1/*
  2 * Copyright (C) 1998, 1999  Frodo Looijaard <frodol@dds.nl> and
  3 *                           Philip Edelbrock <phil@netroedge.com>
  4 * Copyright (C) 2003 Greg Kroah-Hartman <greg@kroah.com>
  5 * Copyright (C) 2003 IBM Corp.
  6 * Copyright (C) 2004 Jean Delvare <jdelvare@suse.de>
  7 *
  8 * This program is free software; you can redistribute it and/or modify
  9 * it under the terms of the GNU General Public License as published by
 10 * the Free Software Foundation; either version 2 of the License, or
 11 * (at your option) any later version.
 12 *
 13 * This program is distributed in the hope that it will be useful,
 14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 16 * GNU General Public License for more details.
 17 */
 18
 19#include <linux/kernel.h>
 20#include <linux/module.h>
 21#include <linux/device.h>
 22#include <linux/capability.h>
 23#include <linux/jiffies.h>
 24#include <linux/i2c.h>
 25#include <linux/mutex.h>
 26
 27/* Addresses to scan */
 28static const unsigned short normal_i2c[] = { 0x50, 0x51, 0x52, 0x53, 0x54,
 29					0x55, 0x56, 0x57, I2C_CLIENT_END };
 30
 31
 32/* Size of EEPROM in bytes */
 33#define EEPROM_SIZE		256
 34
 35/* possible types of eeprom devices */
 36enum eeprom_nature {
 37	UNKNOWN,
 38	VAIO,
 39};
 40
 41/* Each client has this additional data */
 42struct eeprom_data {
 43	struct mutex update_lock;
 44	u8 valid;			/* bitfield, bit!=0 if slice is valid */
 45	unsigned long last_updated[8];	/* In jiffies, 8 slices */
 46	u8 data[EEPROM_SIZE];		/* Register values */
 47	enum eeprom_nature nature;
 48};
 49
 50
 51static void eeprom_update_client(struct i2c_client *client, u8 slice)
 52{
 53	struct eeprom_data *data = i2c_get_clientdata(client);
 54	int i;
 55
 56	mutex_lock(&data->update_lock);
 57
 58	if (!(data->valid & (1 << slice)) ||
 59	    time_after(jiffies, data->last_updated[slice] + 300 * HZ)) {
 60		dev_dbg(&client->dev, "Starting eeprom update, slice %u\n", slice);
 61
 62		if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
 63			for (i = slice << 5; i < (slice + 1) << 5; i += 32)
 64				if (i2c_smbus_read_i2c_block_data(client, i,
 65							32, data->data + i)
 66							!= 32)
 67					goto exit;
 68		} else {
 69			for (i = slice << 5; i < (slice + 1) << 5; i += 2) {
 70				int word = i2c_smbus_read_word_data(client, i);
 71				if (word < 0)
 72					goto exit;
 73				data->data[i] = word & 0xff;
 74				data->data[i + 1] = word >> 8;
 75			}
 76		}
 77		data->last_updated[slice] = jiffies;
 78		data->valid |= (1 << slice);
 79	}
 80exit:
 81	mutex_unlock(&data->update_lock);
 82}
 83
 84static ssize_t eeprom_read(struct file *filp, struct kobject *kobj,
 85			   struct bin_attribute *bin_attr,
 86			   char *buf, loff_t off, size_t count)
 87{
 88	struct i2c_client *client = to_i2c_client(kobj_to_dev(kobj));
 89	struct eeprom_data *data = i2c_get_clientdata(client);
 90	u8 slice;
 91
 92	/* Only refresh slices which contain requested bytes */
 93	for (slice = off >> 5; slice <= (off + count - 1) >> 5; slice++)
 94		eeprom_update_client(client, slice);
 95
 96	/* Hide Vaio private settings to regular users:
 97	   - BIOS passwords: bytes 0x00 to 0x0f
 98	   - UUID: bytes 0x10 to 0x1f
 99	   - Serial number: 0xc0 to 0xdf */
100	if (data->nature == VAIO && !capable(CAP_SYS_ADMIN)) {
101		int i;
102
103		for (i = 0; i < count; i++) {
104			if ((off + i <= 0x1f) ||
105			    (off + i >= 0xc0 && off + i <= 0xdf))
106				buf[i] = 0;
107			else
108				buf[i] = data->data[off + i];
109		}
110	} else {
111		memcpy(buf, &data->data[off], count);
112	}
113
114	return count;
115}
116
117static const struct bin_attribute eeprom_attr = {
118	.attr = {
119		.name = "eeprom",
120		.mode = S_IRUGO,
121	},
122	.size = EEPROM_SIZE,
123	.read = eeprom_read,
124};
125
126/* Return 0 if detection is successful, -ENODEV otherwise */
127static int eeprom_detect(struct i2c_client *client, struct i2c_board_info *info)
128{
129	struct i2c_adapter *adapter = client->adapter;
130
131	/* EDID EEPROMs are often 24C00 EEPROMs, which answer to all
132	   addresses 0x50-0x57, but we only care about 0x50. So decline
133	   attaching to addresses >= 0x51 on DDC buses */
134	if (!(adapter->class & I2C_CLASS_SPD) && client->addr >= 0x51)
135		return -ENODEV;
136
137	/* There are four ways we can read the EEPROM data:
138	   (1) I2C block reads (faster, but unsupported by most adapters)
139	   (2) Word reads (128% overhead)
140	   (3) Consecutive byte reads (88% overhead, unsafe)
141	   (4) Regular byte data reads (265% overhead)
142	   The third and fourth methods are not implemented by this driver
143	   because all known adapters support one of the first two. */
144	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_WORD_DATA)
145	 && !i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK))
146		return -ENODEV;
147
148	strlcpy(info->type, "eeprom", I2C_NAME_SIZE);
149
150	return 0;
151}
152
153static int eeprom_probe(struct i2c_client *client,
154			const struct i2c_device_id *id)
155{
156	struct i2c_adapter *adapter = client->adapter;
157	struct eeprom_data *data;
158
159	data = devm_kzalloc(&client->dev, sizeof(struct eeprom_data),
160			    GFP_KERNEL);
161	if (!data)
162		return -ENOMEM;
163
164	memset(data->data, 0xff, EEPROM_SIZE);
165	i2c_set_clientdata(client, data);
166	mutex_init(&data->update_lock);
167	data->nature = UNKNOWN;
168
169	/* Detect the Vaio nature of EEPROMs.
170	   We use the "PCG-" or "VGN-" prefix as the signature. */
171	if (client->addr == 0x57
172	 && i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
173		char name[4];
174
175		name[0] = i2c_smbus_read_byte_data(client, 0x80);
176		name[1] = i2c_smbus_read_byte_data(client, 0x81);
177		name[2] = i2c_smbus_read_byte_data(client, 0x82);
178		name[3] = i2c_smbus_read_byte_data(client, 0x83);
179
180		if (!memcmp(name, "PCG-", 4) || !memcmp(name, "VGN-", 4)) {
181			dev_info(&client->dev, "Vaio EEPROM detected, "
182				 "enabling privacy protection\n");
183			data->nature = VAIO;
184		}
185	}
186
187	/* create the sysfs eeprom file */
188	return sysfs_create_bin_file(&client->dev.kobj, &eeprom_attr);
189}
190
191static int eeprom_remove(struct i2c_client *client)
192{
193	sysfs_remove_bin_file(&client->dev.kobj, &eeprom_attr);
194
195	return 0;
196}
197
198static const struct i2c_device_id eeprom_id[] = {
199	{ "eeprom", 0 },
200	{ }
201};
202
203static struct i2c_driver eeprom_driver = {
204	.driver = {
205		.name	= "eeprom",
206	},
207	.probe		= eeprom_probe,
208	.remove		= eeprom_remove,
209	.id_table	= eeprom_id,
210
211	.class		= I2C_CLASS_DDC | I2C_CLASS_SPD,
212	.detect		= eeprom_detect,
213	.address_list	= normal_i2c,
214};
215
216module_i2c_driver(eeprom_driver);
217
218MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl> and "
219		"Philip Edelbrock <phil@netroedge.com> and "
220		"Greg Kroah-Hartman <greg@kroah.com>");
221MODULE_DESCRIPTION("I2C EEPROM driver");
222MODULE_LICENSE("GPL");