Help Regarding I2C Driver...

Help Regarding I2C Driver...

[Uma Kanta Patro]

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

Re: Help Regarding I2C Driver...

[Daniel Mack]

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

RE: Help Regarding I2C Driver...

[Uma Kanta]

Hi Daniel,
	Thanks for your reply..

> >                 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.

Yaa, this version is very old, but as currently I have to develop for
this version  for our project so I have to try developing in this
version itself.

>
> > 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?

Can you please tell me what may be the alternative option for
"attach_adapter"
Field of i2c_driver. Also I read the documentation in
Documentation/i2c/writing-clients of Linux 2.6.19. Also I made my code
in the same way as the examples in drivers/i2c/chips/. But I am not
having th effect.

>
> > 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.

Actually in Linux 2.6.19 I feel that there is no provisions for
i2c_board_info,  as non of the existing chip drivers such as eeprom,
RTCs don't have any i2c_board_info structure in the file
arch\arm\mach-at91rm9200\board-ek.c.
Also in this version the function, "at91_add_device_i2c()" does not
accept arguments  whereas in the advanced versions it takes two
arguments such as object of structure i2c_board_info and its size.
So what may be the alternative of i2c_board_info in case of Linux
2.6.19?
Is it possible to work with I2C in  Linux 2.6.19???
>
> > 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.
Actually I wanted to know where I was lagging. But now as previously I
mentioned I am not able to get the I2C working for my driver.
One more thing as I am doing for ARM platform,I wanted to know the
significance of the bus driver i2c-at91.
Do I need to take care of that to create my chip driver?


Thanks for the patience...

With Regards,
Uma Kanta Patro

Re: Help Regarding I2C Driver...

[Daniel Mack]

Hi,

On Tue, Mar 24, 2009 at 11:06:51AM +0530, Uma Kanta wrote:
> > This version is ancient, you should consider updating to something 
> > more recent.
> 
> Yaa, this version is very old, but as currently I have to develop for
> this version  for our project so I have to try developing in this
> version itself.

[...]

> > Probing should be done by setting i2c_board_info from your board 
> > support code - also described in Documentation/i2c/writing-clients.
> 
> Actually in Linux 2.6.19 I feel that there is no provisions for
> i2c_board_info,  as non of the existing chip drivers such as eeprom,
> RTCs don't have any i2c_board_info structure in the file
> arch\arm\mach-at91rm9200\board-ek.c.
> Also in this version the function, "at91_add_device_i2c()" does not
> accept arguments  whereas in the advanced versions it takes two
> arguments such as object of structure i2c_board_info and its size.
> So what may be the alternative of i2c_board_info in case of Linux
> 2.6.19?
> Is it possible to work with I2C in  Linux 2.6.19???

Sorry, I don't know much about this legacy. I was just writing a driver
for an I2C connected device and thought I could point you in the right
direction, but that was all on cutting edge git trees. Maybe someone
else can help.

But in general, you should be able to base your work on drivers that are
there in the tree already and more or less copy their approach. It is
definitely possible to use I2C with your kernel version.

Daniel