1/*
2    i2c-stub.c - Part of lm_sensors, Linux kernel modules for hardware
3              monitoring
4
5    Copyright (c) 2004 Mark M. Hoffman <mhoffman@lightlink.com>
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/errno.h>
28#include <linux/i2c.h>
29
30static unsigned short chip_addr;
31module_param(chip_addr, ushort, S_IRUGO);
32MODULE_PARM_DESC(chip_addr, "Chip address (between 0x03 and 0x77)\n");
33
34static u8  stub_pointer;
35static u8  stub_bytes[256];
36static u16 stub_words[256];
37
38/* Return -1 on error. */
39static s32 stub_xfer(struct i2c_adapter * adap, u16 addr, unsigned short flags,
40	char read_write, u8 command, int size, union i2c_smbus_data * data)
41{
42	s32 ret;
43
44	if (addr != chip_addr)
45		return -ENODEV;
46
47	switch (size) {
48
49	case I2C_SMBUS_QUICK:
50		dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
51		ret = 0;
52		break;
53
54	case I2C_SMBUS_BYTE:
55		if (read_write == I2C_SMBUS_WRITE) {
56			stub_pointer = command;
57			dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
58					"wrote 0x%02x.\n",
59					addr, command);
60		} else {
61			data->byte = stub_bytes[stub_pointer++];
62			dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
63					"read  0x%02x.\n",
64					addr, data->byte);
65		}
66
67		ret = 0;
68		break;
69
70	case I2C_SMBUS_BYTE_DATA:
71		if (read_write == I2C_SMBUS_WRITE) {
72			stub_bytes[command] = data->byte;
73			dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
74					"wrote 0x%02x at 0x%02x.\n",
75					addr, data->byte, command);
76		} else {
77			data->byte = stub_bytes[command];
78			dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
79					"read  0x%02x at 0x%02x.\n",
80					addr, data->byte, command);
81		}
82		stub_pointer = command + 1;
83
84		ret = 0;
85		break;
86
87	case I2C_SMBUS_WORD_DATA:
88		if (read_write == I2C_SMBUS_WRITE) {
89			stub_words[command] = data->word;
90			dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
91					"wrote 0x%04x at 0x%02x.\n",
92					addr, data->word, command);
93		} else {
94			data->word = stub_words[command];
95			dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
96					"read  0x%04x at 0x%02x.\n",
97					addr, data->word, command);
98		}
99
100		ret = 0;
101		break;
102
103	default:
104		dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
105		ret = -1;
106		break;
107	} /* switch (size) */
108
109	return ret;
110}
111
112static u32 stub_func(struct i2c_adapter *adapter)
113{
114	return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
115		I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA;
116}
117
118static const struct i2c_algorithm smbus_algorithm = {
119	.functionality	= stub_func,
120	.smbus_xfer	= stub_xfer,
121};
122
123static struct i2c_adapter stub_adapter = {
124	.owner		= THIS_MODULE,
125	.class		= I2C_CLASS_HWMON,
126	.algo		= &smbus_algorithm,
127	.name		= "SMBus stub driver",
128};
129
130static int __init i2c_stub_init(void)
131{
132	if (!chip_addr) {
133		printk(KERN_ERR "i2c-stub: Please specify a chip address\n");
134		return -ENODEV;
135	}
136	if (chip_addr < 0x03 || chip_addr > 0x77) {
137		printk(KERN_ERR "i2c-stub: Invalid chip address 0x%02x\n",
138		       chip_addr);
139		return -EINVAL;
140	}
141
142	printk(KERN_INFO "i2c-stub: Virtual chip at 0x%02x\n", chip_addr);
143	return i2c_add_adapter(&stub_adapter);
144}
145
146static void __exit i2c_stub_exit(void)
147{
148	i2c_del_adapter(&stub_adapter);
149}
150
151MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
152MODULE_DESCRIPTION("I2C stub driver");
153MODULE_LICENSE("GPL");
154
155module_init(i2c_stub_init);
156module_exit(i2c_stub_exit);
157