treewide: remove redundant IS_ERR() before error code check

[linux/fpc-iii.git] / drivers / i2c / i2c-dev.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
    i2c-dev.c - i2c-bus driver, char device interface

    Copyright (C) 1995-97 Simon G. Vogl
    Copyright (C) 1998-99 Frodo Looijaard <frodol@dds.nl>
    Copyright (C) 2003 Greg Kroah-Hartman <greg@kroah.com>

*/

/* Note that this is a complete rewrite of Simon Vogl's i2c-dev module.
   But I have used so much of his original code and ideas that it seems
   only fair to recognize him as co-author -- Frodo */

/* The I2C_RDWR ioctl code is written by Kolja Waschk <waschk@telos.de> */

#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/i2c-dev.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/compat.h>

/*
 * An i2c_dev represents an i2c_adapter ... an I2C or SMBus master, not a
 * slave (i2c_client) with which messages will be exchanged.  It's coupled
 * with a character special file which is accessed by user mode drivers.
 *
 * The list of i2c_dev structures is parallel to the i2c_adapter lists
 * maintained by the driver model, and is updated using bus notifications.
 */
struct i2c_dev {
        struct list_head list;
        struct i2c_adapter *adap;
        struct device *dev;
        struct cdev cdev;
};

#define I2C_MINORS      (MINORMASK + 1)
static LIST_HEAD(i2c_dev_list);
static DEFINE_SPINLOCK(i2c_dev_list_lock);

static struct i2c_dev *i2c_dev_get_by_minor(unsigned index)
{
        struct i2c_dev *i2c_dev;

        spin_lock(&i2c_dev_list_lock);
        list_for_each_entry(i2c_dev, &i2c_dev_list, list) {
                if (i2c_dev->adap->nr == index)
                        goto found;
        }
        i2c_dev = NULL;
found:
        spin_unlock(&i2c_dev_list_lock);
        return i2c_dev;
}

static struct i2c_dev *get_free_i2c_dev(struct i2c_adapter *adap)
{
        struct i2c_dev *i2c_dev;

        if (adap->nr >= I2C_MINORS) {
                printk(KERN_ERR "i2c-dev: Out of device minors (%d)\n",
                       adap->nr);
                return ERR_PTR(-ENODEV);
        }

        i2c_dev = kzalloc(sizeof(*i2c_dev), GFP_KERNEL);
        if (!i2c_dev)
                return ERR_PTR(-ENOMEM);
        i2c_dev->adap = adap;

        spin_lock(&i2c_dev_list_lock);
        list_add_tail(&i2c_dev->list, &i2c_dev_list);
        spin_unlock(&i2c_dev_list_lock);
        return i2c_dev;
}

static void put_i2c_dev(struct i2c_dev *i2c_dev)
{
        spin_lock(&i2c_dev_list_lock);
        list_del(&i2c_dev->list);
        spin_unlock(&i2c_dev_list_lock);
        kfree(i2c_dev);
}

static ssize_t name_show(struct device *dev,
                         struct device_attribute *attr, char *buf)
{
        struct i2c_dev *i2c_dev = i2c_dev_get_by_minor(MINOR(dev->devt));

        if (!i2c_dev)
                return -ENODEV;
        return sprintf(buf, "%s\n", i2c_dev->adap->name);
}
static DEVICE_ATTR_RO(name);

static struct attribute *i2c_attrs[] = {
        &dev_attr_name.attr,
        NULL,
};
ATTRIBUTE_GROUPS(i2c);

/* ------------------------------------------------------------------------- */

/*
 * After opening an instance of this character special file, a file
 * descriptor starts out associated only with an i2c_adapter (and bus).
 *
 * Using the I2C_RDWR ioctl(), you can then *immediately* issue i2c_msg
 * traffic to any devices on the bus used by that adapter.  That's because
 * the i2c_msg vectors embed all the addressing information they need, and
 * are submitted directly to an i2c_adapter.  However, SMBus-only adapters
 * don't support that interface.
 *
 * To use read()/write() system calls on that file descriptor, or to use
 * SMBus interfaces (and work with SMBus-only hosts!), you must first issue
 * an I2C_SLAVE (or I2C_SLAVE_FORCE) ioctl.  That configures an anonymous
 * (never registered) i2c_client so it holds the addressing information
 * needed by those system calls and by this SMBus interface.
 */

static ssize_t i2cdev_read(struct file *file, char __user *buf, size_t count,
                loff_t *offset)
{
        char *tmp;
        int ret;

        struct i2c_client *client = file->private_data;

        if (count > 8192)
                count = 8192;

        tmp = kmalloc(count, GFP_KERNEL);
        if (tmp == NULL)
                return -ENOMEM;

        pr_debug("i2c-dev: i2c-%d reading %zu bytes.\n",
                iminor(file_inode(file)), count);

        ret = i2c_master_recv(client, tmp, count);
        if (ret >= 0)
                ret = copy_to_user(buf, tmp, count) ? -EFAULT : ret;
        kfree(tmp);
        return ret;
}

static ssize_t i2cdev_write(struct file *file, const char __user *buf,
                size_t count, loff_t *offset)
{
        int ret;
        char *tmp;
        struct i2c_client *client = file->private_data;

        if (count > 8192)
                count = 8192;

        tmp = memdup_user(buf, count);
        if (IS_ERR(tmp))
                return PTR_ERR(tmp);

        pr_debug("i2c-dev: i2c-%d writing %zu bytes.\n",
                iminor(file_inode(file)), count);

        ret = i2c_master_send(client, tmp, count);
        kfree(tmp);
        return ret;
}

static int i2cdev_check(struct device *dev, void *addrp)
{
        struct i2c_client *client = i2c_verify_client(dev);

        if (!client || client->addr != *(unsigned int *)addrp)
                return 0;

        return dev->driver ? -EBUSY : 0;
}

/* walk up mux tree */
static int i2cdev_check_mux_parents(struct i2c_adapter *adapter, int addr)
{
        struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
        int result;

        result = device_for_each_child(&adapter->dev, &addr, i2cdev_check);
        if (!result && parent)
                result = i2cdev_check_mux_parents(parent, addr);

        return result;
}

/* recurse down mux tree */
static int i2cdev_check_mux_children(struct device *dev, void *addrp)
{
        int result;

        if (dev->type == &i2c_adapter_type)
                result = device_for_each_child(dev, addrp,
                                                i2cdev_check_mux_children);
        else
                result = i2cdev_check(dev, addrp);

        return result;
}

/* This address checking function differs from the one in i2c-core
   in that it considers an address with a registered device, but no
   driver bound to it, as NOT busy. */
static int i2cdev_check_addr(struct i2c_adapter *adapter, unsigned int addr)
{
        struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
        int result = 0;

        if (parent)
                result = i2cdev_check_mux_parents(parent, addr);

        if (!result)
                result = device_for_each_child(&adapter->dev, &addr,
                                                i2cdev_check_mux_children);

        return result;
}

static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client,
                unsigned nmsgs, struct i2c_msg *msgs)
{
        u8 __user **data_ptrs;
        int i, res;

        data_ptrs = kmalloc_array(nmsgs, sizeof(u8 __user *), GFP_KERNEL);
        if (data_ptrs == NULL) {
                kfree(msgs);
                return -ENOMEM;
        }

        res = 0;
        for (i = 0; i < nmsgs; i++) {
                /* Limit the size of the message to a sane amount */
                if (msgs[i].len > 8192) {
                        res = -EINVAL;
                        break;
                }

                data_ptrs[i] = (u8 __user *)msgs[i].buf;
                msgs[i].buf = memdup_user(data_ptrs[i], msgs[i].len);
                if (IS_ERR(msgs[i].buf)) {
                        res = PTR_ERR(msgs[i].buf);
                        break;
                }
                /* memdup_user allocates with GFP_KERNEL, so DMA is ok */
                msgs[i].flags |= I2C_M_DMA_SAFE;

                /*
                 * If the message length is received from the slave (similar
                 * to SMBus block read), we must ensure that the buffer will
                 * be large enough to cope with a message length of
                 * I2C_SMBUS_BLOCK_MAX as this is the maximum underlying bus
                 * drivers allow. The first byte in the buffer must be
                 * pre-filled with the number of extra bytes, which must be
                 * at least one to hold the message length, but can be
                 * greater (for example to account for a checksum byte at
                 * the end of the message.)
                 */
                if (msgs[i].flags & I2C_M_RECV_LEN) {
                        if (!(msgs[i].flags & I2C_M_RD) ||
                            msgs[i].len < 1 || msgs[i].buf[0] < 1 ||
                            msgs[i].len < msgs[i].buf[0] +
                                             I2C_SMBUS_BLOCK_MAX) {
                                i++;
                                res = -EINVAL;
                                break;
                        }

                        msgs[i].len = msgs[i].buf[0];
                }
        }
        if (res < 0) {
                int j;
                for (j = 0; j < i; ++j)
                        kfree(msgs[j].buf);
                kfree(data_ptrs);
                kfree(msgs);
                return res;
        }

        res = i2c_transfer(client->adapter, msgs, nmsgs);
        while (i-- > 0) {
                if (res >= 0 && (msgs[i].flags & I2C_M_RD)) {
                        if (copy_to_user(data_ptrs[i], msgs[i].buf,
                                         msgs[i].len))
                                res = -EFAULT;
                }
                kfree(msgs[i].buf);
        }
        kfree(data_ptrs);
        kfree(msgs);
        return res;
}

static noinline int i2cdev_ioctl_smbus(struct i2c_client *client,
                u8 read_write, u8 command, u32 size,
                union i2c_smbus_data __user *data)
{
        union i2c_smbus_data temp = {};
        int datasize, res;

        if ((size != I2C_SMBUS_BYTE) &&
            (size != I2C_SMBUS_QUICK) &&
            (size != I2C_SMBUS_BYTE_DATA) &&
            (size != I2C_SMBUS_WORD_DATA) &&
            (size != I2C_SMBUS_PROC_CALL) &&
            (size != I2C_SMBUS_BLOCK_DATA) &&
            (size != I2C_SMBUS_I2C_BLOCK_BROKEN) &&
            (size != I2C_SMBUS_I2C_BLOCK_DATA) &&
            (size != I2C_SMBUS_BLOCK_PROC_CALL)) {
                dev_dbg(&client->adapter->dev,
                        "size out of range (%x) in ioctl I2C_SMBUS.\n",
                        size);
                return -EINVAL;
        }
        /* Note that I2C_SMBUS_READ and I2C_SMBUS_WRITE are 0 and 1,
           so the check is valid if size==I2C_SMBUS_QUICK too. */
        if ((read_write != I2C_SMBUS_READ) &&
            (read_write != I2C_SMBUS_WRITE)) {
                dev_dbg(&client->adapter->dev,
                        "read_write out of range (%x) in ioctl I2C_SMBUS.\n",
                        read_write);
                return -EINVAL;
        }

        /* Note that command values are always valid! */

        if ((size == I2C_SMBUS_QUICK) ||
            ((size == I2C_SMBUS_BYTE) &&
            (read_write == I2C_SMBUS_WRITE)))
                /* These are special: we do not use data */
                return i2c_smbus_xfer(client->adapter, client->addr,
                                      client->flags, read_write,
                                      command, size, NULL);

        if (data == NULL) {
                dev_dbg(&client->adapter->dev,
                        "data is NULL pointer in ioctl I2C_SMBUS.\n");
                return -EINVAL;
        }

        if ((size == I2C_SMBUS_BYTE_DATA) ||
            (size == I2C_SMBUS_BYTE))
                datasize = sizeof(data->byte);
        else if ((size == I2C_SMBUS_WORD_DATA) ||
                 (size == I2C_SMBUS_PROC_CALL))
                datasize = sizeof(data->word);
        else /* size == smbus block, i2c block, or block proc. call */
                datasize = sizeof(data->block);

        if ((size == I2C_SMBUS_PROC_CALL) ||
            (size == I2C_SMBUS_BLOCK_PROC_CALL) ||
            (size == I2C_SMBUS_I2C_BLOCK_DATA) ||
            (read_write == I2C_SMBUS_WRITE)) {
                if (copy_from_user(&temp, data, datasize))
                        return -EFAULT;
        }
        if (size == I2C_SMBUS_I2C_BLOCK_BROKEN) {
                /* Convert old I2C block commands to the new
                   convention. This preserves binary compatibility. */
                size = I2C_SMBUS_I2C_BLOCK_DATA;
                if (read_write == I2C_SMBUS_READ)
                        temp.block[0] = I2C_SMBUS_BLOCK_MAX;
        }
        res = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
              read_write, command, size, &temp);
        if (!res && ((size == I2C_SMBUS_PROC_CALL) ||
                     (size == I2C_SMBUS_BLOCK_PROC_CALL) ||
                     (read_write == I2C_SMBUS_READ))) {
                if (copy_to_user(data, &temp, datasize))
                        return -EFAULT;
        }
        return res;
}

static long i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        struct i2c_client *client = file->private_data;
        unsigned long funcs;

        dev_dbg(&client->adapter->dev, "ioctl, cmd=0x%02x, arg=0x%02lx\n",
                cmd, arg);

        switch (cmd) {
        case I2C_SLAVE:
        case I2C_SLAVE_FORCE:
                if ((arg > 0x3ff) ||
                    (((client->flags & I2C_M_TEN) == 0) && arg > 0x7f))
                        return -EINVAL;
                if (cmd == I2C_SLAVE && i2cdev_check_addr(client->adapter, arg))
                        return -EBUSY;
                /* REVISIT: address could become busy later */
                client->addr = arg;
                return 0;
        case I2C_TENBIT:
                if (arg)
                        client->flags |= I2C_M_TEN;
                else
                        client->flags &= ~I2C_M_TEN;
                return 0;
        case I2C_PEC:
                /*
                 * Setting the PEC flag here won't affect kernel drivers,
                 * which will be using the i2c_client node registered with
                 * the driver model core.  Likewise, when that client has
                 * the PEC flag already set, the i2c-dev driver won't see
                 * (or use) this setting.
                 */
                if (arg)
                        client->flags |= I2C_CLIENT_PEC;
                else
                        client->flags &= ~I2C_CLIENT_PEC;
                return 0;
        case I2C_FUNCS:
                funcs = i2c_get_functionality(client->adapter);
                return put_user(funcs, (unsigned long __user *)arg);

        case I2C_RDWR: {
                struct i2c_rdwr_ioctl_data rdwr_arg;
                struct i2c_msg *rdwr_pa;

                if (copy_from_user(&rdwr_arg,
                                   (struct i2c_rdwr_ioctl_data __user *)arg,
                                   sizeof(rdwr_arg)))
                        return -EFAULT;

                /* Put an arbitrary limit on the number of messages that can
                 * be sent at once */
                if (rdwr_arg.nmsgs > I2C_RDWR_IOCTL_MAX_MSGS)
                        return -EINVAL;

                rdwr_pa = memdup_user(rdwr_arg.msgs,
                                      rdwr_arg.nmsgs * sizeof(struct i2c_msg));
                if (IS_ERR(rdwr_pa))
                        return PTR_ERR(rdwr_pa);

                return i2cdev_ioctl_rdwr(client, rdwr_arg.nmsgs, rdwr_pa);
        }

        case I2C_SMBUS: {
                struct i2c_smbus_ioctl_data data_arg;
                if (copy_from_user(&data_arg,
                                   (struct i2c_smbus_ioctl_data __user *) arg,
                                   sizeof(struct i2c_smbus_ioctl_data)))
                        return -EFAULT;
                return i2cdev_ioctl_smbus(client, data_arg.read_write,
                                          data_arg.command,
                                          data_arg.size,
                                          data_arg.data);
        }
        case I2C_RETRIES:
                if (arg > INT_MAX)
                        return -EINVAL;

                client->adapter->retries = arg;
                break;
        case I2C_TIMEOUT:
                if (arg > INT_MAX)
                        return -EINVAL;

                /* For historical reasons, user-space sets the timeout
                 * value in units of 10 ms.
                 */
                client->adapter->timeout = msecs_to_jiffies(arg * 10);
                break;
        default:
                /* NOTE:  returning a fault code here could cause trouble
                 * in buggy userspace code.  Some old kernel bugs returned
                 * zero in this case, and userspace code might accidentally
                 * have depended on that bug.
                 */
                return -ENOTTY;
        }
        return 0;
}

#ifdef CONFIG_COMPAT

struct i2c_smbus_ioctl_data32 {
        u8 read_write;
        u8 command;
        u32 size;
        compat_caddr_t data; /* union i2c_smbus_data *data */
};

struct i2c_msg32 {
        u16 addr;
        u16 flags;
        u16 len;
        compat_caddr_t buf;
};

struct i2c_rdwr_ioctl_data32 {
        compat_caddr_t msgs; /* struct i2c_msg __user *msgs */
        u32 nmsgs;
};

static long compat_i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        struct i2c_client *client = file->private_data;
        unsigned long funcs;
        switch (cmd) {
        case I2C_FUNCS:
                funcs = i2c_get_functionality(client->adapter);
                return put_user(funcs, (compat_ulong_t __user *)arg);
        case I2C_RDWR: {
                struct i2c_rdwr_ioctl_data32 rdwr_arg;
                struct i2c_msg32 *p;
                struct i2c_msg *rdwr_pa;
                int i;

                if (copy_from_user(&rdwr_arg,
                                   (struct i2c_rdwr_ioctl_data32 __user *)arg,
                                   sizeof(rdwr_arg)))
                        return -EFAULT;

                if (rdwr_arg.nmsgs > I2C_RDWR_IOCTL_MAX_MSGS)
                        return -EINVAL;

                rdwr_pa = kmalloc_array(rdwr_arg.nmsgs, sizeof(struct i2c_msg),
                                      GFP_KERNEL);
                if (!rdwr_pa)
                        return -ENOMEM;

                p = compat_ptr(rdwr_arg.msgs);
                for (i = 0; i < rdwr_arg.nmsgs; i++) {
                        struct i2c_msg32 umsg;
                        if (copy_from_user(&umsg, p + i, sizeof(umsg))) {
                                kfree(rdwr_pa);
                                return -EFAULT;
                        }
                        rdwr_pa[i] = (struct i2c_msg) {
                                .addr = umsg.addr,
                                .flags = umsg.flags,
                                .len = umsg.len,
                                .buf = compat_ptr(umsg.buf)
                        };
                }

                return i2cdev_ioctl_rdwr(client, rdwr_arg.nmsgs, rdwr_pa);
        }
        case I2C_SMBUS: {
                struct i2c_smbus_ioctl_data32   data32;
                if (copy_from_user(&data32,
                                   (void __user *) arg,
                                   sizeof(data32)))
                        return -EFAULT;
                return i2cdev_ioctl_smbus(client, data32.read_write,
                                          data32.command,
                                          data32.size,
                                          compat_ptr(data32.data));
        }
        default:
                return i2cdev_ioctl(file, cmd, arg);
        }
}
#else
#define compat_i2cdev_ioctl NULL
#endif

static int i2cdev_open(struct inode *inode, struct file *file)
{
        unsigned int minor = iminor(inode);
        struct i2c_client *client;
        struct i2c_adapter *adap;

        adap = i2c_get_adapter(minor);
        if (!adap)
                return -ENODEV;

        /* This creates an anonymous i2c_client, which may later be
         * pointed to some address using I2C_SLAVE or I2C_SLAVE_FORCE.
         *
         * This client is ** NEVER REGISTERED ** with the driver model
         * or I2C core code!!  It just holds private copies of addressing
         * information and maybe a PEC flag.
         */
        client = kzalloc(sizeof(*client), GFP_KERNEL);
        if (!client) {
                i2c_put_adapter(adap);
                return -ENOMEM;
        }
        snprintf(client->name, I2C_NAME_SIZE, "i2c-dev %d", adap->nr);

        client->adapter = adap;
        file->private_data = client;

        return 0;
}

static int i2cdev_release(struct inode *inode, struct file *file)
{
        struct i2c_client *client = file->private_data;

        i2c_put_adapter(client->adapter);
        kfree(client);
        file->private_data = NULL;

        return 0;
}

static const struct file_operations i2cdev_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .read           = i2cdev_read,
        .write          = i2cdev_write,
        .unlocked_ioctl = i2cdev_ioctl,
        .compat_ioctl   = compat_i2cdev_ioctl,
        .open           = i2cdev_open,
        .release        = i2cdev_release,
};

/* ------------------------------------------------------------------------- */

static struct class *i2c_dev_class;

static int i2cdev_attach_adapter(struct device *dev, void *dummy)
{
        struct i2c_adapter *adap;
        struct i2c_dev *i2c_dev;
        int res;

        if (dev->type != &i2c_adapter_type)
                return 0;
        adap = to_i2c_adapter(dev);

        i2c_dev = get_free_i2c_dev(adap);
        if (IS_ERR(i2c_dev))
                return PTR_ERR(i2c_dev);

        cdev_init(&i2c_dev->cdev, &i2cdev_fops);
        i2c_dev->cdev.owner = THIS_MODULE;
        res = cdev_add(&i2c_dev->cdev, MKDEV(I2C_MAJOR, adap->nr), 1);
        if (res)
                goto error_cdev;

        /* register this i2c device with the driver core */
        i2c_dev->dev = device_create(i2c_dev_class, &adap->dev,
                                     MKDEV(I2C_MAJOR, adap->nr), NULL,
                                     "i2c-%d", adap->nr);
        if (IS_ERR(i2c_dev->dev)) {
                res = PTR_ERR(i2c_dev->dev);
                goto error;
        }

        pr_debug("i2c-dev: adapter [%s] registered as minor %d\n",
                 adap->name, adap->nr);
        return 0;
error:
        cdev_del(&i2c_dev->cdev);
error_cdev:
        put_i2c_dev(i2c_dev);
        return res;
}

static int i2cdev_detach_adapter(struct device *dev, void *dummy)
{
        struct i2c_adapter *adap;
        struct i2c_dev *i2c_dev;

        if (dev->type != &i2c_adapter_type)
                return 0;
        adap = to_i2c_adapter(dev);

        i2c_dev = i2c_dev_get_by_minor(adap->nr);
        if (!i2c_dev) /* attach_adapter must have failed */
                return 0;

        cdev_del(&i2c_dev->cdev);
        put_i2c_dev(i2c_dev);
        device_destroy(i2c_dev_class, MKDEV(I2C_MAJOR, adap->nr));

        pr_debug("i2c-dev: adapter [%s] unregistered\n", adap->name);
        return 0;
}

static int i2cdev_notifier_call(struct notifier_block *nb, unsigned long action,
                         void *data)
{
        struct device *dev = data;

        switch (action) {
        case BUS_NOTIFY_ADD_DEVICE:
                return i2cdev_attach_adapter(dev, NULL);
        case BUS_NOTIFY_DEL_DEVICE:
                return i2cdev_detach_adapter(dev, NULL);
        }

        return 0;
}

static struct notifier_block i2cdev_notifier = {
        .notifier_call = i2cdev_notifier_call,
};

/* ------------------------------------------------------------------------- */

/*
 * module load/unload record keeping
 */

static int __init i2c_dev_init(void)
{
        int res;

        printk(KERN_INFO "i2c /dev entries driver\n");

        res = register_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS, "i2c");
        if (res)
                goto out;

        i2c_dev_class = class_create(THIS_MODULE, "i2c-dev");
        if (IS_ERR(i2c_dev_class)) {
                res = PTR_ERR(i2c_dev_class);
                goto out_unreg_chrdev;
        }
        i2c_dev_class->dev_groups = i2c_groups;

        /* Keep track of adapters which will be added or removed later */
        res = bus_register_notifier(&i2c_bus_type, &i2cdev_notifier);
        if (res)
                goto out_unreg_class;

        /* Bind to already existing adapters right away */
        i2c_for_each_dev(NULL, i2cdev_attach_adapter);

        return 0;

out_unreg_class:
        class_destroy(i2c_dev_class);
out_unreg_chrdev:
        unregister_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS);
out:
        printk(KERN_ERR "%s: Driver Initialisation failed\n", __FILE__);
        return res;
}

static void __exit i2c_dev_exit(void)
{
        bus_unregister_notifier(&i2c_bus_type, &i2cdev_notifier);
        i2c_for_each_dev(NULL, i2cdev_detach_adapter);
        class_destroy(i2c_dev_class);
        unregister_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS);
}

MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl> and "
                "Simon G. Vogl <simon@tk.uni-linz.ac.at>");
MODULE_DESCRIPTION("I2C /dev entries driver");
MODULE_LICENSE("GPL");

module_init(i2c_dev_init);
module_exit(i2c_dev_exit);