/*
   * 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/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
  ", 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
  ");
  			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 <frodol@dds.nl> and "
  		"Philip Edelbrock <phil@netroedge.com> and "
  		"Greg Kroah-Hartman <greg@kroah.com>");
  MODULE_DESCRIPTION("I2C EEPROM driver");
  MODULE_LICENSE("GPL");