How to pass board specific info to I2C driver module

Question

Hi All,

I'm working on an ADC chip (MCP3021) driver under Linux 2.6.27.
We used these two chips to monitor the CPU core current and
platform current individually, which is converted to voltage as
the ADC chip's input.
As you know, the driver shouldn't contain the board specific info,
such as, the chip's work voltage, the ratio of voltage and current.
So how to pass these info to the driver module?

Here is the way I can think of:
1. to use dts file to pass the info to the module.
    This way make the driver is bound to OF implement.

2. to use the module parameter.
    For different chips, the work voltage and the ratio may be different,
    but the chip uses the same driver.

Any other idea? Please give me some advice. Thanks a lot.

Answer 1

Your question is that how the kernel space to communicate with the userspace?
If so, I suggest you read some articles on the website of IBM developer.

Answer 2

Thanks for you reply.

It doesn't matter. I just want to make it to be a general driver.
So I must handle the individual parameter of the different chips in the driver.

Answer 3

Your application is very special
I wish you can share your design and ideas.

Answer 4

I do not think the methods you mentioned are good enough, for example, if you pass a module parameter to your module, and it is initialized using this parameter, how do you differentiate your Vdds?

I suggest that you could use the parameters when you call ioctl/read, you can define a struct like this:
struct para
{
    int vdd;//in mini V
    int vin; // in mini V
};

then when you call ioctl, first assign the vdd to para, then the driver can read the value back and do the trans, return the vin back to your application.

using this way, your driver can deal with all kinds of Vdds, right?

Answer 5

Good suggestion!
But I really don't quite understand what his real attempt!

Answer 6

First thanks for you guys reply.

yeah, bluesky_jxc's method will work, but the question is that
we don't write the application, the user get the voltage info through
sysfs or lm-sensors tool.

so far, I just pass the vdd info to driver through module parameter or
kernel parameter(if builtin), and give the voltage info through sysfs
(lm-sensors tool also can get the info).

Answer 7

I don't think so.....

How can different modules with different Vdds share your driver if you use the
module parameter? if one uses Vdd=2.5V and the other uses Vdd=1.8V, how can
you tell the driver when to use 2.5 or 1.8?

Please take care, because your driver may be used for many chips with different
Vdds, not  just the one you are using now .

Answer 8

yes, there is an assumption. Generally, it's all 3.3V.

It's a little weird and hard issue for hw engineer that
the same type chip on the same bus uses different Vdd.

Answer 9

Provide mechanism, not policy, if you want to provide a good driver.
But if you just want to make it work, any way will be OK