/*
 * 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.
 * Copyright (C) 2004 Jean Delvare <jdelvare@suse.de>
 *
 * 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.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/jiffies.h>
#include <linux/i2c.h>
#include <linux/mutex.h>

/* Addresses to scan */
static const unsigned short normal_i2c[] = { 0x50, 0x51, 0x52, 0x53, 0x54,
                                        0x55, 0x56, 0x57, I2C_CLIENT_END };


/* 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 mutex update_lock;
        u8 valid;                       /* bitfield, bit!=0 if slice is valid */
        unsigned long last_updated[8];  /* In jiffies, 8 slices */
        u8 data[EEPROM_SIZE];           /* Register values */
        enum eeprom_nature nature;
};


static void eeprom_update_client(struct i2c_client *client, u8 slice)
{
        struct eeprom_data *data = i2c_get_clientdata(client);
        int i;

        mutex_lock(&data->update_lock);

        if (!(data->valid & (1 << slice)) ||
            time_after(jiffies, data->last_updated[slice] + 300 * HZ)) {
                dev_dbg(&client->dev, "Starting eeprom update, slice %u\n", slice);

                if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
                        for (i = slice << 5; i < (slice + 1) << 5; i += 32)
                                if (i2c_smbus_read_i2c_block_data(client, i,
                                                        32, data->data + i)
                                                        != 32)
                                        goto exit;
                } else {
                        for (i = slice << 5; i < (slice + 1) << 5; i += 2) {
                                int word = i2c_smbus_read_word_data(client, i);
                                if (word < 0)
                                        goto exit;
                                data->data[i] = word & 0xff;
                                data->data[i + 1] = word >> 8;
                        }
                }
                data->last_updated[slice] = jiffies;
                data->valid |= (1 << slice);
        }
exit:
        mutex_unlock(&data->update_lock);
}

static ssize_t eeprom_read(struct file *filp, struct kobject *kobj,
                           struct bin_attribute *bin_attr,
                           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);
        u8 slice;

        if (off > EEPROM_SIZE)
                return 0;
        if (off + count > EEPROM_SIZE)
                count = EEPROM_SIZE - off;

        /* Only refresh slices which contain requested bytes */
        for (slice = off >> 5; slice <= (off + count - 1) >> 5; slice++)
                eeprom_update_client(client, slice);

        /* Hide Vaio private settings to regular users:
           - BIOS passwords: bytes 0x00 to 0x0f
           - UUID: bytes 0x10 to 0x1f
           - Serial number: 0xc0 to 0xdf */
        if (data->nature == VAIO && !capable(CAP_SYS_ADMIN)) {
                int i;

                for (i = 0; i < count; i++) {
                        if ((off + i <= 0x1f) ||
                            (off + i >= 0xc0 && off + i <= 0xdf))
                                buf[i] = 0;
                        else
                                buf[i] = data->data[off + i];
                }
        } else {
                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,
};

/* Return 0 if detection is successful, -ENODEV otherwise */
static int eeprom_detect(struct i2c_client *client, struct i2c_board_info *info)
{
        struct i2c_adapter *adapter = client->adapter;

        /* EDID EEPROMs are often 24C00 EEPROMs, which answer to all
           addresses 0x50-0x57, but we only care about 0x50. So decline
           attaching to addresses >= 0x51 on DDC buses */
        if (!(adapter->class & I2C_CLASS_SPD) && client->addr >= 0x51)
                return -ENODEV;

        /* There are four ways we can read the EEPROM data:
           (1) I2C block reads (faster, but unsupported by most adapters)
           (2) Word reads (128% overhead)
           (3) Consecutive byte reads (88% overhead, unsafe)
           (4) Regular byte data reads (265% overhead)
           The third and fourth methods are not implemented by this driver
           because all known adapters support one of the first two. */
        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_WORD_DATA)
         && !i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK))
                return -ENODEV;

        strlcpy(info->type, "eeprom", I2C_NAME_SIZE);

        return 0;
}

static int eeprom_probe(struct i2c_client *client,
                        const struct i2c_device_id *id)
{
        struct i2c_adapter *adapter = client->adapter;
        struct eeprom_data *data;

        data = devm_kzalloc(&client->dev, sizeof(struct eeprom_data),
                            GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        memset(data->data, 0xff, EEPROM_SIZE);
        i2c_set_clientdata(client, data);
        mutex_init(&data->update_lock);
        data->nature = UNKNOWN;

        /* Detect the Vaio nature of EEPROMs.
           We use the "PCG-" or "VGN-" prefix as the signature. */
        if (client->addr == 0x57
         && i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
                char name[4];

                name[0] = i2c_smbus_read_byte_data(client, 0x80);
                name[1] = i2c_smbus_read_byte_data(client, 0x81);
                name[2] = i2c_smbus_read_byte_data(client, 0x82);
                name[3] = i2c_smbus_read_byte_data(client, 0x83);

                if (!memcmp(name, "PCG-", 4) || !memcmp(name, "VGN-", 4)) {
                        dev_info(&client->dev, "Vaio EEPROM detected, "
                                 "enabling privacy protection\n");
                        data->nature = VAIO;
                }
        }

        /* create the sysfs eeprom file */
        return sysfs_create_bin_file(&client->dev.kobj, &eeprom_attr);
}

static int eeprom_remove(struct i2c_client *client)
{
        sysfs_remove_bin_file(&client->dev.kobj, &eeprom_attr);

        return 0;
}

static const struct i2c_device_id eeprom_id[] = {
        { "eeprom", 0 },
        { }
};

static struct i2c_driver eeprom_driver = {
        .driver = {
                .name   = "eeprom",
        },
        .probe          = eeprom_probe,
        .remove         = eeprom_remove,
        .id_table       = eeprom_id,

        .class          = I2C_CLASS_DDC | I2C_CLASS_SPD,
        .detect         = eeprom_detect,
        .address_list   = normal_i2c,
};

module_i2c_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");