On Fri, 2014-11-07 at 17:33 +0200, Ivan T. Ivanov wrote:

On Thu, 2014-11-06 at 08:55 -0800, Bjorn Andersson wrote:

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On Wed, Nov 5, 2014 at 11:54 PM, Ivan T. Ivanov [off-list ref] wrote:

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On Wed, 2014-11-05 at 17:36 -0800, Bjorn Andersson wrote:

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On Wed, Nov 5, 2014 at 10:31 AM, Ivan T. Ivanov [off-list ref] wrote:

[..]

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Some of the child device drivers have to know PMIC chip revision.

So your plan is to have a strstr(parent->compatible, "-v2") there?

Actually also PMIC subtype (pm8841, pm8226...) is also required, so
the plan is to have something like this:

{
        static const struct of_device_id pmic_match_table[] = {
                { .compatible = "qcom,pm8941-v1.0" },
                { .compatible = "qcom,pm8841-v0.0" },
                { }

        };

        const struct of_device_id *match;

        match = of_match_device(pmic_match_table, pdev->dev.parent);
        if (match) {
                dev_info(&pdev->dev, "%s chip detected\n", match->compatible);
        }
}

To me this is a hack, you should not alter the devicetree to make it
"better express the hardware". Either you know these things from boot
and they go in device tree, or you can probe them and they should not
go in device tree.

If you really need these values you should expose them through some api.

I would like to avoid compile time dependency between these drivers.
There are several precedents of using of_update_property() for enhancing
compatible property already.

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Could you be a little bit more elaborate on what you're trying to do
and which child devices that might be?

For example ADC drivers are required temperature compensation based
on PMIC variant and chip manufacturer.

I see, is that compensation of any practical value? Or is the
compensation of academic proportions?

It depends of what you mean by academic :-). Attached file have test
application which dump difference between non compensated and compensated
values for different temperature, manufacture and input value.

Output format of the program is:
Column 1: manufacturer GF=0, SMIC=1, TSMC=2
Column 2: chip revision
Column 3: die temperature in mili deg Celsius
Column 4: input for compensation in micro Volts
Column 5: compensated result in micro Volts
Column 6: difference in micro Volts

Forgot to add. PMIC subtype and version are used also in charger and BMS
drivers to workaround hardware issues.

Ivan