Re: Help Regarding I2C Driver...

Daniel Mack
2009-03-23T08:40:34Z

On Mon, Mar 23, 2009 at 09:54:50AM +0530, Uma Kanta Patro wrote:
>                 This is Uma Kanta, seeking some help regarding the I2C
> driver development on ARM Linux 2.6.19 platform.

This version is ancient, you should consider updating to something more
recent.

> 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,
> };

attach_adapter and friends are legacy callbacks, you should not use them
in new drivers. Did you read Documentation/i2c/writing-clients?

> So here “list_for_each(item,&adapters)” returns FALSE for me. So my attach
> adapter function, “i2c_test_attach_adapter()” is not getting called.

Probing should be done by setting i2c_board_info from your board support
code - also described in Documentation/i2c/writing-clients.

> 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?

You're digging too much through the core code. It works well for others,
so debugging this part is not the first thing you should consider. Best
thing is probably to grab an existing driver and see how it does the
job.

Daniel