1 /*
2 i2c-stub.c - I2C/SMBus chip emulator
3
4 Copyright (c) 2004 Mark M. Hoffman <mhoffman@lightlink.com>
5 Copyright (C) 2007 Jean Delvare <khali@linux-fr.org>
6
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
11
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
20 */
21
22 #define DEBUG 1
23
24 #include <linux/init.h>
25 #include <linux/module.h>
26 #include <linux/kernel.h>
27 #include <linux/slab.h>
28 #include <linux/errno.h>
29 #include <linux/i2c.h>
30
31 #define MAX_CHIPS 10
32
33 static unsigned short chip_addr[MAX_CHIPS];
34 module_param_array(chip_addr, ushort, NULL, S_IRUGO);
35 MODULE_PARM_DESC(chip_addr,
36 "Chip addresses (up to 10, between 0x03 and 0x77)");
37
38 struct stub_chip {
39 u8 pointer;
40 u16 words[256]; /* Byte operations use the LSB as per SMBus
41 specification */
42 };
43
44 static struct stub_chip *stub_chips;
45
46 /* Return negative errno on error. */
stub_xfer(struct i2c_adapter * adap,u16 addr,unsigned short flags,char read_write,u8 command,int size,union i2c_smbus_data * data)47 static s32 stub_xfer(struct i2c_adapter * adap, u16 addr, unsigned short flags,
48 char read_write, u8 command, int size, union i2c_smbus_data * data)
49 {
50 s32 ret;
51 int i;
52 struct stub_chip *chip = NULL;
53
54 /* Search for the right chip */
55 for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
56 if (addr == chip_addr[i]) {
57 chip = stub_chips + i;
58 break;
59 }
60 }
61 if (!chip)
62 return -ENODEV;
63
64 switch (size) {
65
66 case I2C_SMBUS_QUICK:
67 dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
68 ret = 0;
69 break;
70
71 case I2C_SMBUS_BYTE:
72 if (read_write == I2C_SMBUS_WRITE) {
73 chip->pointer = command;
74 dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
75 "wrote 0x%02x.\n",
76 addr, command);
77 } else {
78 data->byte = chip->words[chip->pointer++] & 0xff;
79 dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
80 "read 0x%02x.\n",
81 addr, data->byte);
82 }
83
84 ret = 0;
85 break;
86
87 case I2C_SMBUS_BYTE_DATA:
88 if (read_write == I2C_SMBUS_WRITE) {
89 chip->words[command] &= 0xff00;
90 chip->words[command] |= data->byte;
91 dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
92 "wrote 0x%02x at 0x%02x.\n",
93 addr, data->byte, command);
94 } else {
95 data->byte = chip->words[command] & 0xff;
96 dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
97 "read 0x%02x at 0x%02x.\n",
98 addr, data->byte, command);
99 }
100 chip->pointer = command + 1;
101
102 ret = 0;
103 break;
104
105 case I2C_SMBUS_WORD_DATA:
106 if (read_write == I2C_SMBUS_WRITE) {
107 chip->words[command] = data->word;
108 dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
109 "wrote 0x%04x at 0x%02x.\n",
110 addr, data->word, command);
111 } else {
112 data->word = chip->words[command];
113 dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
114 "read 0x%04x at 0x%02x.\n",
115 addr, data->word, command);
116 }
117
118 ret = 0;
119 break;
120
121 default:
122 dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
123 ret = -EOPNOTSUPP;
124 break;
125 } /* switch (size) */
126
127 return ret;
128 }
129
stub_func(struct i2c_adapter * adapter)130 static u32 stub_func(struct i2c_adapter *adapter)
131 {
132 return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
133 I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA;
134 }
135
136 static const struct i2c_algorithm smbus_algorithm = {
137 .functionality = stub_func,
138 .smbus_xfer = stub_xfer,
139 };
140
141 static struct i2c_adapter stub_adapter = {
142 .owner = THIS_MODULE,
143 .class = I2C_CLASS_HWMON | I2C_CLASS_SPD,
144 .algo = &smbus_algorithm,
145 .name = "SMBus stub driver",
146 };
147
i2c_stub_init(void)148 static int __init i2c_stub_init(void)
149 {
150 int i, ret;
151
152 if (!chip_addr[0]) {
153 printk(KERN_ERR "i2c-stub: Please specify a chip address\n");
154 return -ENODEV;
155 }
156
157 for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
158 if (chip_addr[i] < 0x03 || chip_addr[i] > 0x77) {
159 printk(KERN_ERR "i2c-stub: Invalid chip address "
160 "0x%02x\n", chip_addr[i]);
161 return -EINVAL;
162 }
163
164 printk(KERN_INFO "i2c-stub: Virtual chip at 0x%02x\n",
165 chip_addr[i]);
166 }
167
168 /* Allocate memory for all chips at once */
169 stub_chips = kzalloc(i * sizeof(struct stub_chip), GFP_KERNEL);
170 if (!stub_chips) {
171 printk(KERN_ERR "i2c-stub: Out of memory\n");
172 return -ENOMEM;
173 }
174
175 ret = i2c_add_adapter(&stub_adapter);
176 if (ret)
177 kfree(stub_chips);
178 return ret;
179 }
180
i2c_stub_exit(void)181 static void __exit i2c_stub_exit(void)
182 {
183 i2c_del_adapter(&stub_adapter);
184 kfree(stub_chips);
185 }
186
187 MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
188 MODULE_DESCRIPTION("I2C stub driver");
189 MODULE_LICENSE("GPL");
190
191 module_init(i2c_stub_init);
192 module_exit(i2c_stub_exit);
193
194