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Old 02-24-2010, 06:41 AM   #1
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Registered: Feb 2010
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I2C-GPIO-Bit bang

Hi Everybody,

I have a question, on using the available i2c-gpio driver in linux kernel.
If I do a lsmod I can see the loaded driver, but can't see any relevant devie nod in /dev directory.It has been registered as platform driver.

How can I access this driver from user space.?
If I need to create a /dev node, then how can I get the major no.?

I am attaching the driver for your review.

Any help will be appreciated.

Many thanks, betz


struct i2c_s3c2410_bit {
struct i2c_adapter adap;
struct i2c_algo_bit_data algo;

static void i2c_s3c2410_bit_setsda(void *data, int state)
if (state)
s3c2410_gpio_cfgpin(S3C2410_GPD8, S3C2410_GPIO_INPUT);
s3c2410_gpio_setpin(S3C2410_GPD8, 0);
s3c2410_gpio_cfgpin(S3C2410_GPD8, S3C2410_GPIO_OUTPUT);

static void i2c_s3c2410_bit_setscl(void *data, int state)
if (state)
s3c2410_gpio_cfgpin(S3C2410_GPD9, S3C2410_GPIO_INPUT);
s3c2410_gpio_setpin(S3C2410_GPD9, 0);
s3c2410_gpio_cfgpin(S3C2410_GPD9, S3C2410_GPIO_OUTPUT);

static int i2c_s3c2410_bit_getsda(void *data)
return !!s3c2410_gpio_getpin(S3C2410_GPD8);

static int i2c_s3c2410_bit_getscl(void *data)
return !!s3c2410_gpio_getpin(S3C2410_GPD9);

static struct i2c_algo_bit_data i2c_s3c2410_bit_algo = {
.setsda = i2c_s3c2410_bit_setsda,
.setscl = i2c_s3c2410_bit_setscl,
.getsda = i2c_s3c2410_bit_getsda,
.getscl = i2c_s3c2410_bit_getscl,
.udelay = 100,
.timeout = HZ,

static int i2c_s3c2410_bit_probe(struct platform_device *dev)
// printk("%s\n", __FUNCTION__);
struct i2c_s3c2410_bit *i2c;
int ret;

printk("%s\n", __func__);

i2c = kzalloc(sizeof(struct i2c_s3c2410_bit), GFP_KERNEL);
if (!i2c) {
ret = -ENOMEM;
goto err_out;

s3c2410_gpio_cfgpin(S3C2410_GPD9, S3C2410_GPIO_INPUT);
s3c2410_gpio_cfgpin(S3C2410_GPD8, S3C2410_GPIO_INPUT);

i2c->adap.owner = THIS_MODULE;
strlcpy(i2c->, "S3C2410 bit-bang I2C adapter", sizeof(i2c->;
i2c->adap.algo_data = &i2c->algo;
i2c-> = &dev->dev;
i2c->algo = i2c_s3c2410_bit_algo;
i2c-> = i2c;

ret = i2c_bit_add_bus(&i2c->adap);
if (ret >= 0) {
platform_set_drvdata(dev, i2c);
return 0;

return ret;

static int i2c_s3c2410_bit_remove(struct platform_device *dev)
struct i2c_s3c2410_bit *i2c = platform_get_drvdata(dev);

platform_set_drvdata(dev, NULL);

return 0;

static struct platform_driver i2c_s3c2410_bit_driver = {
.probe = i2c_s3c2410_bit_probe,
.remove = i2c_s3c2410_bit_remove,
.driver = {
.name = "s3c2410-i2c-bit",
.owner = THIS_MODULE,

static int __init i2c_s3c2410_bit_init(void)

return platform_driver_register(&i2c_s3c2410_bit_driver);

static void __exit i2c_s3c2410_bit_exit(void)



MODULE_DESCRIPTION("S3C2410 bit-bang I2C bus driver");



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