[PATCH 6/6] gpio: tegra: Parameterize the number of banks

[Grant Likely]

On Wed, Jan 4, 2012 at 1:00 PM, Stephen Warren <swarren at nvidia.com> wrote:
> Rob Herring wrote at Wednesday, January 04, 2012 12:54 PM:
>> On 01/04/2012 12:39 PM, Stephen Warren wrote:
>> > Tegra20's GPIO controller has 7 banks, and Tegra30's controller has 8
>> > banks. Allow the number of banks to be configured at run-time by the
>> > device tree.
> ...
>> > diff --git a/Documentation/devicetree/bindings/gpio/gpio_nvidia.txt
> ...
>> >  Required properties:
>> >  - compatible : "nvidia,tegra20-gpio"
>> >  - reg : Physical base address and length of the controller's registers.
>> > +- nvidia,num-banks : The number of GPIO banks. This should be 7 for
>> > +  Tegra20 and 8 for Tegra30. This must match the number of interrupt
>> > +  specifiers in the interrupts property.
>>
>> You can determine the number of banks based on the compatible property
>> rather than needing an additional property.
>
> That's certainly possible.
>
> However, if say nvidia,tegraNNN-gpio has 9 banks, we then have to
> explicitly edit the driver to know that, whereas by using a property,
> we wouldn't have to change the driver at all to support a future GPIO
> controller. So, isn't it better to explicitly represent this in DT?
>
> Note that I have no idea how many GPIO banks our future chips will have,
> so this might not turn out to save any work at all, but perhaps.

It's an engineering/design decision that requires taste and instinct.
Either approach is fine, you decide which one will be the best in the
long term.

g.