I2C device driver to simutaneously support 2 devices

I am trying to modify the I2C linux device driver code by Gregg Koah-Hartman ( http://www.linuxjournal.com/article/7252 )to enable the driver to simultaneously support 2 devices. The second device will be on a different I2C address from the first device.

Can anyone kindly advise on where I should start the modification? My initial suspicion is to append another i2c_add_driver function at the function static int __init tiny_init(void) [Refer to the codes below]
Would this work? I currently have trouble registering the second device as the driver wouldn't load. Kindly advise.

FTP link for the driver file frm Gregg Koah-Hartman's I2C driver code in Linux Journal is as follows: ftp://ftp.ssc.com/pub/lj/listings/issue118/7252.tgz

The code is as follows:
* Tiny I2C Chip Driver
* Copyright (C) 2003 Greg Kroah-Hartman (greg@kroah.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, version 2 of the License.
* This driver shows how to create a minimal I2C bus and algorithm driver.
* Compile this driver with:

echo "obj-m := tiny_i2c_chip.o" > Makefile
make -C SUBDIRS=$PWD modules

#define DEBUG 1


/* Addresses to scan */
static unsigned short normal_i2c[] = { I2C_CLIENT_END };
static unsigned short normal_i2c_range[] = { 0x00, 0xff, I2C_CLIENT_END };
static unsigned int normal_isa[] = { I2C_CLIENT_ISA_END };
static unsigned int normal_isa_range[] = { I2C_CLIENT_ISA_END };

/* Insmod parameters */

/* Each client has this additional data */
struct chip_data {
struct semaphore update_lock;
char valid; /* !=0 if following fields are valid */
unsigned long last_updated; /* In jiffies */
u16 temp_input; /* Register values */
u16 temp_max;
u16 temp_hyst;

#define REG_TEMP_HYST 0x01
#define REG_TEMP_OS 0x02

static int chip_attach_adapter(struct i2c_adapter *adapter);
static int chip_detect(struct i2c_adapter *adapter, int address, int kind);
static int chip_detach_client(struct i2c_client *client);

/* This is the driver that will be inserted */
static struct i2c_driver chip_driver = {
.owner = THIS_MODULE,
.name = "tiny_chip",
.flags = I2C_DF_NOTIFY,
.attach_adapter = chip_attach_adapter,
.detach_client = chip_detach_client,

static void chip_update_client(struct i2c_client *client)
struct chip_data *data = i2c_get_clientdata(client);

dev_dbg(&client->dev, "%s\n", __FUNCTION__);
data->last_updated = jiffies;
data->valid = 1;

#define show(value) \
static ssize_t show_##value(struct device *dev, char *buf) \
{ \
struct i2c_client *client = to_i2c_client(dev); \
struct chip_data *data = i2c_get_clientdata(client); \
chip_update_client(client); \
return sprintf(buf, "%d\n", data->value); \

#define set(value, reg) \
static ssize_t set_##value(struct device *dev, const char *buf, size_t count) \
{ \
struct i2c_client *client = to_i2c_client(dev); \
struct chip_data *data = i2c_get_clientdata(client); \
int temp = simple_strtoul(buf, NULL, 10); \
down(&data->update_lock); \
data->value = temp; \
up(&data->update_lock); \
return count; \
set(temp_max, REG_TEMP_OS);
set(temp_hyst, REG_TEMP_HYST);

static DEVICE_ATTR(temp_max, S_IWUSR | S_IRUGO, show_temp_max, set_temp_max);
static DEVICE_ATTR(temp_min, S_IWUSR | S_IRUGO, show_temp_hyst, set_temp_hyst);
static DEVICE_ATTR(temp_input, S_IRUGO, show_temp_input, NULL);

static int chip_attach_adapter(struct i2c_adapter *adapter)
return i2c_detect(adapter, &addr_data, chip_detect);

/* This function is called by i2c_detect */
static int chip_detect(struct i2c_adapter *adapter, int address, int kind)
struct i2c_client *new_client = NULL;
struct chip_data *data = NULL;
int err = 0;

if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
goto error;

new_client = kmalloc(sizeof(*new_client), GFP_KERNEL);
if (!new_client) {
err = -ENOMEM;
goto error;
data = kmalloc(sizeof(*data), GFP_KERNEL);
if (!data) {
err = -ENOMEM;
goto error;

memset(new_client, 0x00, sizeof(*new_client));
memset(data, 0x00, sizeof(*data));

i2c_set_clientdata(new_client, data);
new_client->addr = address;
new_client->adapter = adapter;
new_client->driver = &chip_driver;
new_client->flags = 0;

/* Fill in the remaining client fields */
strncpy(new_client->name, "tiny_chip", I2C_NAME_SIZE);
data->valid = 0;

/* Tell the I2C layer a new client has arrived */
err = i2c_attach_client(new_client);
if (err)
goto error;

/* Register sysfs files */
device_create_file(&new_client->dev, &dev_attr_temp_max);
device_create_file(&new_client->dev, &dev_attr_temp_min);
device_create_file(&new_client->dev, &dev_attr_temp_input);

return 0;

return err;

static int chip_detach_client(struct i2c_client *client)
struct chip_data *data = i2c_get_clientdata(client);
int err;

err = i2c_detach_client(client);
if (err) {
dev_err(&client->dev, "Client deregistration failed, client not detached.\n");
return err;

return 0;

static int __init tiny_init(void)
return i2c_add_driver(&chip_driver);

static void __exit tiny_exit(void)

MODULE_AUTHOR("Greg Kroah-Hartman ");
MODULE_DESCRIPTION("Tiny i2c chip");


Thanks in advance.

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