/* 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/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);

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);
}

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);
}

void i2c_adapter_dev_release(struct device *dev)
{
   struct i2c_adapter *adap = dev_to_i2c_adapter(dev);

   complete(&adap->dev_released);
}

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);
}

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

static ssize_t show_adapter_name(struct device *dev, struct device_attribute *attr, 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, struct device_attribute *attr, 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, adap, &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);

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

   /* 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);
      }
   }

 out_unlock:
   up(&core_lists);
   return(res);
} /* i2c_add_adapter */


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-core: attempting to delete unregistered "
               "adapter [%s]\n", adap->name);
      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_err(&adap->dev, "detach_adapter failed "
                    "for driver [%s]\n", driver->name);
            goto out_unlock;
         }
      }
   }

   /* detach any active clients. This must be done first, because
    * it can fail; in which case we give up. */
   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, "detach_client failed for client "
                 "[%s] at address 0x%02x\n", client->name,
                 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 [%s] unregistered\n", adap->name);

 out_unlock:
   up(&core_lists);
   return(res);
} /* i2c_del_adapter */


/* -----
 * 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.
    *
    * 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);
      if (driver->detach_adapter)
      {
         if ((res = driver->detach_adapter(adap)))
         {
            dev_err(&adap->dev, "detach_adapter failed "
                    "for driver [%s]\n", 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;
            }
            dev_dbg(&adap->dev, "detaching client [%s] "
                    "at 0x%02x\n", client->name,
                    client->addr);
            if ((res = driver->detach_client(client)))
            {
               dev_err(&adap->dev, "detach_client "
                       "failed for client [%s] at "
                       "0x%02x\n", client->name,
                       client->addr);
               goto out_unlock;
            }
         }
      }
   }

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

 out_unlock:
   up(&core_lists);
   return(0);
} /* i2c_del_driver */

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_dbg(&adapter->dev, "client_register "
                 "failed for client [%s] at 0x%02x\n",
                 client->name, client->addr);
      }
   }

   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);
   dev_dbg(&adapter->dev, "client [%s] registered with bus id %s\n",
           client->name, client->dev.bus_id);
   device_register(&client->dev);
   device_create_file(&client->dev, &dev_attr_client_name);

   return(0);
} /* i2c_attach_client */


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))
   {
      dev_warn(&client->dev, "Client [%s] still busy, "
               "can't detach\n", client->name);
      return(-EBUSY);
   }

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

   msg.addr  = client->addr;
   msg.flags = client->flags & I2C_M_TEN;
   msg.len   = count;
   msg.buf   = (char *)buf;

   ret = i2c_transfer(adap, &msg, 1);

   /* If everything went ok (i.e. 1 msg transmitted), return #bytes
    * transmitted, else error code. */
   return((ret == 1) ? count : ret);
}

int i2c_master_recv(struct i2c_client *client, char *buf, int count)
{
   struct i2c_adapter *adap = client->adapter;
   struct i2c_msg     msg;
   int                ret;

   msg.addr   = client->addr;
   msg.flags  = client->flags & I2C_M_TEN;
   msg.flags |= I2C_M_RD;
   msg.len    = count;
   msg.buf    = buf;

   ret = i2c_transfer(adap, &msg, 1);

   /* If everything went ok (i.e. 1 msg transmitted), return #bytes
    * transmitted, else error code. */
   return((ret == 1) ? count : ret);
}


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!
 * ----------------------------------------------------
 */
static int i2c_probe_address(struct i2c_adapter *adapter, int addr, int kind,
                             int (*found_proc) (struct i2c_adapter *, int, int))
{
   int err;

   /* Make sure the address is valid */
   if (addr < 0x03 || addr > 0x77)
   {
      dev_warn(&adapter->dev, "Invalid probe address 0x%02x\n",
               addr);
      return(-EINVAL);
   }

   /* Skip if already in use */
   if (i2c_check_addr(adapter, addr))
   {
      return(0);
   }

   /* Make sure there is something at this address, unless forced */
   if (kind < 0)
   {
      if (i2c_smbus_xfer(adapter, addr, 0, 0, 0,
                         I2C_SMBUS_QUICK, NULL) < 0)
      {
         return(0);
      }

      /* prevent 24RF08 corruption */
      if ((addr & ~0x0f) == 0x50)
      {
         i2c_smbus_xfer(adapter, addr, 0, 0, 0,
                        I2C_SMBUS_QUICK, NULL);
      }
   }

   /* Finally call the custom detection function */
   err = found_proc(adapter, addr, kind);

   /* -ENODEV can be returned if there is a chip at the given address
    * but it isn't supported by this chip driver. We catch it here as
    * this isn't an error. */
   return((err == -ENODEV) ? 0 : err);
}

int i2c_probe(struct i2c_adapter *adapter,
              struct i2c_client_address_data *address_data,
              int (*found_proc) (struct i2c_adapter *, int, int))
{
   int i, 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);
   }

   /* Force entries are done first, and are not affected by ignore
    * entries */
   if (address_data->forces)
   {
      unsigned short **forces = address_data->forces;
      int            kind;

      for (kind = 0; forces[kind]; kind++)
      {
         for (i = 0; forces[kind][i] != I2C_CLIENT_END;
              i += 2)
         {
            if (forces[kind][i] == adap_id
                || forces[kind][i] == ANY_I2C_BUS)
            {
               dev_dbg(&adapter->dev, "found force "
                       "parameter for adapter %d, "
                       "addr 0x%02x, kind %d\n",
                       adap_id, forces[kind][i + 1],
                       kind);
               err = i2c_probe_address(adapter,
                                       forces[kind][i + 1],
                                       kind, found_proc);
               if (err)
               {
                  return(err);
               }
            }
         }
      }
   }

   /* Probe entries are done second, and are not affected by ignore
    * entries either */
   for (i = 0; address_data->probe[i] != I2C_CLIENT_END; i += 2)
   {
      if (address_data->probe[i] == adap_id
          || address_data->probe[i] == ANY_I2C_BUS)
      {
         dev_dbg(&adapter->dev, "found probe parameter for "
                 "adapter %d, addr 0x%02x\n", adap_id,
                 address_data->probe[i + 1]);
         err = i2c_probe_address(adapter,
                                 address_data->probe[i + 1],
                                 -1, found_proc);
         if (err)
         {
            return(err);
         }
      }
   }

   /* Normal entries are done last, unless shadowed by an ignore entry */
   for (i = 0; address_data->normal_i2c[i] != I2C_CLIENT_END; i += 1)
   {
      int j, ignore;

      ignore = 0;
      for (j = 0; address_data->ignore[j] != I2C_CLIENT_END;
           j += 2)
      {
         if ((address_data->ignore[j] == adap_id ||
              address_data->ignore[j] == ANY_I2C_BUS)
             && address_data->ignore[j + 1]
             == address_data->normal_i2c[i])
         {
            dev_dbg(&adapter->dev, "found ignore "
                    "parameter for adapter %d, "
                    "addr 0x%02x\n", adap_id,
                    address_data->ignore[j + 1]);
         }
         ignore = 1;
         break;
      }
      if (ignore)
      {
         continue;
      }

      dev_dbg(&adapter->dev, "found normal entry for adapter %d, "
              "addr 0x%02x\n", adap_id,
              address_data->normal_i2c[i]);
      err = i2c_probe_address(adapter, address_data->normal_i2c[i],
                              -1, found_proc);
      if (err)
      {
         return(err);
      }
   }

   return(0);
} /* i2c_probe */

struct i2c_adapter *i2c_get_adapter(int id)
{
   struct i2c_adapter *adapter;

   down(&core_lists);
   adapter = (struct i2c_adapter *)idr_find(&i2c_adapter_idr, id);
   if (adapter && !try_module_get(adapter->owner))
   {
      adapter = NULL;
   }

   up(&core_lists);
   return(adapter);
}

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;
   } /* switch */
   if (rpec != cpec)
   {
      pr_debug("i2c-core: Bad PEC 0x%02x vs. 0x%02x\n",
               rpec, cpec);
      return(-1);
   }
   return(0);
} /* i2c_smbus_check_pec */

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);
   } /* switch */

   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);
} /* i2c_smbus_xfer_emulated */


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);
} /* i2c_smbus_xfer */


/* Next four are needed by i2c-isa */
EXPORT_SYMBOL_GPL(i2c_adapter_dev_release);
EXPORT_SYMBOL_GPL(i2c_adapter_driver);
EXPORT_SYMBOL_GPL(i2c_adapter_class);
EXPORT_SYMBOL_GPL(i2c_bus_type);

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_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");
