/*
      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.
  */
  
  /* 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/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)
  ",
  		       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 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
  ", 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.
  ",
  		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.
  ",
  		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 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_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);
  
  	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.
  ",
  			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.
  ",
  			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.
  ");
  		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
  ",
  		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:
  		return i2cdev_ioctl_rdwr(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;
  	}
  
  	pr_debug("i2c-dev: adapter [%s] registered as minor %d
  ",
  		 adap->name, adap->nr);
  	return 0;
  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;
  
  	return_i2c_dev(i2c_dev);
  	device_destroy(i2c_dev_class, MKDEV(I2C_MAJOR, adap->nr));
  
  	pr_debug("i2c-dev: adapter [%s] unregistered
  ", 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
  ");
  
  	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;
  	}
  	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(I2C_MAJOR, "i2c");
  out:
  	printk(KERN_ERR "%s: Driver Initialisation failed
  ", __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 <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);