_now;
        mutex_lock(&sl->master->list_mutex);
        destroy_now = !test_bit(W1_SLAVE_DETACH, &sl->flags);
        set_bit(W1_SLAVE_DETACH, &sl->flags);
        mutex_unlock(&sl->master->list_mutex);

        if (destroy_now)
                destroy_now = !w1_unref_slave(sl);
        return destroy_now ? 0 : -EBUSY;
}

struct w1_master *w1_search_master_id(u32 id)
{
        struct w1_master *dev = NULL, *iter;

        mutex_lock(&w1_mlock);
        list_for_each_entry(iter, &w1_masters, w1_master_entry) {
                if (iter->id == id) {
                        dev = iter;
                        atomic_inc(&iter->refcnt);
                        break;
                }
        }
        mutex_unlock(&w1_mlock);

        return dev;
}

struct w1_slave *w1_search_slave(struct w1_reg_num *id)
{
        struct w1_master *dev;
        struct w1_slave *sl = NULL, *iter;

        mutex_lock(&w1_mlock);
        list_for_each_entry(dev, &w1_masters, w1_master_entry) {
                mutex_lock(&dev->list_mutex);
                list_for_each_entry(iter, &dev->slist, w1_slave_entry) {
                        if (iter->reg_num.family == id->family &&
                            iter->reg_num.id == id->id &&
                            iter->reg_num.crc == id->crc) {
                                sl = iter;
                                atomic_inc(&dev->refcnt);
                                atomic_inc(&iter->refcnt);
                                break;
                        }
                }
                mutex_unlock(&dev->list_mutex);

                if (sl)
                        break;
        }
        mutex_unlock(&w1_mlock);

        return sl;
}

void w1_reconnect_slaves(struct w1_family *f, int attach)
{
        struct w1_slave *sl, *sln;
        struct w1_master *dev;

        mutex_lock(&w1_mlock);
        list_for_each_entry(dev, &w1_masters, w1_master_entry) {
                dev_dbg(&dev->dev, "Reconnecting slaves in device %s "
                        "for family %02x.\n", dev->name, f->fid);
                mutex_lock(&dev->mutex);
                mutex_lock(&dev->list_mutex);
                list_for_each_entry_safe(sl, sln, &dev->slist, w1_slave_entry) {
                        /* If it is a new family, slaves with the default
                         * family driver and are that family will be
                         * connected.  If the family is going away, devices
                         * matching that family are reconneced.
                         */
                        if ((attach && sl->family->fid == W1_FAMILY_DEFAULT
                                && sl->reg_num.family == f->fid) ||
                                (!attach && sl->family->fid == f->fid)) {
                                struct w1_reg_num rn;

                                mutex_unlock(&dev->list_mutex);
                                memcpy(&rn, &sl->reg_num, sizeof(rn));
                                /* If it was already in use let the automatic
                                 * scan pick it up again later.
                                 */
                                if (!w1_slave_detach(sl))
                                        w1_attach_slave_device(dev, &rn);
                                mutex_lock(&dev->list_mutex);
                        }
                }
                dev_dbg(&dev->dev, "Reconnecting slaves in device %s "
                        "has been finished.\n", dev->name);
                mutex_unlock(&dev->list_mutex);
                mutex_unlock(&dev->mutex);
        }
        mutex_unlock(&w1_mlock);
}

static int w1_addr_crc_is_valid(struct w1_master *dev, u64 rn)
{
        u64 rn_le = cpu_to_le64(rn);
        struct w1_reg_num *tmp = (struct w1_reg_num *)&rn;
        u8 crc;

        crc = w1_calc_crc8((u8 *)&rn_le, 7);

        /* quirk:
         *   DS28E04 (1w eeprom) has strapping pins to change
         *   address, but will not update the crc. So normal rules
         *   for consistent w1 addresses are violated. We test
         *   with the 7 LSBs of the address forced high.
         *
         *   (char*)&rn_le = { family, addr_lsb, ..., addr_msb, crc }.
         */
        if (crc != tmp->crc && tmp->family == W1_FAMILY_DS28E04) {
                u64 corr_le = rn_le;

                ((u8 *)&corr_le)[1] |= 0x7f;
                crc = w1_calc_crc8((u8 *)&corr_le, 7);

                dev_info(&dev->dev, "DS28E04 crc workaround on %02x.%012llx.%02x\n",
                        tmp->family, (unsigned long long)tmp->id, tmp->crc);
        }

        if (crc != tmp->crc) {
                dev_dbg(&dev->dev, "w1 addr crc mismatch: %02x.%012llx.%02x != 0x%02x.\n",
                        tmp->family, (unsigned long long)tmp->id, tmp->crc, crc);
                return 0;
        }
        return 1;
}

void w1_slave_found(struct w1_master *dev, u64 rn)
{
        struct w1_slave *sl;
        struct w1_reg_num *tmp;

        atomic_inc(&dev->refcnt);

        tmp = (struct w1_reg_num *) &rn;

        sl = w1_slave_search_device(dev, tmp);
        if (sl) {
                set_bit(W1_SLAVE_ACTIVE, &sl->flags);
        } else {
                if (rn && w1_addr_crc_is_valid(dev, rn))
                        w1_attach_slave_device(dev, tmp);
        }

        atomic_dec(&dev->refcnt);
}

/**
 * w1_search() - Performs a ROM Search & registers any devices found.
 * @dev: The master device to search
 * @search_type: W1_SEARCH to search all devices, or W1_ALARM_SEARCH
 * to return only devices in the alarmed state
 * @cb: Function to call when a device is found
 *
 * The 1-wire search is a simple binary tree search.
 * For each bit of the address, we read two bits and write one bit.
 * The bit written will put to sleep all devies that don't match that bit.
 * When the two reads differ, the direction choice is obvious.
 * When both bits are 0, we must choose a path to take.
 * When we can scan all 64 bits without having to choose a path, we are done.
 *
 * See "Application note 187 1-wire search algorithm" at www.maxim-ic.com
 *
 */
void w1_search(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb)
{
        u64 last_rn, rn, tmp64;
        int i, slave_count = 0;
        int last_zero, last_device;
        int search_bit, desc_bit;
        u8  triplet_ret = 0;

        search_bit = 0;
        rn = dev->search_id;
        last_rn = 0;
        last_device = 0;
        last_zero = -1;

        desc_bit = 64;

        while ( !last_device && (slave_count++ < dev->max_slave_count) ) {
                last_rn = rn;
                rn = 0;

                /*
                 * Reset bus and all 1-wire device state machines
                 * so they can respond to our requests.
                 *
                 * Return 0 - device(s) present, 1 - no devices present.
                 */
                mutex_lock(&dev->bus_mutex);
                if (w1_reset_bus(dev)) {
                        mutex_unlock(&dev->bus_mutex);
                        dev_dbg(&dev->dev, "No devices present on the wire.\n");
                        break;
                }

                /* Do fast search on single slave bus */
                if (dev->max_slave_count == 1) {
                        int rv;
                        w1_write_8(dev, W1_READ_ROM);
                        rv = w1_read_block(dev, (u8 *)&rn, 8);
                        mutex_unlock(&dev->bus_mutex);

                        if (rv == 8 && rn)
                                cb(dev, rn);

                        break;
                }

                /* Start the search */
                w1_write_8(dev, search_type);
                for (i = 0; i < 64; ++i) {
                        /* Determine the direction/search bit */
                        if (i == desc_bit)
                                search_bit = 1;   /* took the 0 path last time, so take the 1 path */
                        else if (i > desc_bit)
                                search_bit = 0;   /* take the 0 path on the next branch */
                        else
                                search_bit = ((last_rn >> i) & 0x1);

                        /* Read two bits and write one bit */
                        triplet_ret = w1_triplet(dev, search_bit);

                        /* quit if no device responded */
                        if ( (triplet_ret & 0x03) == 0x03 )
                                break;

                        /* If both directions were valid, and we took the 0 path... */
                        if (triplet_ret == 0)
                                last_zero = i;

                        /* extract the direction taken & update the device number */
                        tmp64 = (triplet_ret >> 2);
                        rn |= (tmp64 << i);

                        if (test_bit(W1_ABORT_SEARCH, &dev->flags)) {
                                mutex_unlock(&dev->bus_mutex);
                                dev_dbg(&dev->dev, "Abort w1_search\n");
                                return;
                        }
                }
                mutex_unlock(&dev->bus_mutex);

                if ( (triplet_ret & 0x03) != 0x03 ) {
                        if ((desc_bit == last_zero) || (last_zero < 0)) {
                                last_device = 1;
                                dev->search_id = 0;
                        } else {
                                dev->search_id = rn;
                        }
                        desc_bit = last_zero;
                        cb(dev, rn);
                }

                if (!last_device && slave_count == dev->max_slave_count &&
                        !test_bit(W1_WARN_MAX_COUNT, &dev->flags)) {
                        /* Only max_slave_count will be scanned in a search,
                         * but it will start where it left off next search
                         * until all ids are identified and then it will start
                         * over.  A continued search will report the previous
                         * last id as the first id (provided it is still on the
                         * bus).
                         */
                        dev_info(&dev->dev, "%s: max_slave_count %d reached, "
                                "will continue next search.\n", __func__,
                                dev->max_slave_count);
                        set_bit(W1_WARN_MAX_COUNT, &dev->flags);
                }
        }
}

void w1_search_process_cb(struct w1_master *dev, u8 search_type,
        w1_slave_found_callback cb)
{
        struct w1_slave *sl, *sln;

        mutex_lock(&dev->list_mutex);
        list_for_each_entry(sl, &dev->slist, w1_slave_entry)
                clear_bit(W1_SLAVE_ACTIVE, &sl->flags);
        mutex_unlock(&dev->list_mutex);

        w1_search_devices(dev, search_type, cb);

        mutex_lock(&dev->list_mutex);
        list_for_each_entry_safe(sl, sln, &dev->slist, w1_slave_entry) {
                if (!test_bit(W1_SLAVE_ACTIVE, &sl->flags) && !--sl->ttl) {
                        mutex_unlock(&dev->list_mutex);
                        w1_slave_detach(sl);
                        mutex_lock(&dev->list_mutex);
                }
                else if (test_bit(W1_SLAVE_ACTIVE, &sl->flags))
                        sl->ttl = dev->slave_ttl;
        }
        mutex_unlock(&dev->list_mutex);

        if (dev->search_count > 0)
                dev->search_count--;
}

static void w1_search_process(struct w1_master *dev, u8 search_type)
{
        w1_search_process_cb(dev, search_type, w1_slave_found);
}

/**
 * w1_process_callbacks() - execute each dev->async_list callback entry
 * @dev: w1_master device
 *
 * The w1 master list_mutex must be held.
 *
 * Return: 1 if there were commands to executed 0 otherwise
 */
int w1_process_callbacks(struct w1_master *dev)
{
        int ret = 0;
        struct w1_async_cmd *async_cmd, *async_n;

        /* The list can be added to in another thread, loop until it is empty */
        while (!list_empty(&dev->async_list)) {
                list_for_each_entry_safe(async_cmd, async_n, &dev->async_list,
                        async_entry) {
                        /* drop the lock, if it is a search it can take a long
                         * time */
                        mutex_unlock(&dev->list_mutex);
                        async_cmd->cb(dev, async_cmd);
                        ret = 1;
                        mutex_lock(&dev->list_mutex);
                }
        }
        return ret;
}

int w1_process(void *data)
{
        struct w1_master *dev = (struct w1_master *) data;
        /* As long as w1_timeout is only set by a module parameter the sleep
         * time can be calculated in jiffies once.
         */
        const unsigned long jtime =
          usecs_to_jiffies(w1_timeout * 1000000 + w1_timeout_us);
        /* remainder if it woke up early */
        unsigned long jremain = 0;

        atomic_inc(&dev->refcnt);

        for (;;) {

                if (!jremain && dev->search_count) {
                        mutex_lock(&dev->mutex);
                        w1_search_process(dev, W1_SEARCH);
                        mutex_unlock(&dev->mutex);
                }

                mutex_lock(&dev->list_mutex);
                /* Note, w1_process_callback drops the lock while processing,
                 * but locks it again before returning.
                 */
                if (!w1_process_callbacks(dev) && jremain) {
                        /* a wake up is either to stop the thread, process
                         * callbacks, or search, it isn't process callbacks, so
                         * schedule a search.
                         */
                        jremain = 1;
                }

                __set_current_state(TASK_INTERRUPTIBLE);

                /* hold list_mutex until after interruptible to prevent loosing
                 * the wakeup signal when async_cmd is added.
                 */
                mutex_unlock(&dev->list_mutex);

                if (kthread_should_stop()) {
                        __set_current_state(TASK_RUNNING);
                        break;
                }

                /* Only sleep when the search is active. */
                if (dev->search_count) {
                        if (!jremain)
                                jremain = jtime;
                        jremain = schedule_timeout(jremain);
                }
                else
                        schedule();
        }

        atomic_dec(&dev->refcnt);

        return 0;
}

static int __init w1_init(void)
{
        int retval;

        pr_info("Driver for 1-wire Dallas network protocol.\n");

        w1_init_netlink();

        retval = bus_register(&w1_bus_type);
        if (retval) {
                pr_err("Failed to register bus. err=%d.\n", retval);
                goto err_out_exit_init;
        }

        retval = driver_register(&w1_master_driver);
        if (retval) {
                pr_err("Failed to register master driver. err=%d.\n",
                        retval);
                goto err_out_bus_unregister;
        }

        retval = driver_register(&w1_slave_driver);
        if (retval) {
                pr_err("Failed to register slave driver. err=%d.\n",
                        retval);
                goto err_out_master_unregister;
        }

        return 0;

#if 0
/* For undoing the slave register if there was a step after it. */
err_out_slave_unregister:
        driver_unregister(&w1_slave_driver);
#endif

err_out_master_unregister:
        driver_unregister(&w1_master_driver);

err_out_bus_unregister:
        bus_unregister(&w1_bus_type);

err_out_exit_init:
        return retval;
}

static void __exit w1_fini(void)
{
        struct w1_master *dev, *n;

        /* Set netlink removal messages and some cleanup */
        list_for_each_entry_safe(dev, n, &w1_masters, w1_master_entry)
                __w1_remove_master_device(dev);

        w1_fini_netlink();

        driver_unregister(&w1_slave_driver);
        driver_unregister(&w1_master_driver);
        bus_unregister(&w1_bus_type);
}

module_init(w1_init);
module_exit(w1_fini);

MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
MODULE_DESCRIPTION("Driver for 1-wire Dallas network protocol.");
MODULE_LICENSE("GPL");