Re: [PATCH V2 03/10] pinctrl: exynos: add exynos5260 SoC specific data

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On 07.01.2014 14:31, Arnd Bergmann wrote:
On Tuesday 07 January 2014 18:29:01 Rahul Sharma wrote:
From: Young-Gun Jang <yg1004.jang@xxxxxxxxxxx>

Add Samsung Exynos5260 SoC specific data to enable pinctrl
support for all platforms based on EXYNOS5260.

Signed-off-by: Pankaj Dubey <pankaj.dubey@xxxxxxxxxxx>
Signed-off-by: Young-Gun Jang <yg1004.jang@xxxxxxxxxxx>
Signed-off-by: Rahul Sharma <rahul.sharma@xxxxxxxxxxx>
Signed-off-by: Arun Kumar K <arun.kk@xxxxxxxxxxx>

On a similar note to the comment about the platform patch, I think
it would be good to extend the DT binding in a way that allows
you to describe the differences between the SoCs without having
to change the driver every time a new model comes out.

We still have to maintain backwards compatibility with the
existing bindings I suppose, but I'd rather not see new ones
added like this. I realize that there is a tradeoff between
having too much information in DT when it is always fixed, and
having too much hardcoded in the driver, and at some point there
was a conscious decision to do it like this, but I fear the
tradeoff has changed with the number of EXYNOS implementations
that really only differ in their pin banks.

There isn't really too much data being added to the driver on per-SoC basis. Anyway, I remember that when I was trying to move all the data to DT long time ago when refactoring the driver, after a long discussion on the ML it was decided that it is not really a good idea and so we have the end result as we can see now.

Personally I'd prefer all the static data of struct samsung_pin_bank to be located in DT, with each bank having a compatible string that would translate to appropriate struct samsung_pin_bank_type, which is common across multiple SoCs (basically all >= S5PV210), and parameters such as pin-count, control-base, and geint-/weint-base (which would also imply interrupt type) - name (which is used only for human readable text) could be implied by node names. However that would mean quite significant effort (and churn), especially considering the fact that we need to maintain compatibility with existing bindings, due to "ABI stability" (which I'm slowly losing my faith in), so I don't think it's worth it.

So, from me:

Acked-by: Tomasz Figa <t.figa@xxxxxxxxxxx>

Best regards,
Tomasz
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