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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);