Getting data from a rtc device through I2C

Actually, when parsing the device tree, the i2c-gpio driver could not retrieve the 'gpios' field use to describe the SDA and SCL pins. So I decided to come back to a module which create an i2c bus and then, populate this bus.

# include <linux/module.h>
# include <linux/init.h>
# include <linux/i2c-gpio.h>
# include <linux/i2c.h>
# include <linux/platform_device.h>
# include <linux/kernel.h>
# define GPIO_RTC_SDA		100
# define GPIO_RTC_SCL		99
MODULE_DESCRIPTION("i2c via gpio module");
MODULE_LICENSE("GPL");
static struct i2c_gpio_platform_data rtc_device_data = {
	.sda_pin = GPIO_RTC_SDA,
	.scl_pin = GPIO_RTC_SCL,
	.udelay  = 2.5,				//f=400kHz
	.scl_is_open_drain = 1,
	.sda_is_open_drain = 1
};
static struct platform_device i2c_gpio_bus_rtc = {
	.name 	= "i2c-gpio",
	.id		= 0,
	.dev	= {
		.platform_data = &rtc_device_data,
	}
};
static struct i2c_board_info i2c_gpio_bus_devices = {
	{
		I2C_BOARD_INFO("m41t83", 0x68),
		.platform_data = &rtc_device_data,
	},
};
static int __init i2c_gpio_bus_init(void)
{
	int ret;
	struct i2c_adapter *bus;
	struct i2c_client *rtc;
    ret = platform_device_register(&i2c_gpio_bus_rtc);
	if (ret)
		printk(KERN_ERR "i2c_bus_driver: Error when registering: %d\n", 
		ret);
	/* Populate bus */
	bus = i2c_get_adapter(0);
	rtc = i2c_new_device(bus, i2c_gpio_bus_devices);
	if (rtc == NULL)
		printk(KERN_ERR "i2c_bus_driver: no device added to %s bus\n",
		bus->name);
	
	return ret;
}
static void __exit i2c_gpio_bus_exit(void)
{
	platform_device_unregister(&i2c_gpio_bus_rtc);
}
module_init(i2c_gpio_bus_init);
module_exit(i2c_gpio_bus_exit);