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i2c-dev.c

/*
    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>

    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., 675 Mass Ave, Cambridge, MA 02139, 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 <waschk@telos.de> */

#include <linux/kernel.h>
#include <linux/module.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 <asm/uaccess.h>

static struct i2c_driver i2cdev_driver;

/*
 * 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 notifications
 * delivered to the i2cdev_driver.
 */
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 = (struct i2c_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 %zd 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 = (struct i2c_client *)file->private_data;

      if (count > 8192)
            count = 8192;

      tmp = kmalloc(count,GFP_KERNEL);
      if (tmp==NULL)
            return -ENOMEM;
      if (copy_from_user(tmp,buf,count)) {
            kfree(tmp);
            return -EFAULT;
      }

      pr_debug("i2c-dev: i2c-%d writing %zd bytes.\n",
            iminor(file->f_path.dentry->d_inode), count);

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

/* This address checking function differs from the one in i2c-core
   in that it considers an address with a registered device, but no
   bound driver, as NOT busy. */
static int i2cdev_check_addr(struct i2c_adapter *adapter, unsigned int addr)
{
      struct list_head *item;
      struct i2c_client *client;
      int res = 0;

      mutex_lock(&adapter->clist_lock);
      list_for_each(item, &adapter->clients) {
            client = list_entry(item, struct i2c_client, list);
            if (client->addr == addr) {
                  if (client->driver)
                        res = -EBUSY;
                  break;
            }
      }
      mutex_unlock(&adapter->clist_lock);

      return res;
}

static int i2cdev_ioctl(struct inode *inode, struct file *file,
            unsigned int cmd, unsigned long arg)
{
      struct i2c_client *client = (struct i2c_client *)file->private_data;
      struct i2c_rdwr_ioctl_data rdwr_arg;
      struct i2c_smbus_ioctl_data data_arg;
      union i2c_smbus_data temp;
      struct i2c_msg *rdwr_pa;
      u8 __user **data_ptrs;
      int i,datasize,res;
      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:
            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 = (struct i2c_msg *)
                  kmalloc(rdwr_arg.nmsgs * sizeof(struct i2c_msg),
                  GFP_KERNEL);

            if (rdwr_pa == NULL) return -ENOMEM;

            if (copy_from_user(rdwr_pa, rdwr_arg.msgs,
                           rdwr_arg.nmsgs * sizeof(struct i2c_msg))) {
                  kfree(rdwr_pa);
                  return -EFAULT;
            }

            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;
                   * and don't let length change either. */
                  if ((rdwr_pa[i].len > 8192) ||
                      (rdwr_pa[i].flags & I2C_M_RECV_LEN)) {
                        res = -EINVAL;
                        break;
                  }
                  data_ptrs[i] = (u8 __user *)rdwr_pa[i].buf;
                  rdwr_pa[i].buf = kmalloc(rdwr_pa[i].len, GFP_KERNEL);
                  if(rdwr_pa[i].buf == NULL) {
                        res = -ENOMEM;
                        break;
                  }
                  if(copy_from_user(rdwr_pa[i].buf,
                        data_ptrs[i],
                        rdwr_pa[i].len)) {
                              ++i; /* Needs to be kfreed too */
                              res = -EFAULT;
                        break;
                  }
            }
            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;

      case I2C_SMBUS:
            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;
      case I2C_RETRIES:
            client->adapter->retries = arg;
            break;
      case I2C_TIMEOUT:
            client->adapter->timeout = arg;
            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->driver = &i2cdev_driver;

      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,
      .ioctl            = i2cdev_ioctl,
      .open       = i2cdev_open,
      .release    = i2cdev_release,
};

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

/*
 * The legacy "i2cdev_driver" is used primarily to get notifications when
 * I2C adapters are added or removed, so that each one gets an i2c_dev
 * and is thus made available to userspace driver code.
 */

static struct class *i2c_dev_class;

static int i2cdev_attach_adapter(struct i2c_adapter *adap)
{
      struct i2c_dev *i2c_dev;
      int res;

      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),
                             "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 i2c_adapter *adap)
{
      struct i2c_dev *i2c_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_detach_client(struct i2c_client *client)
{
      return 0;
}

static struct i2c_driver i2cdev_driver = {
      .driver = {
            .name = "dev_driver",
      },
      .id         = I2C_DRIVERID_I2CDEV,
      .attach_adapter   = i2cdev_attach_adapter,
      .detach_adapter   = i2cdev_detach_adapter,
      .detach_client    = i2cdev_detach_client,
};

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

/*
 * 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))
            goto out_unreg_chrdev;

      res = i2c_add_driver(&i2cdev_driver);
      if (res)
            goto out_unreg_class;

      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)
{
      i2c_del_driver(&i2cdev_driver);
      class_destroy(i2c_dev_class);
      unregister_chrdev(I2C_MAJOR,"i2c");
}

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);

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