Linux 2.6.31-rc6
[linux-2.6] / drivers / i2c / busses / i2c-stub.c
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. */
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
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
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
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