i2c-core.c

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

/* With some changes from Kyösti Mälkki <[email protected]>.
   All SMBus-related things are written by Frodo Looijaard <[email protected]>
   SMBus 2.0 support by Mark Studebaker <[email protected]> and
   Jean Delvare <[email protected]>
   Mux support by Rodolfo Giometti <[email protected]> and
   Michael Lawnick <[email protected]> */

#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/mutex.h>
#include <linux/of_device.h>
#include <linux/completion.h>
#include <linux/hardirq.h>
#include <linux/irqflags.h>
#include <linux/rwsem.h>
#include <linux/pm_runtime.h>
#include <asm/uaccess.h>

#include "i2c-core.h"


/* core_lock protects i2c_adapter_idr, and guarantees
   that device detection, deletion of detected devices, and attach_adapter
   and detach_adapter calls are serialized */
static DEFINE_MUTEX(core_lock);
static DEFINE_IDR(i2c_adapter_idr);

static struct device_type i2c_client_type;
static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver);

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

static const struct i2c_device_id *i2c_match_id(const struct i2c_device_id *id,
                        const struct i2c_client *client)
{
    while (id->name[0]) {
        if (strcmp(client->name, id->name) == 0)
            return id;
        id++;
    }
    return NULL;
}

static int i2c_device_match(struct device *dev, struct device_driver *drv)
{
    struct i2c_client   *client = i2c_verify_client(dev);
    struct i2c_driver   *driver;

    if (!client)
        return 0;

    /* Attempt an OF style match */
    if (of_driver_match_device(dev, drv))
        return 1;

    driver = to_i2c_driver(drv);
    /* match on an id table if there is one */
    if (driver->id_table)
        return i2c_match_id(driver->id_table, client) != NULL;

    return 0;
}

#ifdef  CONFIG_HOTPLUG

/* uevent helps with hotplug: modprobe -q $(MODALIAS) */
static int i2c_device_uevent(struct device *dev, struct kobj_uevent_env *env)
{
    struct i2c_client   *client = to_i2c_client(dev);

    if (add_uevent_var(env, "MODALIAS=%s%s",
               I2C_MODULE_PREFIX, client->name))
        return -ENOMEM;
    dev_dbg(dev, "uevent\n");
    return 0;
}

#else
#define i2c_device_uevent   NULL
#endif  /* CONFIG_HOTPLUG */

static int i2c_device_probe(struct device *dev)
{
    struct i2c_client   *client = i2c_verify_client(dev);
    struct i2c_driver   *driver;
    int status;

    if (!client)
        return 0;

    driver = to_i2c_driver(dev->driver);
    if (!driver->probe || !driver->id_table)
        return -ENODEV;
    client->driver = driver;
    if (!device_can_wakeup(&client->dev))
        device_init_wakeup(&client->dev,
                    client->flags & I2C_CLIENT_WAKE);
    dev_dbg(dev, "probe\n");

    status = driver->probe(client, i2c_match_id(driver->id_table, client));
    if (status) {
        client->driver = NULL;
        i2c_set_clientdata(client, NULL);
    }
    return status;
}

static int i2c_device_remove(struct device *dev)
{
    struct i2c_client   *client = i2c_verify_client(dev);
    struct i2c_driver   *driver;
    int         status;

    if (!client || !dev->driver)
        return 0;

    driver = to_i2c_driver(dev->driver);
    if (driver->remove) {
        dev_dbg(dev, "remove\n");
        status = driver->remove(client);
    } else {
        dev->driver = NULL;
        status = 0;
    }
    if (status == 0) {
        client->driver = NULL;
        i2c_set_clientdata(client, NULL);
    }
    return status;
}

static void i2c_device_shutdown(struct device *dev)
{
    struct i2c_client *client = i2c_verify_client(dev);
    struct i2c_driver *driver;

    if (!client || !dev->driver)
        return;
    driver = to_i2c_driver(dev->driver);
    if (driver->shutdown)
        driver->shutdown(client);
}

#ifdef CONFIG_PM_SLEEP
static int i2c_legacy_suspend(struct device *dev, pm_message_t mesg)
{
    struct i2c_client *client = i2c_verify_client(dev);
    struct i2c_driver *driver;

    if (!client || !dev->driver)
        return 0;
    driver = to_i2c_driver(dev->driver);
    if (!driver->suspend)
        return 0;
    return driver->suspend(client, mesg);
}

static int i2c_legacy_resume(struct device *dev)
{
    struct i2c_client *client = i2c_verify_client(dev);
    struct i2c_driver *driver;

    if (!client || !dev->driver)
        return 0;
    driver = to_i2c_driver(dev->driver);
    if (!driver->resume)
        return 0;
    return driver->resume(client);
}

static int i2c_device_pm_suspend(struct device *dev)
{
    const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

    if (pm)
        return pm_generic_suspend(dev);
    else
        return i2c_legacy_suspend(dev, PMSG_SUSPEND);
}

static int i2c_device_pm_resume(struct device *dev)
{
    const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

    if (pm)
        return pm_generic_resume(dev);
    else
        return i2c_legacy_resume(dev);
}

static int i2c_device_pm_freeze(struct device *dev)
{
    const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

    if (pm)
        return pm_generic_freeze(dev);
    else
        return i2c_legacy_suspend(dev, PMSG_FREEZE);
}

static int i2c_device_pm_thaw(struct device *dev)
{
    const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

    if (pm)
        return pm_generic_thaw(dev);
    else
        return i2c_legacy_resume(dev);
}

static int i2c_device_pm_poweroff(struct device *dev)
{
    const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

    if (pm)
        return pm_generic_poweroff(dev);
    else
        return i2c_legacy_suspend(dev, PMSG_HIBERNATE);
}

static int i2c_device_pm_restore(struct device *dev)
{
    const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

    if (pm)
        return pm_generic_restore(dev);
    else
        return i2c_legacy_resume(dev);
}
#else /* !CONFIG_PM_SLEEP */
#define i2c_device_pm_suspend   NULL
#define i2c_device_pm_resume    NULL
#define i2c_device_pm_freeze    NULL
#define i2c_device_pm_thaw  NULL
#define i2c_device_pm_poweroff  NULL
#define i2c_device_pm_restore   NULL
#endif /* !CONFIG_PM_SLEEP */

static void i2c_client_dev_release(struct device *dev)
{
    kfree(to_i2c_client(dev));
}

static ssize_t
show_name(struct device *dev, struct device_attribute *attr, char *buf)
{
    return sprintf(buf, "%s\n", dev->type == &i2c_client_type ?
               to_i2c_client(dev)->name : to_i2c_adapter(dev)->name);
}

static ssize_t
show_modalias(struct device *dev, struct device_attribute *attr, char *buf)
{
    struct i2c_client *client = to_i2c_client(dev);
    return sprintf(buf, "%s%s\n", I2C_MODULE_PREFIX, client->name);
}

static DEVICE_ATTR(name, S_IRUGO, show_name, NULL);
static DEVICE_ATTR(modalias, S_IRUGO, show_modalias, NULL);

static struct attribute *i2c_dev_attrs[] = {
    &dev_attr_name.attr,
    /* modalias helps coldplug:  modprobe $(cat .../modalias) */
    &dev_attr_modalias.attr,
    NULL
};

static struct attribute_group i2c_dev_attr_group = {
    .attrs      = i2c_dev_attrs,
};

static const struct attribute_group *i2c_dev_attr_groups[] = {
    &i2c_dev_attr_group,
    NULL
};

static const struct dev_pm_ops i2c_device_pm_ops = {
    .suspend = i2c_device_pm_suspend,
    .resume = i2c_device_pm_resume,
    .freeze = i2c_device_pm_freeze,
    .thaw = i2c_device_pm_thaw,
    .poweroff = i2c_device_pm_poweroff,
    .restore = i2c_device_pm_restore,
    SET_RUNTIME_PM_OPS(
        pm_generic_runtime_suspend,
        pm_generic_runtime_resume,
        pm_generic_runtime_idle
    )
};

struct bus_type i2c_bus_type = {
    .name       = "i2c",
    .match      = i2c_device_match,
    .probe      = i2c_device_probe,
    .remove     = i2c_device_remove,
    .shutdown   = i2c_device_shutdown,
    .pm     = &i2c_device_pm_ops,
};
EXPORT_SYMBOL_GPL(i2c_bus_type);

static struct device_type i2c_client_type = {
    .groups     = i2c_dev_attr_groups,
    .uevent     = i2c_device_uevent,
    .release    = i2c_client_dev_release,
};


struct i2c_client *i2c_verify_client(struct device *dev)
{
    return (dev->type == &i2c_client_type)
            ? to_i2c_client(dev)
            : NULL;
}
EXPORT_SYMBOL(i2c_verify_client);


/* This is a permissive address validity check, I2C address map constraints
 * are purposely not enforced, except for the general call address. */
static int i2c_check_client_addr_validity(const struct i2c_client *client)
{
    if (client->flags & I2C_CLIENT_TEN) {
        /* 10-bit address, all values are valid */
        if (client->addr > 0x3ff)
            return -EINVAL;
    } else {
        /* 7-bit address, reject the general call address */
        if (client->addr == 0x00 || client->addr > 0x7f)
            return -EINVAL;
    }
    return 0;
}

/* And this is a strict address validity check, used when probing. If a
 * device uses a reserved address, then it shouldn't be probed. 7-bit
 * addressing is assumed, 10-bit address devices are rare and should be
 * explicitly enumerated. */
static int i2c_check_addr_validity(unsigned short addr)
{
    /*
     * Reserved addresses per I2C specification:
     *  0x00       General call address / START byte
     *  0x01       CBUS address
     *  0x02       Reserved for different bus format
     *  0x03       Reserved for future purposes
     *  0x04-0x07  Hs-mode master code
     *  0x78-0x7b  10-bit slave addressing
     *  0x7c-0x7f  Reserved for future purposes
     */
    if (addr < 0x08 || addr > 0x77)
        return -EINVAL;
    return 0;
}

static int __i2c_check_addr_busy(struct device *dev, void *addrp)
{
    struct i2c_client   *client = i2c_verify_client(dev);
    int         addr = *(int *)addrp;

    if (client && client->addr == addr)
        return -EBUSY;
    return 0;
}

/* walk up mux tree */
static int i2c_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,
                    __i2c_check_addr_busy);

    if (!result && parent)
        result = i2c_check_mux_parents(parent, addr);

    return result;
}

/* recurse down mux tree */
static int i2c_check_mux_children(struct device *dev, void *addrp)
{
    int result;

    if (dev->type == &i2c_adapter_type)
        result = device_for_each_child(dev, addrp,
                        i2c_check_mux_children);
    else
        result = __i2c_check_addr_busy(dev, addrp);

    return result;
}

static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr)
{
    struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
    int result = 0;

    if (parent)
        result = i2c_check_mux_parents(parent, addr);

    if (!result)
        result = device_for_each_child(&adapter->dev, &addr,
                        i2c_check_mux_children);

    return result;
}

void i2c_lock_adapter(struct i2c_adapter *adapter)
{
    struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);

    if (parent)
        i2c_lock_adapter(parent);
    else
        rt_mutex_lock(&adapter->bus_lock);
}
EXPORT_SYMBOL_GPL(i2c_lock_adapter);

static int i2c_trylock_adapter(struct i2c_adapter *adapter)
{
    struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);

    if (parent)
        return i2c_trylock_adapter(parent);
    else
        return rt_mutex_trylock(&adapter->bus_lock);
}

void i2c_unlock_adapter(struct i2c_adapter *adapter)
{
    struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);

    if (parent)
        i2c_unlock_adapter(parent);
    else
        rt_mutex_unlock(&adapter->bus_lock);
}
EXPORT_SYMBOL_GPL(i2c_unlock_adapter);

struct i2c_client *
i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
{
    struct i2c_client   *client;
    int         status;

    client = kzalloc(sizeof *client, GFP_KERNEL);
    if (!client)
        return NULL;

    client->adapter = adap;

    client->dev.platform_data = info->platform_data;

    if (info->archdata)
        client->dev.archdata = *info->archdata;

    client->flags = info->flags;
    client->addr = info->addr;
    client->irq = info->irq;

    strlcpy(client->name, info->type, sizeof(client->name));

    /* Check for address validity */
    status = i2c_check_client_addr_validity(client);
    if (status) {
        dev_err(&adap->dev, "Invalid %d-bit I2C address 0x%02hx\n",
            client->flags & I2C_CLIENT_TEN ? 10 : 7, client->addr);
        goto out_err_silent;
    }

    /* Check for address business */
    status = i2c_check_addr_busy(adap, client->addr);
    if (status)
        goto out_err;

    client->dev.parent = &client->adapter->dev;
    client->dev.bus = &i2c_bus_type;
    client->dev.type = &i2c_client_type;
    client->dev.of_node = info->of_node;

    /* For 10-bit clients, add an arbitrary offset to avoid collisions */
    dev_set_name(&client->dev, "%d-%04x", i2c_adapter_id(adap),
             client->addr | ((client->flags & I2C_CLIENT_TEN)
                     ? 0xa000 : 0));
    status = device_register(&client->dev);
    if (status)
        goto out_err;

    dev_dbg(&adap->dev, "client [%s] registered with bus id %s\n",
        client->name, dev_name(&client->dev));

    return client;

out_err:
    dev_err(&adap->dev, "Failed to register i2c client %s at 0x%02x "
        "(%d)\n", client->name, client->addr, status);
out_err_silent:
    kfree(client);
    return NULL;
}
EXPORT_SYMBOL_GPL(i2c_new_device);


void i2c_unregister_device(struct i2c_client *client)
{
    device_unregister(&client->dev);
}
EXPORT_SYMBOL_GPL(i2c_unregister_device);


static const struct i2c_device_id dummy_id[] = {
    { "dummy", 0 },
    { },
};

static int dummy_probe(struct i2c_client *client,
               const struct i2c_device_id *id)
{
    return 0;
}

static int dummy_remove(struct i2c_client *client)
{
    return 0;
}

static struct i2c_driver dummy_driver = {
    .driver.name    = "dummy",
    .probe      = dummy_probe,
    .remove     = dummy_remove,
    .id_table   = dummy_id,
};

struct i2c_client *i2c_new_dummy(struct i2c_adapter *adapter, u16 address)
{
    struct i2c_board_info info = {
        I2C_BOARD_INFO("dummy", address),
    };

    return i2c_new_device(adapter, &info);
}
EXPORT_SYMBOL_GPL(i2c_new_dummy);

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

/* I2C bus adapters -- one roots each I2C or SMBUS segment */

static void i2c_adapter_dev_release(struct device *dev)
{
    struct i2c_adapter *adap = to_i2c_adapter(dev);
    complete(&adap->dev_released);
}

/*
 * This function is only needed for mutex_lock_nested, so it is never
 * called unless locking correctness checking is enabled. Thus we
 * make it inline to avoid a compiler warning. That's what gcc ends up
 * doing anyway.
 */
static inline unsigned int i2c_adapter_depth(struct i2c_adapter *adapter)
{
    unsigned int depth = 0;

    while ((adapter = i2c_parent_is_i2c_adapter(adapter)))
        depth++;

    return depth;
}

/*
 * Let users instantiate I2C devices through sysfs. This can be used when
 * platform initialization code doesn't contain the proper data for
 * whatever reason. Also useful for drivers that do device detection and
 * detection fails, either because the device uses an unexpected address,
 * or this is a compatible device with different ID register values.
 *
 * Parameter checking may look overzealous, but we really don't want
 * the user to provide incorrect parameters.
 */
static ssize_t
i2c_sysfs_new_device(struct device *dev, struct device_attribute *attr,
             const char *buf, size_t count)
{
    struct i2c_adapter *adap = to_i2c_adapter(dev);
    struct i2c_board_info info;
    struct i2c_client *client;
    char *blank, end;
    int res;

    memset(&info, 0, sizeof(struct i2c_board_info));

    blank = strchr(buf, ' ');
    if (!blank) {
        dev_err(dev, "%s: Missing parameters\n", "new_device");
        return -EINVAL;
    }
    if (blank - buf > I2C_NAME_SIZE - 1) {
        dev_err(dev, "%s: Invalid device name\n", "new_device");
        return -EINVAL;
    }
    memcpy(info.type, buf, blank - buf);

    /* Parse remaining parameters, reject extra parameters */
    res = sscanf(++blank, "%hi%c", &info.addr, &end);
    if (res < 1) {
        dev_err(dev, "%s: Can't parse I2C address\n", "new_device");
        return -EINVAL;
    }
    if (res > 1  && end != '\n') {
        dev_err(dev, "%s: Extra parameters\n", "new_device");
        return -EINVAL;
    }

    client = i2c_new_device(adap, &info);
    if (!client)
        return -EINVAL;

    /* Keep track of the added device */
    mutex_lock(&adap->userspace_clients_lock);
    list_add_tail(&client->detected, &adap->userspace_clients);
    mutex_unlock(&adap->userspace_clients_lock);
    dev_info(dev, "%s: Instantiated device %s at 0x%02hx\n", "new_device",
         info.type, info.addr);

    return count;
}

/*
 * And of course let the users delete the devices they instantiated, if
 * they got it wrong. This interface can only be used to delete devices
 * instantiated by i2c_sysfs_new_device above. This guarantees that we
 * don't delete devices to which some kernel code still has references.
 *
 * Parameter checking may look overzealous, but we really don't want
 * the user to delete the wrong device.
 */
static ssize_t
i2c_sysfs_delete_device(struct device *dev, struct device_attribute *attr,
            const char *buf, size_t count)
{
    struct i2c_adapter *adap = to_i2c_adapter(dev);
    struct i2c_client *client, *next;
    unsigned short addr;
    char end;
    int res;

    /* Parse parameters, reject extra parameters */
    res = sscanf(buf, "%hi%c", &addr, &end);
    if (res < 1) {
        dev_err(dev, "%s: Can't parse I2C address\n", "delete_device");
        return -EINVAL;
    }
    if (res > 1  && end != '\n') {
        dev_err(dev, "%s: Extra parameters\n", "delete_device");
        return -EINVAL;
    }

    /* Make sure the device was added through sysfs */
    res = -ENOENT;
    mutex_lock_nested(&adap->userspace_clients_lock,
              i2c_adapter_depth(adap));
    list_for_each_entry_safe(client, next, &adap->userspace_clients,
                 detected) {
        if (client->addr == addr) {
            dev_info(dev, "%s: Deleting device %s at 0x%02hx\n",
                 "delete_device", client->name, client->addr);

            list_del(&client->detected);
            i2c_unregister_device(client);
            res = count;
            break;
        }
    }
    mutex_unlock(&adap->userspace_clients_lock);

    if (res < 0)
        dev_err(dev, "%s: Can't find device in list\n",
            "delete_device");
    return res;
}

static DEVICE_ATTR(new_device, S_IWUSR, NULL, i2c_sysfs_new_device);
static DEVICE_ATTR(delete_device, S_IWUSR, NULL, i2c_sysfs_delete_device);

static struct attribute *i2c_adapter_attrs[] = {
    &dev_attr_name.attr,
    &dev_attr_new_device.attr,
    &dev_attr_delete_device.attr,
    NULL
};

static struct attribute_group i2c_adapter_attr_group = {
    .attrs      = i2c_adapter_attrs,
};

static const struct attribute_group *i2c_adapter_attr_groups[] = {
    &i2c_adapter_attr_group,
    NULL
};

struct device_type i2c_adapter_type = {
    .groups     = i2c_adapter_attr_groups,
    .release    = i2c_adapter_dev_release,
};
EXPORT_SYMBOL_GPL(i2c_adapter_type);

struct i2c_adapter *i2c_verify_adapter(struct device *dev)
{
    return (dev->type == &i2c_adapter_type)
            ? to_i2c_adapter(dev)
            : NULL;
}
EXPORT_SYMBOL(i2c_verify_adapter);

#ifdef CONFIG_I2C_COMPAT
static struct class_compat *i2c_adapter_compat_class;
#endif

static void i2c_scan_static_board_info(struct i2c_adapter *adapter)
{
    struct i2c_devinfo  *devinfo;

    down_read(&__i2c_board_lock);
    list_for_each_entry(devinfo, &__i2c_board_list, list) {
        if (devinfo->busnum == adapter->nr
                && !i2c_new_device(adapter,
                        &devinfo->board_info))
            dev_err(&adapter->dev,
                "Can't create device at 0x%02x\n",
                devinfo->board_info.addr);
    }
    up_read(&__i2c_board_lock);
}

static int i2c_do_add_adapter(struct i2c_driver *driver,
                  struct i2c_adapter *adap)
{
    /* Detect supported devices on that bus, and instantiate them */
    i2c_detect(adap, driver);

    /* Let legacy drivers scan this bus for matching devices */
    if (driver->attach_adapter) {
        dev_warn(&adap->dev, "%s: attach_adapter method is deprecated\n",
             driver->driver.name);
        dev_warn(&adap->dev, "Please use another way to instantiate "
             "your i2c_client\n");
        /* We ignore the return code; if it fails, too bad */
        driver->attach_adapter(adap);
    }
    return 0;
}

static int __process_new_adapter(struct device_driver *d, void *data)
{
    return i2c_do_add_adapter(to_i2c_driver(d), data);
}

static int i2c_register_adapter(struct i2c_adapter *adap)
{
    int res = 0;

    /* Can't register until after driver model init */
    if (unlikely(WARN_ON(!i2c_bus_type.p))) {
        res = -EAGAIN;
        goto out_list;
    }

    /* Sanity checks */
    if (unlikely(adap->name[0] == '\0')) {
        pr_err("i2c-core: Attempt to register an adapter with "
               "no name!\n");
        return -EINVAL;
    }
    if (unlikely(!adap->algo)) {
        pr_err("i2c-core: Attempt to register adapter '%s' with "
               "no algo!\n", adap->name);
        return -EINVAL;
    }

    rt_mutex_init(&adap->bus_lock);
    mutex_init(&adap->userspace_clients_lock);
    INIT_LIST_HEAD(&adap->userspace_clients);

    /* Set default timeout to 1 second if not already set */
    if (adap->timeout == 0)
        adap->timeout = HZ;

    dev_set_name(&adap->dev, "i2c-%d", adap->nr);
    adap->dev.bus = &i2c_bus_type;
    adap->dev.type = &i2c_adapter_type;
    res = device_register(&adap->dev);
    if (res)
        goto out_list;

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

#ifdef CONFIG_I2C_COMPAT
    res = class_compat_create_link(i2c_adapter_compat_class, &adap->dev,
                       adap->dev.parent);
    if (res)
        dev_warn(&adap->dev,
             "Failed to create compatibility class link\n");
#endif

    /* create pre-declared device nodes */
    if (adap->nr < __i2c_first_dynamic_bus_num)
        i2c_scan_static_board_info(adap);

    /* Notify drivers */
    mutex_lock(&core_lock);
    bus_for_each_drv(&i2c_bus_type, NULL, adap, __process_new_adapter);
    mutex_unlock(&core_lock);

    return 0;

out_list:
    mutex_lock(&core_lock);
    idr_remove(&i2c_adapter_idr, adap->nr);
    mutex_unlock(&core_lock);
    return res;
}

int i2c_add_adapter(struct i2c_adapter *adapter)
{
    int id, res = 0;

retry:
    if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0)
        return -ENOMEM;

    mutex_lock(&core_lock);
    /* "above" here means "above or equal to", sigh */
    res = idr_get_new_above(&i2c_adapter_idr, adapter,
                __i2c_first_dynamic_bus_num, &id);
    mutex_unlock(&core_lock);

    if (res < 0) {
        if (res == -EAGAIN)
            goto retry;
        return res;
    }

    adapter->nr = id;
    return i2c_register_adapter(adapter);
}
EXPORT_SYMBOL(i2c_add_adapter);

int i2c_add_numbered_adapter(struct i2c_adapter *adap)
{
    int id;
    int status;

    if (adap->nr == -1) /* -1 means dynamically assign bus id */
        return i2c_add_adapter(adap);
    if (adap->nr & ~MAX_IDR_MASK)
        return -EINVAL;

retry:
    if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0)
        return -ENOMEM;

    mutex_lock(&core_lock);
    /* "above" here means "above or equal to", sigh;
     * we need the "equal to" result to force the result
     */
    status = idr_get_new_above(&i2c_adapter_idr, adap, adap->nr, &id);
    if (status == 0 && id != adap->nr) {
        status = -EBUSY;
        idr_remove(&i2c_adapter_idr, id);
    }
    mutex_unlock(&core_lock);
    if (status == -EAGAIN)
        goto retry;

    if (status == 0)
        status = i2c_register_adapter(adap);
    return status;
}
EXPORT_SYMBOL_GPL(i2c_add_numbered_adapter);

static int i2c_do_del_adapter(struct i2c_driver *driver,
                  struct i2c_adapter *adapter)
{
    struct i2c_client *client, *_n;
    int res;

    /* Remove the devices we created ourselves as the result of hardware
     * probing (using a driver's detect method) */
    list_for_each_entry_safe(client, _n, &driver->clients, detected) {
        if (client->adapter == adapter) {
            dev_dbg(&adapter->dev, "Removing %s at 0x%x\n",
                client->name, client->addr);
            list_del(&client->detected);
            i2c_unregister_device(client);
        }
    }

    if (!driver->detach_adapter)
        return 0;
    dev_warn(&adapter->dev, "%s: detach_adapter method is deprecated\n",
         driver->driver.name);
    res = driver->detach_adapter(adapter);
    if (res)
        dev_err(&adapter->dev, "detach_adapter failed (%d) "
            "for driver [%s]\n", res, driver->driver.name);
    return res;
}

static int __unregister_client(struct device *dev, void *dummy)
{
    struct i2c_client *client = i2c_verify_client(dev);
    if (client && strcmp(client->name, "dummy"))
        i2c_unregister_device(client);
    return 0;
}

static int __unregister_dummy(struct device *dev, void *dummy)
{
    struct i2c_client *client = i2c_verify_client(dev);
    if (client)
        i2c_unregister_device(client);
    return 0;
}

static int __process_removed_adapter(struct device_driver *d, void *data)
{
    return i2c_do_del_adapter(to_i2c_driver(d), data);
}

int i2c_del_adapter(struct i2c_adapter *adap)
{
    int res = 0;
    struct i2c_adapter *found;
    struct i2c_client *client, *next;

    /* First make sure that this adapter was ever added */
    mutex_lock(&core_lock);
    found = idr_find(&i2c_adapter_idr, adap->nr);
    mutex_unlock(&core_lock);
    if (found != adap) {
        pr_debug("i2c-core: attempting to delete unregistered "
             "adapter [%s]\n", adap->name);
        return -EINVAL;
    }

    /* Tell drivers about this removal */
    mutex_lock(&core_lock);
    res = bus_for_each_drv(&i2c_bus_type, NULL, adap,
                   __process_removed_adapter);
    mutex_unlock(&core_lock);
    if (res)
        return res;

    /* Remove devices instantiated from sysfs */
    mutex_lock_nested(&adap->userspace_clients_lock,
              i2c_adapter_depth(adap));
    list_for_each_entry_safe(client, next, &adap->userspace_clients,
                 detected) {
        dev_dbg(&adap->dev, "Removing %s at 0x%x\n", client->name,
            client->addr);
        list_del(&client->detected);
        i2c_unregister_device(client);
    }
    mutex_unlock(&adap->userspace_clients_lock);

    /* Detach any active clients. This can't fail, thus we do not
     * check the returned value. This is a two-pass process, because
     * we can't remove the dummy devices during the first pass: they
     * could have been instantiated by real devices wishing to clean
     * them up properly, so we give them a chance to do that first. */
    res = device_for_each_child(&adap->dev, NULL, __unregister_client);
    res = device_for_each_child(&adap->dev, NULL, __unregister_dummy);

#ifdef CONFIG_I2C_COMPAT
    class_compat_remove_link(i2c_adapter_compat_class, &adap->dev,
                 adap->dev.parent);
#endif

    /* device name is gone after device_unregister */
    dev_dbg(&adap->dev, "adapter [%s] unregistered\n", adap->name);

    /* clean up the sysfs representation */
    init_completion(&adap->dev_released);
    device_unregister(&adap->dev);

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

    /* free bus id */
    mutex_lock(&core_lock);
    idr_remove(&i2c_adapter_idr, adap->nr);
    mutex_unlock(&core_lock);

    /* Clear the device structure in case this adapter is ever going to be
       added again */
    memset(&adap->dev, 0, sizeof(adap->dev));

    return 0;
}
EXPORT_SYMBOL(i2c_del_adapter);


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

int i2c_for_each_dev(void *data, int (*fn)(struct device *, void *))
{
    int res;

    mutex_lock(&core_lock);
    res = bus_for_each_dev(&i2c_bus_type, NULL, data, fn);
    mutex_unlock(&core_lock);

    return res;
}
EXPORT_SYMBOL_GPL(i2c_for_each_dev);

static int __process_new_driver(struct device *dev, void *data)
{
    if (dev->type != &i2c_adapter_type)
        return 0;
    return i2c_do_add_adapter(data, to_i2c_adapter(dev));
}

/*
 * An i2c_driver is used with one or more i2c_client (device) nodes to access
 * i2c slave chips, on a bus instance associated with some i2c_adapter.
 */

int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
{
    int res;

    /* Can't register until after driver model init */
    if (unlikely(WARN_ON(!i2c_bus_type.p)))
        return -EAGAIN;

    /* add the driver to the list of i2c drivers in the driver core */
    driver->driver.owner = owner;
    driver->driver.bus = &i2c_bus_type;

    /* When registration returns, the driver core
     * will have called probe() for all matching-but-unbound devices.
     */
    res = driver_register(&driver->driver);
    if (res)
        return res;

    /* Drivers should switch to dev_pm_ops instead. */
    if (driver->suspend)
        pr_warn("i2c-core: driver [%s] using legacy suspend method\n",
            driver->driver.name);
    if (driver->resume)
        pr_warn("i2c-core: driver [%s] using legacy resume method\n",
            driver->driver.name);

    pr_debug("i2c-core: driver [%s] registered\n", driver->driver.name);

    INIT_LIST_HEAD(&driver->clients);
    /* Walk the adapters that are already present */
    i2c_for_each_dev(driver, __process_new_driver);

    return 0;
}
EXPORT_SYMBOL(i2c_register_driver);

static int __process_removed_driver(struct device *dev, void *data)
{
    if (dev->type != &i2c_adapter_type)
        return 0;
    return i2c_do_del_adapter(data, to_i2c_adapter(dev));
}

void i2c_del_driver(struct i2c_driver *driver)
{
    i2c_for_each_dev(driver, __process_removed_driver);

    driver_unregister(&driver->driver);
    pr_debug("i2c-core: driver [%s] unregistered\n", driver->driver.name);
}
EXPORT_SYMBOL(i2c_del_driver);

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

struct i2c_client *i2c_use_client(struct i2c_client *client)
{
    if (client && get_device(&client->dev))
        return client;
    return NULL;
}
EXPORT_SYMBOL(i2c_use_client);

void i2c_release_client(struct i2c_client *client)
{
    if (client)
        put_device(&client->dev);
}
EXPORT_SYMBOL(i2c_release_client);

struct i2c_cmd_arg {
    unsigned    cmd;
    void        *arg;
};

static int i2c_cmd(struct device *dev, void *_arg)
{
    struct i2c_client   *client = i2c_verify_client(dev);
    struct i2c_cmd_arg  *arg = _arg;

    if (client && client->driver && client->driver->command)
        client->driver->command(client, arg->cmd, arg->arg);
    return 0;
}

void i2c_clients_command(struct i2c_adapter *adap, unsigned int cmd, void *arg)
{
    struct i2c_cmd_arg  cmd_arg;

    cmd_arg.cmd = cmd;
    cmd_arg.arg = arg;
    device_for_each_child(&adap->dev, &cmd_arg, i2c_cmd);
}
EXPORT_SYMBOL(i2c_clients_command);

static int __init i2c_init(void)
{
    int retval;

    retval = bus_register(&i2c_bus_type);
    if (retval)
        return retval;
#ifdef CONFIG_I2C_COMPAT
    i2c_adapter_compat_class = class_compat_register("i2c-adapter");
    if (!i2c_adapter_compat_class) {
        retval = -ENOMEM;
        goto bus_err;
    }
#endif
    retval = i2c_add_driver(&dummy_driver);
    if (retval)
        goto class_err;
    return 0;

class_err:
#ifdef CONFIG_I2C_COMPAT
    class_compat_unregister(i2c_adapter_compat_class);
bus_err:
#endif
    bus_unregister(&i2c_bus_type);
    return retval;
}

static void __exit i2c_exit(void)
{
    i2c_del_driver(&dummy_driver);
#ifdef CONFIG_I2C_COMPAT
    class_compat_unregister(i2c_adapter_compat_class);
#endif
    bus_unregister(&i2c_bus_type);
}

/* We must initialize early, because some subsystems register i2c drivers
 * in subsys_initcall() code, but are linked (and initialized) before i2c.
 */
postcore_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)
{
    unsigned long orig_jiffies;
    int ret, try;

    /* Retry automatically on arbitration loss */
    orig_jiffies = jiffies;
    for (ret = 0, try = 0; try <= adap->retries; try++) {
        ret = adap->algo->master_xfer(adap, msgs, num);
        if (ret != -EAGAIN)
            break;
        if (time_after(jiffies, orig_jiffies + adap->timeout))
            break;
    }

    return ret;
}
EXPORT_SYMBOL(__i2c_transfer);

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

    /* REVISIT the fault reporting model here is weak:
     *
     *  - When we get an error after receiving N bytes from a slave,
     *    there is no way to report "N".
     *
     *  - When we get a NAK after transmitting N bytes to a slave,
     *    there is no way to report "N" ... or to let the master
     *    continue executing the rest of this combined message, if
     *    that's the appropriate response.
     *
     *  - When for example "num" is two and we successfully complete
     *    the first message but get an error part way through the
     *    second, it's unclear whether that should be reported as
     *    one (discarding status on the second message) or errno
     *    (discarding status on the first one).
     */

    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%s\n", ret, (msgs[ret].flags & I2C_M_RD)
                ? 'R' : 'W', msgs[ret].addr, msgs[ret].len,
                (msgs[ret].flags & I2C_M_RECV_LEN) ? "+" : "");
        }
#endif

        if (in_atomic() || irqs_disabled()) {
            ret = i2c_trylock_adapter(adap);
            if (!ret)
                /* I2C activity is ongoing. */
                return -EAGAIN;
        } else {
            i2c_lock_adapter(adap);
        }

        ret = __i2c_transfer(adap, msgs, num);
        i2c_unlock_adapter(adap);

        return ret;
    } else {
        dev_dbg(&adap->dev, "I2C level transfers not supported\n");
        return -EOPNOTSUPP;
    }
}
EXPORT_SYMBOL(i2c_transfer);

int i2c_master_send(const 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;
}
EXPORT_SYMBOL(i2c_master_send);

int i2c_master_recv(const 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 received), return #bytes received,
     * else error code.
     */
    return (ret == 1) ? count : ret;
}
EXPORT_SYMBOL(i2c_master_recv);

/* ----------------------------------------------------
 * the i2c address scanning function
 * Will not work for 10-bit addresses!
 * ----------------------------------------------------
 */

/*
 * Legacy default probe function, mostly relevant for SMBus. The default
 * probe method is a quick write, but it is known to corrupt the 24RF08
 * EEPROMs due to a state machine bug, and could also irreversibly
 * write-protect some EEPROMs, so for address ranges 0x30-0x37 and 0x50-0x5f,
 * we use a short byte read instead. Also, some bus drivers don't implement
 * quick write, so we fallback to a byte read in that case too.
 * On x86, there is another special case for FSC hardware monitoring chips,
 * which want regular byte reads (address 0x73.) Fortunately, these are the
 * only known chips using this I2C address on PC hardware.
 * Returns 1 if probe succeeded, 0 if not.
 */
static int i2c_default_probe(struct i2c_adapter *adap, unsigned short addr)
{
    int err;
    union i2c_smbus_data dummy;

#ifdef CONFIG_X86
    if (addr == 0x73 && (adap->class & I2C_CLASS_HWMON)
     && i2c_check_functionality(adap, I2C_FUNC_SMBUS_READ_BYTE_DATA))
        err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
                     I2C_SMBUS_BYTE_DATA, &dummy);
    else
#endif
    if (!((addr & ~0x07) == 0x30 || (addr & ~0x0f) == 0x50)
     && i2c_check_functionality(adap, I2C_FUNC_SMBUS_QUICK))
        err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_WRITE, 0,
                     I2C_SMBUS_QUICK, NULL);
    else if (i2c_check_functionality(adap, I2C_FUNC_SMBUS_READ_BYTE))
        err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
                     I2C_SMBUS_BYTE, &dummy);
    else {
        dev_warn(&adap->dev, "No suitable probing method supported\n");
        err = -EOPNOTSUPP;
    }

    return err >= 0;
}

static int i2c_detect_address(struct i2c_client *temp_client,
                  struct i2c_driver *driver)
{
    struct i2c_board_info info;
    struct i2c_adapter *adapter = temp_client->adapter;
    int addr = temp_client->addr;
    int err;

    /* Make sure the address is valid */
    err = i2c_check_addr_validity(addr);
    if (err) {
        dev_warn(&adapter->dev, "Invalid probe address 0x%02x\n",
             addr);
        return err;
    }

    /* Skip if already in use */
    if (i2c_check_addr_busy(adapter, addr))
        return 0;

    /* Make sure there is something at this address */
    if (!i2c_default_probe(adapter, addr))
        return 0;

    /* Finally call the custom detection function */
    memset(&info, 0, sizeof(struct i2c_board_info));
    info.addr = addr;
    err = driver->detect(temp_client, &info);
    if (err) {
        /* -ENODEV is returned if the detection fails. We catch it
           here as this isn't an error. */
        return err == -ENODEV ? 0 : err;
    }

    /* Consistency check */
    if (info.type[0] == '\0') {
        dev_err(&adapter->dev, "%s detection function provided "
            "no name for 0x%x\n", driver->driver.name,
            addr);
    } else {
        struct i2c_client *client;

        /* Detection succeeded, instantiate the device */
        dev_dbg(&adapter->dev, "Creating %s at 0x%02x\n",
            info.type, info.addr);
        client = i2c_new_device(adapter, &info);
        if (client)
            list_add_tail(&client->detected, &driver->clients);
        else
            dev_err(&adapter->dev, "Failed creating %s at 0x%02x\n",
                info.type, info.addr);
    }
    return 0;
}

static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver)
{
    const unsigned short *address_list;
    struct i2c_client *temp_client;
    int i, err = 0;
    int adap_id = i2c_adapter_id(adapter);

    address_list = driver->address_list;
    if (!driver->detect || !address_list)
        return 0;

    /* Stop here if the classes do not match */
    if (!(adapter->class & driver->class))
        return 0;

    /* Set up a temporary client to help detect callback */
    temp_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
    if (!temp_client)
        return -ENOMEM;
    temp_client->adapter = adapter;

    for (i = 0; address_list[i] != I2C_CLIENT_END; i += 1) {
        dev_dbg(&adapter->dev, "found normal entry for adapter %d, "
            "addr 0x%02x\n", adap_id, address_list[i]);
        temp_client->addr = address_list[i];
        err = i2c_detect_address(temp_client, driver);
        if (unlikely(err))
            break;
    }

    kfree(temp_client);
    return err;
}

int i2c_probe_func_quick_read(struct i2c_adapter *adap, unsigned short addr)
{
    return i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
                  I2C_SMBUS_QUICK, NULL) >= 0;
}
EXPORT_SYMBOL_GPL(i2c_probe_func_quick_read);

struct i2c_client *
i2c_new_probed_device(struct i2c_adapter *adap,
              struct i2c_board_info *info,
              unsigned short const *addr_list,
              int (*probe)(struct i2c_adapter *, unsigned short addr))
{
    int i;

    if (!probe)
        probe = i2c_default_probe;

    for (i = 0; addr_list[i] != I2C_CLIENT_END; i++) {
        /* Check address validity */
        if (i2c_check_addr_validity(addr_list[i]) < 0) {
            dev_warn(&adap->dev, "Invalid 7-bit address "
                 "0x%02x\n", addr_list[i]);
            continue;
        }

        /* Check address availability */
        if (i2c_check_addr_busy(adap, addr_list[i])) {
            dev_dbg(&adap->dev, "Address 0x%02x already in "
                "use, not probing\n", addr_list[i]);
            continue;
        }

        /* Test address responsiveness */
        if (probe(adap, addr_list[i]))
            break;
    }

    if (addr_list[i] == I2C_CLIENT_END) {
        dev_dbg(&adap->dev, "Probing failed, no device found\n");
        return NULL;
    }

    info->addr = addr_list[i];
    return i2c_new_device(adap, info);
}
EXPORT_SYMBOL_GPL(i2c_new_probed_device);

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

    mutex_lock(&core_lock);
    adapter = idr_find(&i2c_adapter_idr, nr);
    if (adapter && !try_module_get(adapter->owner))
        adapter = NULL;

    mutex_unlock(&core_lock);
    return adapter;
}
EXPORT_SYMBOL(i2c_get_adapter);

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

/* 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);
}

/* Incremental CRC8 over count bytes in the array pointed to by p */
static u8 i2c_smbus_pec(u8 crc, u8 *p, size_t count)
{
    int i;

    for (i = 0; i < count; i++)
        crc = crc8((crc ^ p[i]) << 8);
    return crc;
}

/* Assume a 7-bit address, which is reasonable for SMBus */
static u8 i2c_smbus_msg_pec(u8 pec, struct i2c_msg *msg)
{
    /* The address will be sent first */
    u8 addr = (msg->addr << 1) | !!(msg->flags & I2C_M_RD);
    pec = i2c_smbus_pec(pec, &addr, 1);

    /* The data buffer follows */
    return i2c_smbus_pec(pec, msg->buf, msg->len);
}

/* Used for write only transactions */
static inline void i2c_smbus_add_pec(struct i2c_msg *msg)
{
    msg->buf[msg->len] = i2c_smbus_msg_pec(0, msg);
    msg->len++;
}

/* Return <0 on CRC error
   If there was a write before this read (most cases) we need to take the
   partial CRC from the write part into account.
   Note that this function does modify the message (we need to decrease the
   message length to hide the CRC byte from the caller). */
static int i2c_smbus_check_pec(u8 cpec, struct i2c_msg *msg)
{
    u8 rpec = msg->buf[--msg->len];
    cpec = i2c_smbus_msg_pec(cpec, msg);

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

s32 i2c_smbus_read_byte(const struct i2c_client *client)
{
    union i2c_smbus_data data;
    int status;

    status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
                I2C_SMBUS_READ, 0,
                I2C_SMBUS_BYTE, &data);
    return (status < 0) ? status : data.byte;
}
EXPORT_SYMBOL(i2c_smbus_read_byte);

s32 i2c_smbus_write_byte(const struct i2c_client *client, u8 value)
{
    return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
                          I2C_SMBUS_WRITE, value, I2C_SMBUS_BYTE, NULL);
}
EXPORT_SYMBOL(i2c_smbus_write_byte);

s32 i2c_smbus_read_byte_data(const struct i2c_client *client, u8 command)
{
    union i2c_smbus_data data;
    int status;

    status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
                I2C_SMBUS_READ, command,
                I2C_SMBUS_BYTE_DATA, &data);
    return (status < 0) ? status : data.byte;
}
EXPORT_SYMBOL(i2c_smbus_read_byte_data);

s32 i2c_smbus_write_byte_data(const 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);
}
EXPORT_SYMBOL(i2c_smbus_write_byte_data);

s32 i2c_smbus_read_word_data(const struct i2c_client *client, u8 command)
{
    union i2c_smbus_data data;
    int status;

    status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
                I2C_SMBUS_READ, command,
                I2C_SMBUS_WORD_DATA, &data);
    return (status < 0) ? status : data.word;
}
EXPORT_SYMBOL(i2c_smbus_read_word_data);

s32 i2c_smbus_write_word_data(const 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);
}
EXPORT_SYMBOL(i2c_smbus_write_word_data);

s32 i2c_smbus_process_call(const struct i2c_client *client, u8 command,
               u16 value)
{
    union i2c_smbus_data data;
    int status;
    data.word = value;

    status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
                I2C_SMBUS_WRITE, command,
                I2C_SMBUS_PROC_CALL, &data);
    return (status < 0) ? status : data.word;
}
EXPORT_SYMBOL(i2c_smbus_process_call);

s32 i2c_smbus_read_block_data(const struct i2c_client *client, u8 command,
                  u8 *values)
{
    union i2c_smbus_data data;
    int status;

    status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
                I2C_SMBUS_READ, command,
                I2C_SMBUS_BLOCK_DATA, &data);
    if (status)
        return status;

    memcpy(values, &data.block[1], data.block[0]);
    return data.block[0];
}
EXPORT_SYMBOL(i2c_smbus_read_block_data);

s32 i2c_smbus_write_block_data(const struct i2c_client *client, u8 command,
                   u8 length, const u8 *values)
{
    union i2c_smbus_data data;

    if (length > I2C_SMBUS_BLOCK_MAX)
        length = I2C_SMBUS_BLOCK_MAX;
    data.block[0] = length;
    memcpy(&data.block[1], values, length);
    return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
                  I2C_SMBUS_WRITE, command,
                  I2C_SMBUS_BLOCK_DATA, &data);
}
EXPORT_SYMBOL(i2c_smbus_write_block_data);

/* Returns the number of read bytes */
s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client, u8 command,
                  u8 length, u8 *values)
{
    union i2c_smbus_data data;
    int status;

    if (length > I2C_SMBUS_BLOCK_MAX)
        length = I2C_SMBUS_BLOCK_MAX;
    data.block[0] = length;
    status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
                I2C_SMBUS_READ, command,
                I2C_SMBUS_I2C_BLOCK_DATA, &data);
    if (status < 0)
        return status;

    memcpy(values, &data.block[1], data.block[0]);
    return data.block[0];
}
EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data);

s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client, u8 command,
                   u8 length, const u8 *values)
{
    union i2c_smbus_data data;

    if (length > I2C_SMBUS_BLOCK_MAX)
        length = I2C_SMBUS_BLOCK_MAX;
    data.block[0] = length;
    memcpy(data.block + 1, values, length);
    return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
                  I2C_SMBUS_WRITE, command,
                  I2C_SMBUS_I2C_BLOCK_DATA, &data);
}
EXPORT_SYMBOL(i2c_smbus_write_i2c_block_data);

/* 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[I2C_SMBUS_BLOCK_MAX+3];
    unsigned char msgbuf1[I2C_SMBUS_BLOCK_MAX+2];
    int num = read_write == I2C_SMBUS_READ ? 2 : 1;
    int i;
    u8 partial_pec = 0;
    int status;
    struct i2c_msg msg[2] = {
        {
            .addr = addr,
            .flags = flags,
            .len = 1,
            .buf = msgbuf0,
        }, {
            .addr = addr,
            .flags = flags | I2C_M_RD,
            .len = 0,
            .buf = msgbuf1,
        },
    };

    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;
        }
        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;
        break;
    case I2C_SMBUS_BLOCK_DATA:
        if (read_write == I2C_SMBUS_READ) {
            msg[1].flags |= I2C_M_RECV_LEN;
            msg[1].len = 1; /* block length will be added by
                       the underlying bus driver */
        } else {
            msg[0].len = data->block[0] + 2;
            if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 2) {
                dev_err(&adapter->dev,
                    "Invalid block write size %d\n",
                    data->block[0]);
                return -EINVAL;
            }
            for (i = 1; i < msg[0].len; i++)
                msgbuf0[i] = data->block[i-1];
        }
        break;
    case I2C_SMBUS_BLOCK_PROC_CALL:
        num = 2; /* Another special case */
        read_write = I2C_SMBUS_READ;
        if (data->block[0] > I2C_SMBUS_BLOCK_MAX) {
            dev_err(&adapter->dev,
                "Invalid block write size %d\n",
                data->block[0]);
            return -EINVAL;
        }
        msg[0].len = data->block[0] + 2;
        for (i = 1; i < msg[0].len; i++)
            msgbuf0[i] = data->block[i-1];
        msg[1].flags |= I2C_M_RECV_LEN;
        msg[1].len = 1; /* block length will be added by
                   the underlying bus driver */
        break;
    case I2C_SMBUS_I2C_BLOCK_DATA:
        if (read_write == I2C_SMBUS_READ) {
            msg[1].len = data->block[0];
        } else {
            msg[0].len = data->block[0] + 1;
            if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 1) {
                dev_err(&adapter->dev,
                    "Invalid block write size %d\n",
                    data->block[0]);
                return -EINVAL;
            }
            for (i = 1; i <= data->block[0]; i++)
                msgbuf0[i] = data->block[i];
        }
        break;
    default:
        dev_err(&adapter->dev, "Unsupported transaction %d\n", size);
        return -EOPNOTSUPP;
    }

    i = ((flags & I2C_CLIENT_PEC) && size != I2C_SMBUS_QUICK
                      && size != I2C_SMBUS_I2C_BLOCK_DATA);
    if (i) {
        /* Compute PEC if first message is a write */
        if (!(msg[0].flags & I2C_M_RD)) {
            if (num == 1) /* Write only */
                i2c_smbus_add_pec(&msg[0]);
            else /* Write followed by read */
                partial_pec = i2c_smbus_msg_pec(0, &msg[0]);
        }
        /* Ask for PEC if last message is a read */
        if (msg[num-1].flags & I2C_M_RD)
            msg[num-1].len++;
    }

    status = i2c_transfer(adapter, msg, num);
    if (status < 0)
        return status;

    /* Check PEC if last message is a read */
    if (i && (msg[num-1].flags & I2C_M_RD)) {
        status = i2c_smbus_check_pec(partial_pec, &msg[num-1]);
        if (status < 0)
            return status;
    }

    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:
            for (i = 0; i < data->block[0]; i++)
                data->block[i+1] = msgbuf1[i];
            break;
        case I2C_SMBUS_BLOCK_DATA:
        case I2C_SMBUS_BLOCK_PROC_CALL:
            for (i = 0; i < msgbuf1[0] + 1; i++)
                data->block[i] = msgbuf1[i];
            break;
        }
    return 0;
}

s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
           char read_write, u8 command, int protocol,
           union i2c_smbus_data *data)
{
    unsigned long orig_jiffies;
    int try;
    s32 res;

    flags &= I2C_M_TEN | I2C_CLIENT_PEC | I2C_CLIENT_SCCB;

    if (adapter->algo->smbus_xfer) {
        i2c_lock_adapter(adapter);

        /* Retry automatically on arbitration loss */
        orig_jiffies = jiffies;
        for (res = 0, try = 0; try <= adapter->retries; try++) {
            res = adapter->algo->smbus_xfer(adapter, addr, flags,
                            read_write, command,
                            protocol, data);
            if (res != -EAGAIN)
                break;
            if (time_after(jiffies,
                       orig_jiffies + adapter->timeout))
                break;
        }
        i2c_unlock_adapter(adapter);

        if (res != -EOPNOTSUPP || !adapter->algo->master_xfer)
            return res;
        /*
         * Fall back to i2c_smbus_xfer_emulated if the adapter doesn't
         * implement native support for the SMBus operation.
         */
    }

    return i2c_smbus_xfer_emulated(adapter, addr, flags, read_write,
                       command, protocol, data);
}
EXPORT_SYMBOL(i2c_smbus_xfer);

MODULE_AUTHOR("Simon G. Vogl <[email protected]>");
MODULE_DESCRIPTION("I2C-Bus main module");
MODULE_LICENSE("GPL");