fix memory hot remove not configured case.

[linux-2.6/sactl.git] / drivers / w1 / w1.c

/*
 *      w1.c
 *
 * Copyright (c) 2004 Evgeniy Polyakov <johnpol@2ka.mipt.ru>
 *
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#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 <asm/atomic.h>

#include "w1.h"
#include "w1_log.h"
#include "w1_int.h"
#include "w1_family.h"
#include "w1_netlink.h"

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Evgeniy Polyakov <johnpol@2ka.mipt.ru>");
MODULE_DESCRIPTION("Driver for 1-wire Dallas network protocol.");

static int w1_timeout = 10;
static int w1_control_timeout = 1;
int w1_max_slave_count = 10;
int w1_max_slave_ttl = 10;

module_param_named(timeout, w1_timeout, int, 0);
module_param_named(control_timeout, w1_control_timeout, int, 0);
module_param_named(max_slave_count, w1_max_slave_count, int, 0);
module_param_named(slave_ttl, w1_max_slave_ttl, int, 0);

DEFINE_MUTEX(w1_mlock);
LIST_HEAD(w1_masters);

static struct task_struct *w1_control_thread;

static int w1_master_match(struct device *dev, struct device_driver *drv)
{
        return 1;
}

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);

        printk("%s: Releasing %s.\n", __func__, sl->name);

        while (atomic_read(&sl->refcnt)) {
                printk("Waiting for %s to become free: refcnt=%d.\n",
                                sl->name, atomic_read(&sl->refcnt));
                if (msleep_interruptible(1000))
                        flush_signals(current);
        }

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

        complete(&sl->released);
}

static ssize_t w1_slave_read_name(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 ssize_t w1_slave_read_id(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);

        if (off > 8) {
                count = 0;
        } else {
                if (off + count > 8)
                        count = 8 - off;

                memcpy(buf, (u8 *)&sl->reg_num, count);
        }

        return count;
}

static struct device_attribute w1_slave_attr_name =
        __ATTR(name, S_IRUGO, w1_slave_read_name, NULL);

static struct bin_attribute w1_slave_attr_bin_id = {
      .attr = {
              .name = "id",
              .mode = S_IRUGO,
      },
      .size = 8,
      .read = w1_slave_read_id,
};

/* Default family */

static ssize_t w1_default_write(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 w1_default_read(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 struct bin_attribute w1_default_attr = {
      .attr = {
              .name = "rw",
              .mode = S_IRUGO | S_IWUSR,
      },
      .size = PAGE_SIZE,
      .read = w1_default_read,
      .write = w1_default_write,
};

static int w1_default_add_slave(struct w1_slave *sl)
{
        return sysfs_create_bin_file(&sl->dev.kobj, &w1_default_attr);
}

static void w1_default_remove_slave(struct w1_slave *sl)
{
        sysfs_remove_bin_file(&sl->dev.kobj, &w1_default_attr);
}

static struct w1_family_ops w1_default_fops = {
        .add_slave      = w1_default_add_slave,
        .remove_slave   = w1_default_remove_slave,
};

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

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

static struct bus_type w1_bus_type = {
        .name = "w1",
        .match = w1_master_match,
        .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,
        .bus_id = "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,
        .bus_id = "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)
{
        struct w1_master *md = dev_to_w1_master(dev);

        mutex_lock(&md->mutex);
        md->search_count = simple_strtol(buf, NULL, 0);
        mutex_unlock(&md->mutex);

        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_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)
{
        ssize_t count;
        count = sprintf(buf, "%d\n", w1_timeout);
        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;

        mutex_lock(&md->mutex);

        if (md->slave_count == 0)
                c -= snprintf(buf + PAGE_SIZE - c, c, "not found.\n");
        else {
                struct list_head *ent, *n;
                struct w1_slave *sl;

                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);
                }
        }

        mutex_unlock(&md->mutex);

        return PAGE_SIZE - c;
}

#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_RO(max_slave_count, S_IRUGO);
static W1_MASTER_ATTR_RO(attempts, S_IRUGO);
static W1_MASTER_ATTR_RO(timeout, S_IRUGO);
static W1_MASTER_ATTR_RO(pointer, S_IRUGO);
static W1_MASTER_ATTR_RW(search, S_IRUGO | S_IWUGO);

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_pointer.attr,
        &w1_master_attribute_search.attr,
        NULL
};

static 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);
}

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

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

        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->bus_id);

        if (dev->driver != &w1_slave_driver || !sl)
                return 0;

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

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

        return 0;
};
#else
static int w1_uevent(struct device *dev, struct kobj_uevent_env *env)
{
        return 0;
}
#endif

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;

        snprintf(&sl->dev.bus_id[0], sizeof(sl->dev.bus_id),
                 "%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__,
                &sl->dev.bus_id[0], sl);

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

        /* Create "name" entry */
        err = device_create_file(&sl->dev, &w1_slave_attr_name);
        if (err < 0) {
                dev_err(&sl->dev,
                        "sysfs file creation for [%s] failed. err=%d\n",
                        sl->dev.bus_id, err);
                goto out_unreg;
        }

        /* Create "id" entry */
        err = sysfs_create_bin_file(&sl->dev.kobj, &w1_slave_attr_bin_id);
        if (err < 0) {
                dev_err(&sl->dev,
                        "sysfs file creation for [%s] failed. err=%d\n",
                        sl->dev.bus_id, err);
                goto out_rem1;
        }

        /* if the family driver needs to initialize something... */
        if (sl->family->fops && sl->family->fops->add_slave &&
            ((err = sl->family->fops->add_slave(sl)) < 0)) {
                dev_err(&sl->dev,
                        "sysfs file creation for [%s] failed. err=%d\n",
                        sl->dev.bus_id, err);
                goto out_rem2;
        }

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

        return 0;

out_rem2:
        sysfs_remove_bin_file(&sl->dev.kobj, &w1_slave_attr_bin_id);
out_rem1:
        device_remove_file(&sl->dev, &w1_slave_attr_name);
out_unreg:
        device_unregister(&sl->dev);
        return err;
}

static 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, (long *)&sl->flags);

        memset(&msg, 0, sizeof(msg));
        memcpy(&sl->reg_num, rn, sizeof(sl->reg_num));
        atomic_set(&sl->refcnt, 0);
        init_completion(&sl->released);

        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);
                w1_family_put(sl->family);
                kfree(sl);
                return err;
        }

        sl->ttl = dev->slave_ttl;
        dev->slave_count++;

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

        return 0;
}

static void w1_slave_detach(struct w1_slave *sl)
{
        struct w1_netlink_msg msg;

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

        list_del(&sl->w1_slave_entry);

        if (sl->family->fops && sl->family->fops->remove_slave)
                sl->family->fops->remove_slave(sl);

        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);

        sysfs_remove_bin_file(&sl->dev.kobj, &w1_slave_attr_bin_id);
        device_remove_file(&sl->dev, &w1_slave_attr_name);
        device_unregister(&sl->dev);

        wait_for_completion(&sl->released);
        kfree(sl);
}

static struct w1_master *w1_search_master(void *data)
{
        struct w1_master *dev;
        int found = 0;

        mutex_lock(&w1_mlock);
        list_for_each_entry(dev, &w1_masters, w1_master_entry) {
                if (dev->bus_master->data == data) {
                        found = 1;
                        atomic_inc(&dev->refcnt);
                        break;
                }
        }
        mutex_unlock(&w1_mlock);

        return (found)?dev:NULL;
}

struct w1_master *w1_search_master_id(u32 id)
{
        struct w1_master *dev;
        int found = 0;

        mutex_lock(&w1_mlock);
        list_for_each_entry(dev, &w1_masters, w1_master_entry) {
                if (dev->id == id) {
                        found = 1;
                        atomic_inc(&dev->refcnt);
                        break;
                }
        }
        mutex_unlock(&w1_mlock);

        return (found)?dev:NULL;
}

struct w1_slave *w1_search_slave(struct w1_reg_num *id)
{
        struct w1_master *dev;
        struct w1_slave *sl = NULL;
        int found = 0;

        mutex_lock(&w1_mlock);
        list_for_each_entry(dev, &w1_masters, w1_master_entry) {
                mutex_lock(&dev->mutex);
                list_for_each_entry(sl, &dev->slist, w1_slave_entry) {
                        if (sl->reg_num.family == id->family &&
                                        sl->reg_num.id == id->id &&
                                        sl->reg_num.crc == id->crc) {
                                found = 1;
                                atomic_inc(&dev->refcnt);
                                atomic_inc(&sl->refcnt);
                                break;
                        }
                }
                mutex_unlock(&dev->mutex);

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

        return (found)?sl:NULL;
}

void w1_reconnect_slaves(struct w1_family *f)
{
        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 %s into new family %02x.\n",
                                dev->name, f->fid);
                set_bit(W1_MASTER_NEED_RECONNECT, &dev->flags);
        }
        mutex_unlock(&w1_mlock);
}

static void w1_slave_found(void *data, u64 rn)
{
        int slave_count;
        struct w1_slave *sl;
        struct list_head *ent;
        struct w1_reg_num *tmp;
        int family_found = 0;
        struct w1_master *dev;
        u64 rn_le = cpu_to_le64(rn);

        dev = w1_search_master(data);
        if (!dev) {
                printk(KERN_ERR "Failed to find w1 master device for data %p, "
                       "it is impossible.\n", data);
                return;
        }

        tmp = (struct w1_reg_num *) &rn;

        slave_count = 0;
        list_for_each(ent, &dev->slist) {

                sl = list_entry(ent, struct w1_slave, w1_slave_entry);

                if (sl->reg_num.family == tmp->family &&
                    sl->reg_num.id == tmp->id &&
                    sl->reg_num.crc == tmp->crc) {
                        set_bit(W1_SLAVE_ACTIVE, (long *)&sl->flags);
                        break;
                } else if (sl->reg_num.family == tmp->family) {
                        family_found = 1;
                        break;
                }

                slave_count++;
        }

        if (slave_count == dev->slave_count &&
                rn && ((rn >> 56) & 0xff) == w1_calc_crc8((u8 *)&rn_le, 7)) {
                w1_attach_slave_device(dev, tmp);
        }

        atomic_dec(&dev->refcnt);
}

/**
 * Performs a ROM Search & registers any devices 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
 *
 * @dev        The master device to search
 * @cb         Function to call when a device is found
 */
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 = 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.
                 */
                if (w1_reset_bus(dev)) {
                        dev_dbg(&dev->dev, "No devices present on the wire.\n");
                        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 ( (triplet_ret & 0x03) != 0x03 ) {
                        if ( (desc_bit == last_zero) || (last_zero < 0))
                                last_device = 1;
                        desc_bit = last_zero;
                        cb(dev->bus_master->data, rn);
                }
        }
}

static int w1_control(void *data)
{
        struct w1_slave *sl, *sln;
        struct w1_master *dev, *n;
        int have_to_wait = 0;

        set_freezable();
        while (!kthread_should_stop() || have_to_wait) {
                have_to_wait = 0;

                try_to_freeze();
                msleep_interruptible(w1_control_timeout * 1000);

                list_for_each_entry_safe(dev, n, &w1_masters, w1_master_entry) {
                        if (!kthread_should_stop() && !dev->flags)
                                continue;
                        /*
                         * Little race: we can create thread but not set the flag.
                         * Get a chance for external process to set flag up.
                         */
                        if (!dev->initialized) {
                                have_to_wait = 1;
                                continue;
                        }

                        if (kthread_should_stop() || test_bit(W1_MASTER_NEED_EXIT, &dev->flags)) {
                                set_bit(W1_MASTER_NEED_EXIT, &dev->flags);

                                mutex_lock(&w1_mlock);
                                list_del(&dev->w1_master_entry);
                                mutex_unlock(&w1_mlock);

                                mutex_lock(&dev->mutex);
                                list_for_each_entry_safe(sl, sln, &dev->slist, w1_slave_entry) {
                                        w1_slave_detach(sl);
                                }
                                w1_destroy_master_attributes(dev);
                                mutex_unlock(&dev->mutex);
                                atomic_dec(&dev->refcnt);
                                continue;
                        }

                        if (test_bit(W1_MASTER_NEED_RECONNECT, &dev->flags)) {
                                dev_dbg(&dev->dev, "Reconnecting slaves in device %s.\n", dev->name);
                                mutex_lock(&dev->mutex);
                                list_for_each_entry_safe(sl, sln, &dev->slist, w1_slave_entry) {
                                        if (sl->family->fid == W1_FAMILY_DEFAULT) {
                                                struct w1_reg_num rn;

                                                memcpy(&rn, &sl->reg_num, sizeof(rn));
                                                w1_slave_detach(sl);

                                                w1_attach_slave_device(dev, &rn);
                                        }
                                }
                                dev_dbg(&dev->dev, "Reconnecting slaves in device %s has been finished.\n", dev->name);
                                clear_bit(W1_MASTER_NEED_RECONNECT, &dev->flags);
                                mutex_unlock(&dev->mutex);
                        }
                }
        }

        return 0;
}

void w1_search_process(struct w1_master *dev, u8 search_type)
{
        struct w1_slave *sl, *sln;

        list_for_each_entry(sl, &dev->slist, w1_slave_entry)
                clear_bit(W1_SLAVE_ACTIVE, (long *)&sl->flags);

        w1_search_devices(dev, search_type, w1_slave_found);

        list_for_each_entry_safe(sl, sln, &dev->slist, w1_slave_entry) {
                if (!test_bit(W1_SLAVE_ACTIVE, (unsigned long *)&sl->flags) && !--sl->ttl) {
                        w1_slave_detach(sl);

                        dev->slave_count--;
                } else if (test_bit(W1_SLAVE_ACTIVE, (unsigned long *)&sl->flags))
                        sl->ttl = dev->slave_ttl;
        }

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

int w1_process(void *data)
{
        struct w1_master *dev = (struct w1_master *) data;

        while (!kthread_should_stop() && !test_bit(W1_MASTER_NEED_EXIT, &dev->flags)) {
                try_to_freeze();
                msleep_interruptible(w1_timeout * 1000);

                if (kthread_should_stop() || test_bit(W1_MASTER_NEED_EXIT, &dev->flags))
                        break;

                if (!dev->initialized)
                        continue;

                if (dev->search_count == 0)
                        continue;

                mutex_lock(&dev->mutex);
                w1_search_process(dev, W1_SEARCH);
                mutex_unlock(&dev->mutex);
        }

        atomic_dec(&dev->refcnt);

        return 0;
}

static int w1_init(void)
{
        int retval;

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

        w1_init_netlink();

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

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

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

        w1_control_thread = kthread_run(w1_control, NULL, "w1_control");
        if (IS_ERR(w1_control_thread)) {
                retval = PTR_ERR(w1_control_thread);
                printk(KERN_ERR "Failed to create control thread. err=%d\n",
                        retval);
                goto err_out_slave_unregister;
        }

        return 0;

err_out_slave_unregister:
        driver_unregister(&w1_slave_driver);

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 w1_fini(void)
{
        struct w1_master *dev;

        list_for_each_entry(dev, &w1_masters, w1_master_entry)
                __w1_remove_master_device(dev);

        w1_fini_netlink();

        kthread_stop(w1_control_thread);

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

module_init(w1_init);
module_exit(w1_fini);