eeprom.c

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/*
 * Copyright (C) 1998, 1999  Frodo Looijaard <[email protected]> and
 *                           Philip Edelbrock <[email protected]>
 * Copyright (C) 2003 Greg Kroah-Hartman <[email protected]>
 * Copyright (C) 2003 IBM Corp.
 * Copyright (C) 2004 Jean Delvare <[email protected]>
 *
 * 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/init.h>
#include <linux/module.h>
#include <linux/slab.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;
    int err;

    if (!(data = kzalloc(sizeof(struct eeprom_data), GFP_KERNEL))) {
        err = -ENOMEM;
        goto exit;
    }

    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 */
    err = sysfs_create_bin_file(&client->dev.kobj, &eeprom_attr);
    if (err)
        goto exit_kfree;

    return 0;

exit_kfree:
    kfree(data);
exit:
    return err;
}

static int eeprom_remove(struct i2c_client *client)
{
    sysfs_remove_bin_file(&client->dev.kobj, &eeprom_attr);
    kfree(i2c_get_clientdata(client));

    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 <[email protected]> and "
        "Philip Edelbrock <[email protected]> and "
        "Greg Kroah-Hartman <[email protected]>");
MODULE_DESCRIPTION("I2C EEPROM driver");
MODULE_LICENSE("GPL");