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/*

    eeprom.c - Part of lm_sensors, Linux kernel modules for hardware

               monitoring

    Copyright (C) 1998, 1999  Frodo Looijaard <frodol@dds.nl> and

                               Philip Edelbrock <phil@netroedge.com>

    Copyright (C) 2003 Greg Kroah-Hartman <greg@kroah.com>

    Copyright (C) 2003 IBM Corp.

    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.

*/

/* #define DEBUG */

#include <linux/kernel.h>

#include <linux/init.h>

#include <linux/module.h>

#include <linux/slab.h>

#include <linux/i2c.h>

#include <linux/i2c-sensor.h>

/* Addresses to scan */

static unsigned short normal_i2c[] = { I2C_CLIENT_END };

static unsigned short normal_i2c_range[] = { 0x50, 0x57, I2C_CLIENT_END };

static unsigned int normal_isa[] = { I2C_CLIENT_ISA_END };

static unsigned int normal_isa_range[] = { I2C_CLIENT_ISA_END };

/* Insmod parameters */

SENSORS_INSMOD_1(eeprom);

static int checksum = 0;

MODULE_PARM(checksum, "i");

MODULE_PARM_DESC(checksum, "Only accept eeproms whose checksum is correct");

/* EEPROM registers */

#define EEPROM_REG_CHECKSUM     0x3f

/* Size of EEPROM in bytes */

#define EEPROM_SIZE             256

/* possible types of eeprom devices */

enum eeprom_nature {

        UNKNOWN,

        VAIO,

};

/* Each client has this additional data */

struct eeprom_data {

        struct semaphore update_lock;

        char valid;                     /* !=0 if following fields are valid */

        unsigned long last_updated;     /* In jiffies */

        u8 data[EEPROM_SIZE];           /* Register values */

};

static int eeprom_attach_adapter(struct i2c_adapter *adapter);

static int eeprom_detect(struct i2c_adapter *adapter, int address, int kind);

static int eeprom_detach_client(struct i2c_client *client);

/* This is the driver that will be inserted */

static struct i2c_driver eeprom_driver = {

        .owner          = THIS_MODULE,

        .name           = "eeprom",

        .id             = I2C_DRIVERID_EEPROM,

        .flags          = I2C_DF_NOTIFY,

        .attach_adapter = eeprom_attach_adapter,

        .detach_client  = eeprom_detach_client,

};

static int eeprom_id = 0;

static void eeprom_update_client(struct i2c_client *client)

{

        struct eeprom_data *data = i2c_get_clientdata(client);

        int i, j;

        down(&data->update_lock);

        if ((jiffies - data->last_updated > 300 * HZ) |

            (jiffies < data->last_updated) || !data->valid) {

                dev_dbg(&client->dev, "Starting eeprom update\n");

                if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {

                        for (i=0; i < EEPROM_SIZE; i += I2C_SMBUS_I2C_BLOCK_MAX)

                                if (i2c_smbus_read_i2c_block_data(client, i, data->data + i) != I2C_SMBUS_I2C_BLOCK_MAX)

                                        goto exit;

                } else {

                        if (i2c_smbus_write_byte(client, 0)) {

                                dev_dbg(&client->dev, "eeprom read start has failed!\n");

                                goto exit;

                        }

                        for (i = 0; i < EEPROM_SIZE; i++) {

                                j = i2c_smbus_read_byte(client);

                                if (j < 0)

                                        goto exit;

                                data->data[i] = (u8) j;

                        }

                }

                data->last_updated = jiffies;

                data->valid = 1;

        }

exit:

        up(&data->update_lock);

}

static ssize_t eeprom_read(struct kobject *kobj, char *buf, loff_t off, size_t count)

{

        struct i2c_client *client = to_i2c_client(container_of(kobj, struct device, kobj));

        struct eeprom_data *data = i2c_get_clientdata(client);

        eeprom_update_client(client);

        if (off > EEPROM_SIZE)

                return 0;

        if (off + count > EEPROM_SIZE)

                count = EEPROM_SIZE - off;

        memcpy(buf, &data->data[off], count);

        return count;

}

static struct bin_attribute eeprom_attr = {

        .attr = {

                .name = "eeprom",

                .mode = S_IRUGO,

        },

        .size = EEPROM_SIZE,

        .read = eeprom_read,

};

static int eeprom_attach_adapter(struct i2c_adapter *adapter)

{

        return i2c_detect(adapter, &addr_data, eeprom_detect);

}

/* This function is called by i2c_detect */

int eeprom_detect(struct i2c_adapter *adapter, int address, int kind)

{

        int i, cs;

        struct i2c_client *new_client;

        struct eeprom_data *data;

        enum eeprom_nature nature = UNKNOWN;

        int err = 0;

        /* Make sure we aren't probing the ISA bus!! This is just a safety check

           at this moment; i2c_detect really won't call us. */

#ifdef DEBUG

        if (i2c_is_isa_adapter(adapter)) {

                dev_dbg(&adapter->dev, " eeprom_detect called for an ISA bus adapter?!?\n");

                return 0;

        }

#endif

        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))

                goto exit;

        /* OK. For now, we presume we have a valid client. We now create the

           client structure, even though we cannot fill it completely yet.

           But it allows us to access eeprom_{read,write}_value. */

        if (!(new_client = kmalloc(sizeof(struct i2c_client) +

                                   sizeof(struct eeprom_data),

                                   GFP_KERNEL))) {

                err = -ENOMEM;

                goto exit;

        }

        memset(new_client, 0x00, sizeof(struct i2c_client) +

                                 sizeof(struct eeprom_data));

        data = (struct eeprom_data *) (new_client + 1);

        memset(data, 0xff, EEPROM_SIZE);

        i2c_set_clientdata(new_client, data);

        new_client->addr = address;

        new_client->adapter = adapter;

        new_client->driver = &eeprom_driver;

        new_client->flags = 0;

        /* Now, we do the remaining detection. It is not there, unless you force

           the checksum to work out. */

        if (checksum) {

                /* prevent 24RF08 corruption */

                i2c_smbus_write_quick(new_client, 0);

                cs = 0;

                for (i = 0; i <= 0x3e; i++)

                        cs += i2c_smbus_read_byte_data(new_client, i);

                cs &= 0xff;

                if (i2c_smbus_read_byte_data (new_client, EEPROM_REG_CHECKSUM) != cs)

                        goto exit_kfree;

        }

        /* Detect the Vaio nature of EEPROMs.

           We use the "PCG-" prefix as the signature. */

        if (address == 0x57) {

                if (i2c_smbus_read_byte_data(new_client, 0x80) == 'P' &&

                    i2c_smbus_read_byte_data(new_client, 0x81) == 'C' &&

                    i2c_smbus_read_byte_data(new_client, 0x82) == 'G' &&

                    i2c_smbus_read_byte_data(new_client, 0x83) == '-')

                        nature = VAIO;

        }

        /* If this is a VIAO, then we only allow root to read from this file,

           as BIOS passwords can be present here in plaintext */

        switch (nature) {

        case VAIO:

                eeprom_attr.attr.mode = S_IRUSR;

                break;

        default:

                eeprom_attr.attr.mode = S_IRUGO;

        }

        /* Fill in the remaining client fields */

        strncpy(new_client->name, "eeprom", I2C_NAME_SIZE);

        new_client->id = eeprom_id++;

        data->valid = 0;

        init_MUTEX(&data->update_lock);

        /* Tell the I2C layer a new client has arrived */

        if ((err = i2c_attach_client(new_client)))

                goto exit_kfree;

        /* create the sysfs eeprom file */

        sysfs_create_bin_file(&new_client->dev.kobj, &eeprom_attr);

        return 0;

exit_kfree:

        kfree(new_client);

exit:

        return err;

}

static int eeprom_detach_client(struct i2c_client *client)

{

        int err;

        err = i2c_detach_client(client);

        if (err) {

                dev_err(&client->dev, "Client deregistration failed, client not detached.\n");

                return err;

        }

        kfree(client);

        return 0;

}

static int __init eeprom_init(void)

{

        return i2c_add_driver(&eeprom_driver);

}

static void __exit eeprom_exit(void)

{

        i2c_del_driver(&eeprom_driver);

}

MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl> and "

                "Philip Edelbrock <phil@netroedge.com> and "

                "Greg Kroah-Hartman <greg@kroah.com>");

MODULE_DESCRIPTION("I2C EEPROM driver");

MODULE_LICENSE("GPL");

module_init(eeprom_init);

module_exit(eeprom_exit);