xref: /openbmc/linux/drivers/misc/eeprom/eeprom.c (revision 791d3ef2)
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 */
28 static 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 */
36 enum eeprom_nature {
37 	UNKNOWN,
38 	VAIO,
39 };
40 
41 /* Each client has this additional data */
42 struct 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 
51 static 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 	}
80 exit:
81 	mutex_unlock(&data->update_lock);
82 }
83 
84 static 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 
117 static 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 */
127 static 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 
153 static 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 
191 static int eeprom_remove(struct i2c_client *client)
192 {
193 	sysfs_remove_bin_file(&client->dev.kobj, &eeprom_attr);
194 
195 	return 0;
196 }
197 
198 static const struct i2c_device_id eeprom_id[] = {
199 	{ "eeprom", 0 },
200 	{ }
201 };
202 
203 static 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 
216 module_i2c_driver(eeprom_driver);
217 
218 MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl> and "
219 		"Philip Edelbrock <phil@netroedge.com> and "
220 		"Greg Kroah-Hartman <greg@kroah.com>");
221 MODULE_DESCRIPTION("I2C EEPROM driver");
222 MODULE_LICENSE("GPL");
223