/*
    i2c-stub.c - Part of lm_sensors, Linux kernel modules for hardware
              monitoring

    Copyright (c) 2004 Mark M. Hoffman <mhoffman@lightlink.com>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#define DEBUG 1

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/i2c.h>

static unsigned short chip_addr;
module_param(chip_addr, ushort, S_IRUGO);
MODULE_PARM_DESC(chip_addr, "Chip address (between 0x03 and 0x77)\n");

static u8  stub_pointer;
static u8  stub_bytes[256];
static u16 stub_words[256];

/* Return -1 on error. */
static s32 stub_xfer(struct i2c_adapter * adap, u16 addr, unsigned short flags,
	char read_write, u8 command, int size, union i2c_smbus_data * data)
{
	s32 ret;

	if (addr != chip_addr)
		return -ENODEV;

	switch (size) {

	case I2C_SMBUS_QUICK:
		dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
		ret = 0;
		break;

	case I2C_SMBUS_BYTE:
		if (read_write == I2C_SMBUS_WRITE) {
			stub_pointer = command;
			dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
					"wrote 0x%02x.\n",
					addr, command);
		} else {
			data->byte = stub_bytes[stub_pointer++];
			dev_dbg(&adap->dev, "smbus byte - addr 0x%02x, "
					"read  0x%02x.\n",
					addr, data->byte);
		}

		ret = 0;
		break;

	case I2C_SMBUS_BYTE_DATA:
		if (read_write == I2C_SMBUS_WRITE) {
			stub_bytes[command] = data->byte;
			dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
					"wrote 0x%02x at 0x%02x.\n",
					addr, data->byte, command);
		} else {
			data->byte = stub_bytes[command];
			dev_dbg(&adap->dev, "smbus byte data - addr 0x%02x, "
					"read  0x%02x at 0x%02x.\n",
					addr, data->byte, command);
		}
		stub_pointer = command + 1;

		ret = 0;
		break;

	case I2C_SMBUS_WORD_DATA:
		if (read_write == I2C_SMBUS_WRITE) {
			stub_words[command] = data->word;
			dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
					"wrote 0x%04x at 0x%02x.\n",
					addr, data->word, command);
		} else {
			data->word = stub_words[command];
			dev_dbg(&adap->dev, "smbus word data - addr 0x%02x, "
					"read  0x%04x at 0x%02x.\n",
					addr, data->word, command);
		}

		ret = 0;
		break;

	default:
		dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
		ret = -1;
		break;
	} /* switch (size) */

	return ret;
}

static u32 stub_func(struct i2c_adapter *adapter)
{
	return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
		I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA;
}

static const struct i2c_algorithm smbus_algorithm = {
	.functionality	= stub_func,
	.smbus_xfer	= stub_xfer,
};

static struct i2c_adapter stub_adapter = {
	.owner		= THIS_MODULE,
	.class		= I2C_CLASS_HWMON,
	.algo		= &smbus_algorithm,
	.name		= "SMBus stub driver",
};

static int __init i2c_stub_init(void)
{
	if (!chip_addr) {
		printk(KERN_ERR "i2c-stub: Please specify a chip address\n");
		return -ENODEV;
	}
	if (chip_addr < 0x03 || chip_addr > 0x77) {
		printk(KERN_ERR "i2c-stub: Invalid chip address 0x%02x\n",
		       chip_addr);
		return -EINVAL;
	}

	printk(KERN_INFO "i2c-stub: Virtual chip at 0x%02x\n", chip_addr);
	return i2c_add_adapter(&stub_adapter);
}

static void __exit i2c_stub_exit(void)
{
	i2c_del_adapter(&stub_adapter);
}

MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
MODULE_DESCRIPTION("I2C stub driver");
MODULE_LICENSE("GPL");

module_init(i2c_stub_init);
module_exit(i2c_stub_exit);