path: root/drivers/i2c/i2c-core.c

/* i2c-core.c - a device driver for the iic-bus interface		     */
/* ------------------------------------------------------------------------- */
/*   Copyright (C) 1995-99 Simon G. Vogl

    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.		     */
/* ------------------------------------------------------------------------- */

/* With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi>.
   All SMBus-related things are written by Frodo Looijaard <frodol@dds.nl>
   SMBus 2.0 support by Mark Studebaker <mdsxyz123@yahoo.com>                */

#include <linux/config.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/idr.h>
#include <linux/seq_file.h>
#include <asm/uaccess.h>


static LIST_HEAD(adapters);
static LIST_HEAD(drivers);
static DECLARE_MUTEX(core_lists);
static DEFINE_IDR(i2c_adapter_idr);

/* match always succeeds, as we want the probe() to tell if we really accept this match */
static int i2c_device_match(struct device *dev, struct device_driver *drv)
{
	return 1;
}

static int i2c_bus_suspend(struct device * dev, pm_message_t state)
{
	int rc = 0;

	if (dev->driver && dev->driver->suspend)
		rc = dev->driver->suspend(dev,state,0);
	return rc;
}

static int i2c_bus_resume(struct device * dev)
{
	int rc = 0;
	
	if (dev->driver && dev->driver->resume)
		rc = dev->driver->resume(dev,0);
	return rc;
}

static struct bus_type i2c_bus_type = {
	.name =		"i2c",
	.match =	i2c_device_match,
	.suspend =      i2c_bus_suspend,
	.resume =       i2c_bus_resume,
};

static int i2c_device_probe(struct device *dev)
{
	return -ENODEV;
}

static int i2c_device_remove(struct device *dev)
{
	return 0;
}

static void i2c_adapter_dev_release(struct device *dev)
{
	struct i2c_adapter *adap = dev_to_i2c_adapter(dev);
	complete(&adap->dev_released);
}

static struct device_driver i2c_adapter_driver = {
	.name =	"i2c_adapter",
	.bus = &i2c_bus_type,
	.probe = i2c_device_probe,
	.remove = i2c_device_remove,
};

static void i2c_adapter_class_dev_release(struct class_device *dev)
{
	struct i2c_adapter *adap = class_dev_to_i2c_adapter(dev);
	complete(&adap->class_dev_released);
}

static struct class i2c_adapter_class = {
	.name =		"i2c-adapter",
	.release =	&i2c_adapter_class_dev_release,
};

static ssize_t show_adapter_name(struct device *dev, char *buf)
{
	struct i2c_adapter *adap = dev_to_i2c_adapter(dev);
	return sprintf(buf, "%s\n", adap->name);
}
static DEVICE_ATTR(name, S_IRUGO, show_adapter_name, NULL);


static void i2c_client_release(struct device *dev)
{
	struct i2c_client *client = to_i2c_client(dev);
	complete(&client->released);
}

static ssize_t show_client_name(struct device *dev, char *buf)
{
	struct i2c_client *client = to_i2c_client(dev);
	return sprintf(buf, "%s\n", client->name);
}

/* 
 * We can't use the DEVICE_ATTR() macro here as we want the same filename for a
 * different type of a device.  So beware if the DEVICE_ATTR() macro ever
 * changes, this definition will also have to change.
 */
static struct device_attribute dev_attr_client_name = {
	.attr	= {.name = "name", .mode = S_IRUGO, .owner = THIS_MODULE },
	.show	= &show_client_name,
};


/* ---------------------------------------------------
 * registering functions 
 * --------------------------------------------------- 
 */

/* -----
 * i2c_add_adapter is called from within the algorithm layer,
 * when a new hw adapter registers. A new device is register to be
 * available for clients.
 */
int i2c_add_adapter(struct i2c_adapter *adap)
{
	int id, res = 0;
	struct list_head   *item;
	struct i2c_driver  *driver;

	down(&core_lists);

	if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0) {
		res = -ENOMEM;
		goto out_unlock;
	}

	res = idr_get_new(&i2c_adapter_idr, NULL, &id);
	if (res < 0) {
		if (res == -EAGAIN)
			res = -ENOMEM;
		goto out_unlock;
	}

	adap->nr =  id & MAX_ID_MASK;
	init_MUTEX(&adap->bus_lock);
	init_MUTEX(&adap->clist_lock);
	list_add_tail(&adap->list,&adapters);
	INIT_LIST_HEAD(&adap->clients);

	/* Add the adapter to the driver core.
	 * If the parent pointer is not set up,
	 * we add this adapter to the host bus.
	 */
	if (adap->dev.parent == NULL)
		adap->dev.parent = &platform_bus;
	sprintf(adap->dev.bus_id, "i2c-%d", adap->nr);
	adap->dev.driver = &i2c_adapter_driver;
	adap->dev.release = &i2c_adapter_dev_release;
	device_register(&adap->dev);
	device_create_file(&adap->dev, &dev_attr_name);

	/* Add this adapter to the i2c_adapter class */
	memset(&adap->class_dev, 0x00, sizeof(struct class_device));
	adap->class_dev.dev = &adap->dev;
	adap->class_dev.class = &i2c_adapter_class;
	strlcpy(adap->class_dev.class_id, adap->dev.bus_id, BUS_ID_SIZE);
	class_device_register(&adap->class_dev);

	/* inform drivers of new adapters */
	list_for_each(item,&drivers) {
		driver = list_entry(item, struct i2c_driver, list);
		if (driver->flags & I2C_DF_NOTIFY)
			/* We ignore the return code; if it fails, too bad */
			driver->attach_adapter(adap);
	}

	dev_dbg(&adap->dev, "registered as adapter #%d\n", adap->nr);

out_unlock:
	up(&core_lists);
	return res;
}


int i2c_del_adapter(struct i2c_adapter *adap)
{
	struct list_head  *item, *_n;
	struct i2c_adapter *adap_from_list;
	struct i2c_driver *driver;
	struct i2c_client *client;
	int res = 0;

	down(&core_lists);

	/* First make sure that this adapter was ever added */
	list_for_each_entry(adap_from_list, &adapters, list) {
		if (adap_from_list == adap)
			break;
	}
	if (adap_from_list != adap) {
		pr_debug("I2C: Attempting to delete an unregistered "
			 "adapter\n");
		res = -EINVAL;
		goto out_unlock;
	}

	list_for_each(item,&drivers) {
		driver = list_entry(item, struct i2c_driver, list);
		if (driver->detach_adapter)
			if ((res = driver->detach_adapter(adap))) {
				dev_warn(&adap->dev, "can't detach adapter "
					 "while detaching driver %s: driver not "
					 "detached!", driver->name);
				goto out_unlock;
			}
	}

	/* detach any active clients. This must be done first, because
	 * it can fail; in which case we give upp. */
	list_for_each_safe(item, _n, &adap->clients) {
		client = list_entry(item, struct i2c_client, list);

		/* detaching devices is unconditional of the set notify
		 * flag, as _all_ clients that reside on the adapter
		 * must be deleted, as this would cause invalid states.
		 */
		if ((res=client->driver->detach_client(client))) {
			dev_err(&adap->dev, "adapter not "
				"unregistered, because client at "
				"address %02x can't be detached. ",
				client->addr);
			goto out_unlock;
		}
	}

	/* clean up the sysfs representation */
	init_completion(&adap->dev_released);
	init_completion(&adap->class_dev_released);
	class_device_unregister(&adap->class_dev);
	device_remove_file(&adap->dev, &dev_attr_name);
	device_unregister(&adap->dev);
	list_del(&adap->list);

	/* wait for sysfs to drop all references */
	wait_for_completion(&adap->dev_released);
	wait_for_completion(&adap->class_dev_released);

	/* free dynamically allocated bus id */
	idr_remove(&i2c_adapter_idr, adap->nr);

	dev_dbg(&adap->dev, "adapter unregistered\n");

 out_unlock:
	up(&core_lists);
	return res;
}


/* -----
 * What follows is the "upwards" interface: commands for talking to clients,
 * which implement the functions to access the physical information of the
 * chips.
 */

int i2c_add_driver(struct i2c_driver *driver)
{
	struct list_head   *item;
	struct i2c_adapter *adapter;
	int res = 0;

	down(&core_lists);

	/* add the driver to the list of i2c drivers in the driver core */
	driver->driver.name = driver->name;
	driver->driver.bus = &i2c_bus_type;
	driver->driver.probe = i2c_device_probe;
	driver->driver.remove = i2c_device_remove;

	res = driver_register(&driver->driver);
	if (res)
		goto out_unlock;
	
	list_add_tail(&driver->list,&drivers);
	pr_debug("i2c-core: driver %s registered.\n", driver->name);

	/* now look for instances of driver on our adapters */
	if (driver->flags & I2C_DF_NOTIFY) {
		list_for_each(item,&adapters) {
			adapter = list_entry(item, struct i2c_adapter, list);
			driver->attach_adapter(adapter);
		}
	}

 out_unlock:
	up(&core_lists);
	return res;
}

int i2c_del_driver(struct i2c_driver *driver)
{
	struct list_head   *item1, *item2, *_n;
	struct i2c_client  *client;
	struct i2c_adapter *adap;
	
	int res = 0;

	down(&core_lists);

	/* Have a look at each adapter, if clients of this driver are still
	 * attached. If so, detach them to be able to kill the driver 
	 * afterwards.
	 */
	pr_debug("i2c-core: unregister_driver - looking for clients.\n");
	/* removing clients does not depend on the notify flag, else 
	 * invalid operation might (will!) result, when using stale client
	 * pointers.
	 */
	list_for_each(item1,&adapters) {
		adap = list_entry(item1, struct i2c_adapter, list);
		dev_dbg(&adap->dev, "examining adapter\n");
		if (driver->detach_adapter) {
			if ((res = driver->detach_adapter(adap))) {
				dev_warn(&adap->dev, "while unregistering "
				       "dummy driver %s, adapter could "
				       "not be detached properly; driver "
				       "not unloaded!",driver->name);
				goto out_unlock;
			}
		} else {
			list_for_each_safe(item2, _n, &adap->clients) {
				client = list_entry(item2, struct i2c_client, list);
				if (client->driver != driver)
					continue;
				pr_debug("i2c-core.o: detaching client %s:\n", client->name);
				if ((res = driver->detach_client(client))) {
					dev_err(&adap->dev, "while "
						"unregistering driver "
						"`%s', the client at "
						"address %02x of "
						"adapter could not "
						"be detached; driver "
						"not unloaded!",
						driver->name,
						client->addr);
					goto out_unlock;
				}
			}
		}
	}

	driver_unregister(&driver->driver);
	list_del(&driver->list);
	pr_debug("i2c-core: driver unregistered: %s\n", driver->name);

 out_unlock:
	up(&core_lists);
	return 0;
}

static int __i2c_check_addr(struct i2c_adapter *adapter, unsigned int addr)
{
	struct list_head   *item;
	struct i2c_client  *client;

	list_for_each(item,&adapter->clients) {
		client = list_entry(item, struct i2c_client, list);
		if (client->addr == addr)
			return -EBUSY;
	}
	return 0;
}

int i2c_check_addr(struct i2c_adapter *adapter, int addr)
{
	int rval;

	down(&adapter->clist_lock);
	rval = __i2c_check_addr(adapter, addr);
	up(&adapter->clist_lock);

	return rval;
}

int i2c_attach_client(struct i2c_client *client)
{
	struct i2c_adapter *adapter = client->adapter;

	down(&adapter->clist_lock);
	if (__i2c_check_addr(client->adapter, client->addr)) {
		up(&adapter->clist_lock);
		return -EBUSY;
	}
	list_add_tail(&client->list,&adapter->clients);
	up(&adapter->clist_lock);
	
	if (adapter->client_register)  {
		if (adapter->client_register(client))  {
			dev_warn(&adapter->dev, "warning: client_register "
				"seems to have failed for client %02x\n",
				client->addr);
		}
	}

	dev_dbg(&adapter->dev, "client [%s] registered to adapter\n",
		client->name);

	if (client->flags & I2C_CLIENT_ALLOW_USE)
		client->usage_count = 0;

	client->dev.parent = &client->adapter->dev;
	client->dev.driver = &client->driver->driver;
	client->dev.bus = &i2c_bus_type;
	client->dev.release = &i2c_client_release;
	
	snprintf(&client->dev.bus_id[0], sizeof(client->dev.bus_id),
		"%d-%04x", i2c_adapter_id(adapter), client->addr);
	pr_debug("registering %s\n", client->dev.bus_id);
	device_register(&client->dev);
	device_create_file(&client->dev, &dev_attr_client_name);
	
	return 0;
}


int i2c_detach_client(struct i2c_client *client)
{
	struct i2c_adapter *adapter = client->adapter;
	int res = 0;
	
	if ((client->flags & I2C_CLIENT_ALLOW_USE) && (client->usage_count > 0))
		return -EBUSY;

	if (adapter->client_unregister)  {
		res = adapter->client_unregister(client);
		if (res) {
			dev_err(&client->dev,
			       "client_unregister [%s] failed, "
			       "client not detached", client->name);
			goto out;
		}
	}

	down(&adapter->clist_lock);
	list_del(&client->list);
	init_completion(&client->released);
	device_remove_file(&client->dev, &dev_attr_client_name);
	device_unregister(&client->dev);
	up(&adapter->clist_lock);
	wait_for_completion(&client->released);

 out:
	return res;
}

static int i2c_inc_use_client(struct i2c_client *client)
{

	if (!try_module_get(client->driver->owner))
		return -ENODEV;
	if (!try_module_get(client->adapter->owner)) {
		module_put(client->driver->owner);
		return -ENODEV;
	}

	return 0;
}

static void i2c_dec_use_client(struct i2c_client *client)
{
	module_put(client->driver->owner);
	module_put(client->adapter->owner);
}

int i2c_use_client(struct i2c_client *client)
{
	int ret;

	ret = i2c_inc_use_client(client);
	if (ret)
		return ret;

	if (client->flags & I2C_CLIENT_ALLOW_USE) {
		if (client->flags & I2C_CLIENT_ALLOW_MULTIPLE_USE)
			client->usage_count++;
		else if (client->usage_count > 0) 
			goto busy;
		else 
			client->usage_count++;
	}

	return 0;
 busy:
	i2c_dec_use_client(client);
	return -EBUSY;
}

int i2c_release_client(struct i2c_client *client)
{
	if(client->flags & I2C_CLIENT_ALLOW_USE) {
		if(client->usage_count>0)
			client->usage_count--;
		else {
			pr_debug("i2c-core: %s used one too many times\n",
				__FUNCTION__);
			return -EPERM;
		}
	}
	
	i2c_dec_use_client(client);
	
	return 0;
}

void i2c_clients_command(struct i2c_adapter *adap, unsigned int cmd, void *arg)
{
	struct list_head  *item;
	struct i2c_client *client;

	down(&adap->clist_lock);
	list_for_each(item,&adap->clients) {
		client = list_entry(item, struct i2c_client, list);
		if (!try_module_get(client->driver->owner))
			continue;
		if (NULL != client->driver->command) {
			up(&adap->clist_lock);
			client->driver->command(client,cmd,arg);
			down(&adap->clist_lock);
		}
		module_put(client->driver->owner);
       }
       up(&adap->clist_lock);
}

static int __init i2c_init(void)
{
	int retval;

	retval = bus_register(&i2c_bus_type);
	if (retval)
		return retval;
	retval = driver_register(&i2c_adapter_driver);
	if (retval)
		return retval;
	return class_register(&i2c_adapter_class);
}

static void __exit i2c_exit(void)
{
	class_unregister(&i2c_adapter_class);
	driver_unregister(&i2c_adapter_driver);
	bus_unregister(&i2c_bus_type);
}

subsys_initcall(i2c_init);
module_exit(i2c_exit);

/* ----------------------------------------------------
 * the functional interface to the i2c busses.
 * ----------------------------------------------------
 */

int i2c_transfer(struct i2c_adapter * adap, struct i2c_msg *msgs, int num)
{
	int ret;

	if (adap->algo->master_xfer) {
#ifdef DEBUG
		for (ret = 0; ret < num; ret++) {
			dev_dbg(&adap->dev, "master_xfer[%d] %c, addr=0x%02x, "
				"len=%d\n", ret, msgs[ret].flags & I2C_M_RD ?
				'R' : 'W', msgs[ret].addr, msgs[ret].len);
		}
#endif

		down(&adap->bus_lock);
		ret = adap->algo->master_xfer(adap,msgs,num);
		up(&adap->bus_lock);

		return ret;
	} else {
		dev_dbg(&adap->dev, "I2C level transfers not supported\n");
		return -ENOSYS;
	}
}

int i2c_master_send(struct i2c_client *client,const char *buf ,int count)
{
	int ret;
	struct i2c_adapter *adap=client->adapter;
	struct i2c_msg msg;

	if (client->adapter->algo->master_xfer) {
		msg.addr   = client->addr;
		msg.flags = client->flags & I2C_M_TEN;
		msg.len = count;
		msg.buf = (char *)buf;
	
		dev_dbg(&client->adapter->dev, "master_send: writing %d bytes.\n",
			count);
	
		down(&adap->bus_lock);
		ret = adap->algo->master_xfer(adap,&msg,1);
		up(&adap->bus_lock);

		/* if everything went ok (i.e. 1 msg transmitted), return #bytes
		 * transmitted, else error code.
		 */
		return (ret == 1 )? count : ret;
	} else {
		dev_err(&client->adapter->dev, "I2C level transfers not supported\n");
		return -ENOSYS;
	}
}

int i2c_master_recv(struct i2c_client *client, char *buf ,int count)
{
	struct i2c_adapter *adap=client->adapter;
	struct i2c_msg msg;
	int ret;
	if (client->adapter->algo->master_xfer) {
		msg.addr   = client->addr;
		msg.flags = client->flags & I2C_M_TEN;
		msg.flags |= I2C_M_RD;
		msg.len = count;
		msg.buf = buf;

		dev_dbg(&client->adapter->dev, "master_recv: reading %d bytes.\n",
			count);
	
		down(&adap->bus_lock);
		ret = adap->algo->master_xfer(adap,&msg,1);
		up(&adap->bus_lock);
	
		dev_dbg(&client->adapter->dev, "master_recv: return:%d (count:%d, addr:0x%02x)\n",
			ret, count, client->addr);
	
		/* if everything went ok (i.e. 1 msg transmitted), return #bytes
	 	* transmitted, else error code.
	 	*/
		return (ret == 1 )? count : ret;
	} else {
		dev_err(&client->adapter->dev, "I2C level transfers not supported\n");
		return -ENOSYS;
	}
}


int i2c_control(struct i2c_client *client,
	unsigned int cmd, unsigned long arg)
{
	int ret = 0;
	struct i2c_adapter *adap = client->adapter;

	dev_dbg(&client->adapter->dev, "i2c ioctl, cmd: 0x%x, arg: %#lx\n", cmd, arg);
	switch (cmd) {
		case I2C_RETRIES:
			adap->retries = arg;
			break;
		case I2C_TIMEOUT:
			adap->timeout = arg;
			break;
		default:
			if (adap->algo->algo_control!=NULL)
				ret = adap->algo->algo_control(adap,cmd,arg);
	}
	return ret;
}

/* ----------------------------------------------------
 * the i2c address scanning function
 * Will not work for 10-bit addresses!
 * ----------------------------------------------------
 */
int i2c_probe(struct i2c_adapter *adapter,
	      struct i2c_client_address_data *address_data,
	      int (*found_proc) (struct i2c_adapter *, int, int))
{
	int addr,i,found,err;
	int adap_id = i2c_adapter_id(adapter);

	/* Forget it if we can't probe using SMBUS_QUICK */
	if (! i2c_check_functionality(adapter,I2C_FUNC_SMBUS_QUICK))
		return -1;

	for (addr = 0x00; addr <= 0x7f; addr++) {

		/* Skip if already in use */
		if (i2c_check_addr(adapter,addr))
			continue;

		/* If it is in one of the force entries, we don't do any detection
		   at all */
		found = 0;

		for (i = 0; !found && (address_data->force[i] != I2C_CLIENT_END); i += 2) {
			if (((adap_id == address_data->force[i]) || 
			     (address_data->force[i] == ANY_I2C_BUS)) &&
			     (addr == address_data->force[i+1])) {
				dev_dbg(&adapter->dev, "found force parameter for adapter %d, addr %04x\n",
					adap_id, addr);
				if ((err = found_proc(adapter,addr,0)))
					return err;
				found = 1;
			}
		}
		if (found) 
			continue;

		/* If this address is in one of the ignores, we can forget about
		   it right now */
		for (i = 0;
		     !found && (address_data->ignore[i] != I2C_CLIENT_END);
		     i += 2) {
			if (((adap_id == address_data->ignore[i]) || 
			    ((address_data->ignore[i] == ANY_I2C_BUS))) &&
			    (addr == address_data->ignore[i+1])) {
				dev_dbg(&adapter->dev, "found ignore parameter for adapter %d, "
					"addr %04x\n", adap_id ,addr);
				found = 1;
			}
		}
		for (i = 0;
		     !found && (address_data->ignore_range[i] != I2C_CLIENT_END);
		     i += 3) {
			if (((adap_id == address_data->ignore_range[i]) ||
			    ((address_data->ignore_range[i]==ANY_I2C_BUS))) &&
			    (addr >= address_data->ignore_range[i+1]) &&
			    (addr <= address_data->ignore_range[i+2])) {
				dev_dbg(&adapter->dev, "found ignore_range parameter for adapter %d, "
					"addr %04x\n", adap_id,addr);
				found = 1;
			}
		}
		if (found) 
			continue;

		/* Now, we will do a detection, but only if it is in the normal or 
		   probe entries */  
		for (i = 0;
		     !found && (address_data->normal_i2c[i] != I2C_CLIENT_END);
		     i += 1) {
			if (addr == address_data->normal_i2c[i]) {
				found = 1;
				dev_dbg(&adapter->dev, "found normal i2c entry for adapter %d, "
					"addr %02x\n", adap_id, addr);
			}
		}

		for (i = 0;
		     !found && (address_data->normal_i2c_range[i] != I2C_CLIENT_END);
		     i += 2) {
			if ((addr >= address_data->normal_i2c_range[i]) &&
			    (addr <= address_data->normal_i2c_range[i+1])) {
				found = 1;
				dev_dbg(&adapter->dev, "found normal i2c_range entry for adapter %d, "
					"addr %04x\n", adap_id,addr);
			}
		}

		for (i = 0;
		     !found && (address_data->probe[i] != I2C_CLIENT_END);
		     i += 2) {
			if (((adap_id == address_data->probe[i]) ||
			    ((address_data->probe[i] == ANY_I2C_BUS))) &&
			    (addr == address_data->probe[i+1])) {
				found = 1;
				dev_dbg(&adapter->dev, "found probe parameter for adapter %d, "
					"addr %04x\n", adap_id,addr);
			}
		}
		for (i = 0;
		     !found && (address_data->probe_range[i] != I2C_CLIENT_END);
		     i += 3) {
			if (((adap_id == address_data->probe_range[i]) ||
			   (address_data->probe_range[i] == ANY_I2C_BUS)) &&
			   (addr >= address_data->probe_range[i+1]) &&
			   (addr <= address_data->probe_range[i+2])) {
				found = 1;
				dev_dbg(&adapter->dev, "found probe_range parameter for adapter %d, "
					"addr %04x\n", adap_id,addr);
			}
		}
		if (!found) 
			continue;

		/* OK, so we really should examine this address. First check
		   whether there is some client here at all! */
		if (i2c_smbus_xfer(adapter,addr,0,0,0,I2C_SMBUS_QUICK,NULL) >= 0)
			if ((err = found_proc(adapter,addr,-1)))
				return err;
	}
	return 0;
}

/*
 * return id number for a specific adapter
 */
int i2c_adapter_id(struct i2c_adapter *adap)
{
	return adap->nr;
}

struct i2c_adapter* i2c_get_adapter(int id)
{
	struct list_head   *item;
	struct i2c_adapter *adapter;
	
	down(&core_lists);
	list_for_each(item,&adapters) {
		adapter = list_entry(item, struct i2c_adapter, list);
		if (id == adapter->nr &&
		    try_module_get(adapter->owner)) {
			up(&core_lists);
			return adapter;
		}
	}
	up(&core_lists);
	return NULL;
}

void i2c_put_adapter(struct i2c_adapter *adap)
{
	module_put(adap->owner);
}

/* The SMBus parts */

#define POLY    (0x1070U << 3) 
static u8
crc8(u16 data)
{
	int i;
  
	for(i = 0; i < 8; i++) {
		if (data & 0x8000) 
			data = data ^ POLY;
		data = data << 1;
	}
	return (u8)(data >> 8);
}

/* CRC over count bytes in the first array plus the bytes in the rest
   array if it is non-null. rest[0] is the (length of rest) - 1
   and is included. */
static u8 i2c_smbus_partial_pec(u8 crc, int count, u8 *first, u8 *rest)
{
	int i;

	for(i = 0; i < count; i++)
		crc = crc8((crc ^ first[i]) << 8);
	if(rest != NULL)
		for(i = 0; i <= rest[0]; i++)
			crc = crc8((crc ^ rest[i]) << 8);
	return crc;
}

static u8 i2c_smbus_pec(int count, u8 *first, u8 *rest)
{
	return i2c_smbus_partial_pec(0, count, first, rest);
}

/* Returns new "size" (transaction type)
   Note that we convert byte to byte_data and byte_data to word_data
   rather than invent new xxx_PEC transactions. */
static int i2c_smbus_add_pec(u16 addr, u8 command, int size,
			     union i2c_smbus_data *data)
{
	u8 buf[3];

	buf[0] = addr << 1;
	buf[1] = command;
	switch(size) {
		case I2C_SMBUS_BYTE:
			data->byte = i2c_smbus_pec(2, buf, NULL);
			size = I2C_SMBUS_BYTE_DATA;
			break;
		case I2C_SMBUS_BYTE_DATA:
			buf[2] = data->byte;
			data->word = buf[2] ||
			            (i2c_smbus_pec(3, buf, NULL) << 8);
			size = I2C_SMBUS_WORD_DATA;
			break;
		case I2C_SMBUS_WORD_DATA:
			/* unsupported */
			break;
		case I2C_SMBUS_BLOCK_DATA:
			data->block[data->block[0] + 1] =
			             i2c_smbus_pec(2, buf, data->block);
			size = I2C_SMBUS_BLOCK_DATA_PEC;
			break;
	}
	return size;	
}

static int i2c_smbus_check_pec(u16 addr, u8 command, int size, u8 partial,
			       union i2c_smbus_data *data)
{
	u8 buf[3], rpec, cpec;

	buf[1] = command;
	switch(size) {
		case I2C_SMBUS_BYTE_DATA:
			buf[0] = (addr << 1) | 1;
			cpec = i2c_smbus_pec(2, buf, NULL);
			rpec = data->byte;
			break;
		case I2C_SMBUS_WORD_DATA:
			buf[0] = (addr << 1) | 1;
			buf[2] = data->word & 0xff;
			cpec = i2c_smbus_pec(3, buf, NULL);
			rpec = data->word >> 8;
			break;
		case I2C_SMBUS_WORD_DATA_PEC:
			/* unsupported */
			cpec = rpec = 0;
			break;
		case I2C_SMBUS_PROC_CALL_PEC:
			/* unsupported */
			cpec = rpec = 0;
			break;
		case I2C_SMBUS_BLOCK_DATA_PEC:
			buf[0] = (addr << 1);
			buf[2] = (addr << 1) | 1;
			cpec = i2c_smbus_pec(3, buf, data->block);
			rpec = data->block[data->block[0] + 1];
			break;
		case I2C_SMBUS_BLOCK_PROC_CALL_PEC:
			buf[0] = (addr << 1) | 1;
			rpec = i2c_smbus_partial_pec(partial, 1,
			                             buf, data->block);
			cpec = data->block[data->block[0] + 1];
			break;
		default:
			cpec = rpec = 0;
			break;
	}
	if (rpec != cpec) {
		pr_debug("i2c-core: Bad PEC 0x%02x vs. 0x%02x\n",
			rpec, cpec);
		return -1;
	}
	return 0;	
}

s32 i2c_smbus_write_quick(struct i2c_client *client, u8 value)
{
	return i2c_smbus_xfer(client->adapter,client->addr,client->flags,
 	                      value,0,I2C_SMBUS_QUICK,NULL);
}

s32 i2c_smbus_read_byte(struct i2c_client *client)
{
	union i2c_smbus_data data;
	if (i2c_smbus_xfer(client->adapter,client->addr,client->flags,
	                   I2C_SMBUS_READ,0,I2C_SMBUS_BYTE, &data))
		return -1;
	else
		return 0x0FF & data.byte;
}

s32 i2c_smbus_write_byte(struct i2c_client *client, u8 value)
{
	union i2c_smbus_data data;	/* only for PEC */
	return i2c_smbus_xfer(client->adapter,client->addr,client->flags,
	                      I2C_SMBUS_WRITE,value, I2C_SMBUS_BYTE,&data);
}

s32 i2c_smbus_read_byte_data(struct i2c_client *client, u8 command)
{
	union i2c_smbus_data data;
	if (i2c_smbus_xfer(client->adapter,client->addr,client->flags,
	                   I2C_SMBUS_READ,command, I2C_SMBUS_BYTE_DATA,&data))
		return -1;
	else
		return 0x0FF & data.byte;
}

s32 i2c_smbus_write_byte_data(struct i2c_client *client, u8 command, u8 value)
{
	union i2c_smbus_data data;
	data.byte = value;
	return i2c_smbus_xfer(client->adapter,client->addr,client->flags,
	                      I2C_SMBUS_WRITE,command,
	                      I2C_SMBUS_BYTE_DATA,&data);
}

s32 i2c_smbus_read_word_data(struct i2c_client *client, u8 command)
{
	union i2c_smbus_data data;
	if (i2c_smbus_xfer(client->adapter,client->addr,client->flags,
	                   I2C_SMBUS_READ,command, I2C_SMBUS_WORD_DATA, &data))
		return -1;
	else
		return 0x0FFFF & data.word;
}

s32 i2c_smbus_write_word_data(struct i2c_client *client, u8 command, u16 value)
{
	union i2c_smbus_data data;
	data.word = value;
	return i2c_smbus_xfer(client->adapter,client->addr,client->flags,
	                      I2C_SMBUS_WRITE,command,
	                      I2C_SMBUS_WORD_DATA,&data);
}

s32 i2c_smbus_write_block_data(struct i2c_client *client, u8 command,
			       u8 length, u8 *values)
{
	union i2c_smbus_data data;
	int i;
	if (length > I2C_SMBUS_BLOCK_MAX)
		length = I2C_SMBUS_BLOCK_MAX;
	for (i = 1; i <= length; i++)
		data.block[i] = values[i-1];
	data.block[0] = length;
	return i2c_smbus_xfer(client->adapter,client->addr,client->flags,
			      I2C_SMBUS_WRITE,command,
			      I2C_SMBUS_BLOCK_DATA,&data);
}

/* Returns the number of read bytes */
s32 i2c_smbus_read_i2c_block_data(struct i2c_client *client, u8 command, u8 *values)
{
	union i2c_smbus_data data;
	int i;
	if (i2c_smbus_xfer(client->adapter,client->addr,client->flags,
	                      I2C_SMBUS_READ,command,
	                      I2C_SMBUS_I2C_BLOCK_DATA,&data))
		return -1;
	else {
		for (i = 1; i <= data.block[0]; i++)
			values[i-1] = data.block[i];
		return data.block[0];
	}
}

/* Simulate a SMBus command using the i2c protocol 
   No checking of parameters is done!  */
static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr, 
                                   unsigned short flags,
                                   char read_write, u8 command, int size, 
                                   union i2c_smbus_data * data)
{
	/* So we need to generate a series of msgs. In the case of writing, we
	  need to use only one message; when reading, we need two. We initialize
	  most things with sane defaults, to keep the code below somewhat
	  simpler. */
	unsigned char msgbuf0[34];
	unsigned char msgbuf1[34];
	int num = read_write == I2C_SMBUS_READ?2:1;
	struct i2c_msg msg[2] = { { addr, flags, 1, msgbuf0 }, 
	                          { addr, flags | I2C_M_RD, 0, msgbuf1 }
	                        };
	int i;

	msgbuf0[0] = command;
	switch(size) {
	case I2C_SMBUS_QUICK:
		msg[0].len = 0;
		/* Special case: The read/write field is used as data */
		msg[0].flags = flags | (read_write==I2C_SMBUS_READ)?I2C_M_RD:0;
		num = 1;
		break;
	case I2C_SMBUS_BYTE:
		if (read_write == I2C_SMBUS_READ) {
			/* Special case: only a read! */
			msg[0].flags = I2C_M_RD | flags;
			num = 1;
		}
		break;
	case I2C_SMBUS_BYTE_DATA:
		if (read_write == I2C_SMBUS_READ)
			msg[1].len = 1;
		else {
			msg[0].len = 2;
			msgbuf0[1] = data->byte;
		}
		break;
	case I2C_SMBUS_WORD_DATA:
		if (read_write == I2C_SMBUS_READ)
			msg[1].len = 2;
		else {
			msg[0].len=3;
			msgbuf0[1] = data->word & 0xff;
			msgbuf0[2] = (data->word >> 8) & 0xff;
		}
		break;
	case I2C_SMBUS_PROC_CALL:
		num = 2; /* Special case */
		read_write = I2C_SMBUS_READ;
		msg[0].len = 3;
		msg[1].len = 2;
		msgbuf0[1] = data->word & 0xff;
		msgbuf0[2] = (data->word >> 8) & 0xff;
		break;
	case I2C_SMBUS_BLOCK_DATA:
	case I2C_SMBUS_BLOCK_DATA_PEC:
		if (read_write == I2C_SMBUS_READ) {
			dev_err(&adapter->dev, "Block read not supported "
			       "under I2C emulation!\n");
			return -1;
		} else {
			msg[0].len = data->block[0] + 2;
			if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 2) {
				dev_err(&adapter->dev, "smbus_access called with "
				       "invalid block write size (%d)\n",
				       data->block[0]);
				return -1;
			}
			if(size == I2C_SMBUS_BLOCK_DATA_PEC)
				(msg[0].len)++;
			for (i = 1; i <= msg[0].len; i++)
				msgbuf0[i] = data->block[i-1];
		}
		break;
	case I2C_SMBUS_BLOCK_PROC_CALL:
	case I2C_SMBUS_BLOCK_PROC_CALL_PEC:
		dev_dbg(&adapter->dev, "Block process call not supported "
		       "under I2C emulation!\n");
		return -1;
	case I2C_SMBUS_I2C_BLOCK_DATA:
		if (read_write == I2C_SMBUS_READ) {
			msg[1].len = I2C_SMBUS_I2C_BLOCK_MAX;
		} else {
			msg[0].len = data->block[0] + 1;
			if (msg[0].len > I2C_SMBUS_I2C_BLOCK_MAX + 1) {
				dev_err(&adapter->dev, "i2c_smbus_xfer_emulated called with "
				       "invalid block write size (%d)\n",
				       data->block[0]);
				return -1;
			}
			for (i = 1; i <= data->block[0]; i++)
				msgbuf0[i] = data->block[i];
		}
		break;
	default:
		dev_err(&adapter->dev, "smbus_access called with invalid size (%d)\n",
		       size);
		return -1;
	}

	if (i2c_transfer(adapter, msg, num) < 0)
		return -1;

	if (read_write == I2C_SMBUS_READ)
		switch(size) {
			case I2C_SMBUS_BYTE:
				data->byte = msgbuf0[0];
				break;
			case I2C_SMBUS_BYTE_DATA:
				data->byte = msgbuf1[0];
				break;
			case I2C_SMBUS_WORD_DATA: 
			case I2C_SMBUS_PROC_CALL:
				data->word = msgbuf1[0] | (msgbuf1[1] << 8);
				break;
			case I2C_SMBUS_I2C_BLOCK_DATA:
				/* fixed at 32 for now */
				data->block[0] = I2C_SMBUS_I2C_BLOCK_MAX;
				for (i = 0; i < I2C_SMBUS_I2C_BLOCK_MAX; i++)
					data->block[i+1] = msgbuf1[i];
				break;
		}
	return 0;
}


s32 i2c_smbus_xfer(struct i2c_adapter * adapter, u16 addr, unsigned short flags,
                   char read_write, u8 command, int size, 
                   union i2c_smbus_data * data)
{
	s32 res;
	int swpec = 0;
	u8 partial = 0;

	flags &= I2C_M_TEN | I2C_CLIENT_PEC;
	if((flags & I2C_CLIENT_PEC) &&
	   !(i2c_check_functionality(adapter, I2C_FUNC_SMBUS_HWPEC_CALC))) {
		swpec = 1;
		if(read_write == I2C_SMBUS_READ &&
		   size == I2C_SMBUS_BLOCK_DATA)
			size = I2C_SMBUS_BLOCK_DATA_PEC;
		else if(size == I2C_SMBUS_PROC_CALL)
			size = I2C_SMBUS_PROC_CALL_PEC;
		else if(size == I2C_SMBUS_BLOCK_PROC_CALL) {
			i2c_smbus_add_pec(addr, command,
		                          I2C_SMBUS_BLOCK_DATA, data);
			partial = data->block[data->block[0] + 1];
			size = I2C_SMBUS_BLOCK_PROC_CALL_PEC;
		} else if(read_write == I2C_SMBUS_WRITE &&
		          size != I2C_SMBUS_QUICK &&
		          size != I2C_SMBUS_I2C_BLOCK_DATA)
			size = i2c_smbus_add_pec(addr, command, size, data);
	}

	if (adapter->algo->smbus_xfer) {
		down(&adapter->bus_lock);
		res = adapter->algo->smbus_xfer(adapter,addr,flags,read_write,
		                                command,size,data);
		up(&adapter->bus_lock);
	} else
		res = i2c_smbus_xfer_emulated(adapter,addr,flags,read_write,
	                                      command,size,data);

	if(res >= 0 && swpec &&
	   size != I2C_SMBUS_QUICK && size != I2C_SMBUS_I2C_BLOCK_DATA &&
	   (read_write == I2C_SMBUS_READ || size == I2C_SMBUS_PROC_CALL_PEC ||
	    size == I2C_SMBUS_BLOCK_PROC_CALL_PEC)) {
		if(i2c_smbus_check_pec(addr, command, size, partial, data))
			return -1;
	}
	return res;
}


EXPORT_SYMBOL(i2c_add_adapter);
EXPORT_SYMBOL(i2c_del_adapter);
EXPORT_SYMBOL(i2c_add_driver);
EXPORT_SYMBOL(i2c_del_driver);
EXPORT_SYMBOL(i2c_attach_client);
EXPORT_SYMBOL(i2c_detach_client);
EXPORT_SYMBOL(i2c_use_client);
EXPORT_SYMBOL(i2c_release_client);
EXPORT_SYMBOL(i2c_clients_command);
EXPORT_SYMBOL(i2c_check_addr);

EXPORT_SYMBOL(i2c_master_send);
EXPORT_SYMBOL(i2c_master_recv);
EXPORT_SYMBOL(i2c_control);
EXPORT_SYMBOL(i2c_transfer);
EXPORT_SYMBOL(i2c_adapter_id);
EXPORT_SYMBOL(i2c_get_adapter);
EXPORT_SYMBOL(i2c_put_adapter);
EXPORT_SYMBOL(i2c_probe);

EXPORT_SYMBOL(i2c_smbus_xfer);
EXPORT_SYMBOL(i2c_smbus_write_quick);
EXPORT_SYMBOL(i2c_smbus_read_byte);
EXPORT_SYMBOL(i2c_smbus_write_byte);
EXPORT_SYMBOL(i2c_smbus_read_byte_data);
EXPORT_SYMBOL(i2c_smbus_write_byte_data);
EXPORT_SYMBOL(i2c_smbus_read_word_data);
EXPORT_SYMBOL(i2c_smbus_write_word_data);
EXPORT_SYMBOL(i2c_smbus_write_block_data);
EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data);

MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
MODULE_DESCRIPTION("I2C-Bus main module");
MODULE_LICENSE("GPL");