i2c-dev.c

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/*
    i2c-dev.c - i2c-bus driver, char device interface

    Copyright (C) 1995-97 Simon G. Vogl
    Copyright (C) 1998-99 Frodo Looijaard <[email protected]>
    Copyright (C) 2003 Greg Kroah-Hartman <[email protected]>

    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., 51 Franklin Street, Fifth Floor, Boston,
    MA 02110-1301 USA.
*/

/* 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 <[email protected]> */

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

#define I2C_MINORS  256
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 return_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 show_adapter_name(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(name, S_IRUGO, show_adapter_name, NULL);

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

/*
 * 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->f_path.dentry->d_inode), 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->f_path.dentry->d_inode), 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_rdrw(struct i2c_client *client,
        unsigned long arg)
{
    struct i2c_rdwr_ioctl_data rdwr_arg;
    struct i2c_msg *rdwr_pa;
    u8 __user **data_ptrs;
    int i, res;

    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_RDRW_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);

    data_ptrs = kmalloc(rdwr_arg.nmsgs * sizeof(u8 __user *), GFP_KERNEL);
    if (data_ptrs == NULL) {
        kfree(rdwr_pa);
        return -ENOMEM;
    }

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

        data_ptrs[i] = (u8 __user *)rdwr_pa[i].buf;
        rdwr_pa[i].buf = memdup_user(data_ptrs[i], rdwr_pa[i].len);
        if (IS_ERR(rdwr_pa[i].buf)) {
            res = PTR_ERR(rdwr_pa[i].buf);
            break;
        }

        /*
         * 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 (rdwr_pa[i].flags & I2C_M_RECV_LEN) {
            if (!(rdwr_pa[i].flags & I2C_M_RD) ||
                rdwr_pa[i].buf[0] < 1 ||
                rdwr_pa[i].len < rdwr_pa[i].buf[0] +
                         I2C_SMBUS_BLOCK_MAX) {
                res = -EINVAL;
                break;
            }

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

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

static noinline int i2cdev_ioctl_smbus(struct i2c_client *client,
        unsigned long arg)
{
    struct i2c_smbus_ioctl_data data_arg;
    union i2c_smbus_data temp;
    int datasize, res;

    if (copy_from_user(&data_arg,
               (struct i2c_smbus_ioctl_data __user *) arg,
               sizeof(struct i2c_smbus_ioctl_data)))
        return -EFAULT;
    if ((data_arg.size != I2C_SMBUS_BYTE) &&
        (data_arg.size != I2C_SMBUS_QUICK) &&
        (data_arg.size != I2C_SMBUS_BYTE_DATA) &&
        (data_arg.size != I2C_SMBUS_WORD_DATA) &&
        (data_arg.size != I2C_SMBUS_PROC_CALL) &&
        (data_arg.size != I2C_SMBUS_BLOCK_DATA) &&
        (data_arg.size != I2C_SMBUS_I2C_BLOCK_BROKEN) &&
        (data_arg.size != I2C_SMBUS_I2C_BLOCK_DATA) &&
        (data_arg.size != I2C_SMBUS_BLOCK_PROC_CALL)) {
        dev_dbg(&client->adapter->dev,
            "size out of range (%x) in ioctl I2C_SMBUS.\n",
            data_arg.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 ((data_arg.read_write != I2C_SMBUS_READ) &&
        (data_arg.read_write != I2C_SMBUS_WRITE)) {
        dev_dbg(&client->adapter->dev,
            "read_write out of range (%x) in ioctl I2C_SMBUS.\n",
            data_arg.read_write);
        return -EINVAL;
    }

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

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

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

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

    if ((data_arg.size == I2C_SMBUS_PROC_CALL) ||
        (data_arg.size == I2C_SMBUS_BLOCK_PROC_CALL) ||
        (data_arg.size == I2C_SMBUS_I2C_BLOCK_DATA) ||
        (data_arg.read_write == I2C_SMBUS_WRITE)) {
        if (copy_from_user(&temp, data_arg.data, datasize))
            return -EFAULT;
    }
    if (data_arg.size == I2C_SMBUS_I2C_BLOCK_BROKEN) {
        /* Convert old I2C block commands to the new
           convention. This preserves binary compatibility. */
        data_arg.size = I2C_SMBUS_I2C_BLOCK_DATA;
        if (data_arg.read_write == I2C_SMBUS_READ)
            temp.block[0] = I2C_SMBUS_BLOCK_MAX;
    }
    res = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
          data_arg.read_write, data_arg.command, data_arg.size, &temp);
    if (!res && ((data_arg.size == I2C_SMBUS_PROC_CALL) ||
             (data_arg.size == I2C_SMBUS_BLOCK_PROC_CALL) ||
             (data_arg.read_write == I2C_SMBUS_READ))) {
        if (copy_to_user(data_arg.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:
        /* NOTE:  devices set up to work with "new style" drivers
         * can't use I2C_SLAVE, even when the device node is not
         * bound to a driver.  Only I2C_SLAVE_FORCE will work.
         *
         * 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 > 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:
        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:
        return i2cdev_ioctl_rdrw(client, arg);

    case I2C_SMBUS:
        return i2cdev_ioctl_smbus(client, arg);

    case I2C_RETRIES:
        client->adapter->retries = arg;
        break;
    case I2C_TIMEOUT:
        /* 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;
}

static int i2cdev_open(struct inode *inode, struct file *file)
{
    unsigned int minor = iminor(inode);
    struct i2c_client *client;
    struct i2c_adapter *adap;
    struct i2c_dev *i2c_dev;

    i2c_dev = i2c_dev_get_by_minor(minor);
    if (!i2c_dev)
        return -ENODEV;

    adap = i2c_get_adapter(i2c_dev->adap->nr);
    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,
    .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);

    /* 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;
    }
    res = device_create_file(i2c_dev->dev, &dev_attr_name);
    if (res)
        goto error_destroy;

    pr_debug("i2c-dev: adapter [%s] registered as minor %d\n",
         adap->name, adap->nr);
    return 0;
error_destroy:
    device_destroy(i2c_dev_class, MKDEV(I2C_MAJOR, adap->nr));
error:
    return_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;

    device_remove_file(i2c_dev->dev, &dev_attr_name);
    return_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(I2C_MAJOR, "i2c", &i2cdev_fops);
    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;
    }

    /* 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(I2C_MAJOR, "i2c");
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(I2C_MAJOR, "i2c");
}

MODULE_AUTHOR("Frodo Looijaard <[email protected]> and "
        "Simon G. Vogl <[email protected]>");
MODULE_DESCRIPTION("I2C /dev entries driver");
MODULE_LICENSE("GPL");

module_init(i2c_dev_init);
module_exit(i2c_dev_exit);