On Wed, Jan 4, 2012 at 1:00 PM, Stephen Warren <swarren@xxxxxxxxxx> 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. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
