Help Regarding I2C Driver...

Uma Kanta Patro
2009-03-23T04:24:50Z

Hello,
This is Uma Kanta, seeking some help regarding the I2C
driver development on ARM Linux 2.6.19 platform.
I referred the second part of i2C driver articles in Linux Journal by Greg
Kroah. As well as the book Essential Linux Device Drivers.
I have to make I2C driver for a RTC (DS1340) and a camera module (Omnivision
OVM7670).
I could be able to make a chip driver. Unfortunately I was unable to insert
the core driver “i2c_core” internally. So I inserted the i2c_core.ko and my
own driver i2c_test.ko.
Now both drivers are getting inserted fine but the problem exists is:
In my init I am adding my i2c driver structure by using “i2c_add_driver()”,
and my i2c driver structure named “i2c_test_driver”, whose declaration is as
follows:

struct i2c_driver i2c_test_driver = {
.driver = {
.name   = "i2c_test",
},
.id = I2C_DRIVERID_OVCAMCHIP,            /* OmniVision CMOS
image sens.            *//* defined in include/linux/i2c-id.h */
.attach_adapter               = i2c_test_attach_adapter,
.detach_client   = i2c_test_detach_client,
};
static int __init i2c_test_init(void) {

char ret;
printk(KERN_INFO "In i2c_test_init\n");
ret = i2c_add_driver(&i2c_test_driver);
printk(KERN_INFO "i2c_test_init ret: %d\n",ret);
return ret;
}
Now “i2c_add_driver()” calls to “i2c_register_driver()”, residing in
KERN_SRC/drivers/i2c/i2c_core.c,
Inside i2c_register_driver()”, “driver_register()” is done, but the code
given below is bit complex:

/* now look for instances of driver on our adapters */
if (driver->attach_adapter) {
list_for_each(item,&adapters) {
adapter = list_entry(item,
struct i2c_adapter, list);

driver->attach_adapter(adapter);
printk("In
list_for_each\n");
}
}

So here “list_for_each(item,&adapters)” returns FALSE for me. So my attach
adapter function, “i2c_test_attach_adapter()” is not getting called.
So I searched where the entry “adapters” is getting a tail added in the
function “i2c_add_adapter()” So the function “i2c_add_adapter ()” will be
called by any client driver(as mentioned in comment…).
I tried by all “*.ko” files in KERN_SRC/drivers/i2c/algos/ but no effect.
So now to get the full functional I2C chip driver do I need to write a
client driver for it?

Can you please explain what are the minimum needs for the chip driver to be
functional?
And how can I get my driver working?
Thanks for sparing time for me.
Waiting for your reply…

With Regards,
Uma Kanta Patro