xref: /openbmc/linux/drivers/misc/eeprom/eeprom.c (revision 0edbfea5)
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/jiffies.h>
23 #include <linux/i2c.h>
24 #include <linux/mutex.h>
25 
26 /* Addresses to scan */
27 static const unsigned short normal_i2c[] = { 0x50, 0x51, 0x52, 0x53, 0x54,
28 					0x55, 0x56, 0x57, I2C_CLIENT_END };
29 
30 
31 /* Size of EEPROM in bytes */
32 #define EEPROM_SIZE		256
33 
34 /* possible types of eeprom devices */
35 enum eeprom_nature {
36 	UNKNOWN,
37 	VAIO,
38 };
39 
40 /* Each client has this additional data */
41 struct eeprom_data {
42 	struct mutex update_lock;
43 	u8 valid;			/* bitfield, bit!=0 if slice is valid */
44 	unsigned long last_updated[8];	/* In jiffies, 8 slices */
45 	u8 data[EEPROM_SIZE];		/* Register values */
46 	enum eeprom_nature nature;
47 };
48 
49 
50 static void eeprom_update_client(struct i2c_client *client, u8 slice)
51 {
52 	struct eeprom_data *data = i2c_get_clientdata(client);
53 	int i;
54 
55 	mutex_lock(&data->update_lock);
56 
57 	if (!(data->valid & (1 << slice)) ||
58 	    time_after(jiffies, data->last_updated[slice] + 300 * HZ)) {
59 		dev_dbg(&client->dev, "Starting eeprom update, slice %u\n", slice);
60 
61 		if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
62 			for (i = slice << 5; i < (slice + 1) << 5; i += 32)
63 				if (i2c_smbus_read_i2c_block_data(client, i,
64 							32, data->data + i)
65 							!= 32)
66 					goto exit;
67 		} else {
68 			for (i = slice << 5; i < (slice + 1) << 5; i += 2) {
69 				int word = i2c_smbus_read_word_data(client, i);
70 				if (word < 0)
71 					goto exit;
72 				data->data[i] = word & 0xff;
73 				data->data[i + 1] = word >> 8;
74 			}
75 		}
76 		data->last_updated[slice] = jiffies;
77 		data->valid |= (1 << slice);
78 	}
79 exit:
80 	mutex_unlock(&data->update_lock);
81 }
82 
83 static ssize_t eeprom_read(struct file *filp, struct kobject *kobj,
84 			   struct bin_attribute *bin_attr,
85 			   char *buf, loff_t off, size_t count)
86 {
87 	struct i2c_client *client = to_i2c_client(kobj_to_dev(kobj));
88 	struct eeprom_data *data = i2c_get_clientdata(client);
89 	u8 slice;
90 
91 	/* Only refresh slices which contain requested bytes */
92 	for (slice = off >> 5; slice <= (off + count - 1) >> 5; slice++)
93 		eeprom_update_client(client, slice);
94 
95 	/* Hide Vaio private settings to regular users:
96 	   - BIOS passwords: bytes 0x00 to 0x0f
97 	   - UUID: bytes 0x10 to 0x1f
98 	   - Serial number: 0xc0 to 0xdf */
99 	if (data->nature == VAIO && !capable(CAP_SYS_ADMIN)) {
100 		int i;
101 
102 		for (i = 0; i < count; i++) {
103 			if ((off + i <= 0x1f) ||
104 			    (off + i >= 0xc0 && off + i <= 0xdf))
105 				buf[i] = 0;
106 			else
107 				buf[i] = data->data[off + i];
108 		}
109 	} else {
110 		memcpy(buf, &data->data[off], count);
111 	}
112 
113 	return count;
114 }
115 
116 static struct bin_attribute eeprom_attr = {
117 	.attr = {
118 		.name = "eeprom",
119 		.mode = S_IRUGO,
120 	},
121 	.size = EEPROM_SIZE,
122 	.read = eeprom_read,
123 };
124 
125 /* Return 0 if detection is successful, -ENODEV otherwise */
126 static int eeprom_detect(struct i2c_client *client, struct i2c_board_info *info)
127 {
128 	struct i2c_adapter *adapter = client->adapter;
129 
130 	/* EDID EEPROMs are often 24C00 EEPROMs, which answer to all
131 	   addresses 0x50-0x57, but we only care about 0x50. So decline
132 	   attaching to addresses >= 0x51 on DDC buses */
133 	if (!(adapter->class & I2C_CLASS_SPD) && client->addr >= 0x51)
134 		return -ENODEV;
135 
136 	/* There are four ways we can read the EEPROM data:
137 	   (1) I2C block reads (faster, but unsupported by most adapters)
138 	   (2) Word reads (128% overhead)
139 	   (3) Consecutive byte reads (88% overhead, unsafe)
140 	   (4) Regular byte data reads (265% overhead)
141 	   The third and fourth methods are not implemented by this driver
142 	   because all known adapters support one of the first two. */
143 	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_WORD_DATA)
144 	 && !i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK))
145 		return -ENODEV;
146 
147 	strlcpy(info->type, "eeprom", I2C_NAME_SIZE);
148 
149 	return 0;
150 }
151 
152 static int eeprom_probe(struct i2c_client *client,
153 			const struct i2c_device_id *id)
154 {
155 	struct i2c_adapter *adapter = client->adapter;
156 	struct eeprom_data *data;
157 
158 	data = devm_kzalloc(&client->dev, sizeof(struct eeprom_data),
159 			    GFP_KERNEL);
160 	if (!data)
161 		return -ENOMEM;
162 
163 	memset(data->data, 0xff, EEPROM_SIZE);
164 	i2c_set_clientdata(client, data);
165 	mutex_init(&data->update_lock);
166 	data->nature = UNKNOWN;
167 
168 	/* Detect the Vaio nature of EEPROMs.
169 	   We use the "PCG-" or "VGN-" prefix as the signature. */
170 	if (client->addr == 0x57
171 	 && i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
172 		char name[4];
173 
174 		name[0] = i2c_smbus_read_byte_data(client, 0x80);
175 		name[1] = i2c_smbus_read_byte_data(client, 0x81);
176 		name[2] = i2c_smbus_read_byte_data(client, 0x82);
177 		name[3] = i2c_smbus_read_byte_data(client, 0x83);
178 
179 		if (!memcmp(name, "PCG-", 4) || !memcmp(name, "VGN-", 4)) {
180 			dev_info(&client->dev, "Vaio EEPROM detected, "
181 				 "enabling privacy protection\n");
182 			data->nature = VAIO;
183 		}
184 	}
185 
186 	/* create the sysfs eeprom file */
187 	return sysfs_create_bin_file(&client->dev.kobj, &eeprom_attr);
188 }
189 
190 static int eeprom_remove(struct i2c_client *client)
191 {
192 	sysfs_remove_bin_file(&client->dev.kobj, &eeprom_attr);
193 
194 	return 0;
195 }
196 
197 static const struct i2c_device_id eeprom_id[] = {
198 	{ "eeprom", 0 },
199 	{ }
200 };
201 
202 static struct i2c_driver eeprom_driver = {
203 	.driver = {
204 		.name	= "eeprom",
205 	},
206 	.probe		= eeprom_probe,
207 	.remove		= eeprom_remove,
208 	.id_table	= eeprom_id,
209 
210 	.class		= I2C_CLASS_DDC | I2C_CLASS_SPD,
211 	.detect		= eeprom_detect,
212 	.address_list	= normal_i2c,
213 };
214 
215 module_i2c_driver(eeprom_driver);
216 
217 MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl> and "
218 		"Philip Edelbrock <phil@netroedge.com> and "
219 		"Greg Kroah-Hartman <greg@kroah.com>");
220 MODULE_DESCRIPTION("I2C EEPROM driver");
221 MODULE_LICENSE("GPL");
222