Preprocessor arithmetic in dtsi files (base + offset)

[Geert Uytterhoeven]

On Thu, Nov 26, 2015 at 3:44 PM, Mason <slash.tmp at free.fr> wrote:
> On 26/11/2015 14:59, Russell King - ARM Linux wrote:
>> On Thu, Nov 26, 2015 at 02:16:16PM +0100, Mason wrote:
>>> #define SCU_BASE 0x20000000
>>>
>>>      scu: scu at XXX {
>>>              compatible = "arm,cortex-a9-scu";
>>>              reg = <SCU_BASE 0x100>;
>>>
>>>      gic: interrupt-controller at XXX {
>>>              compatible = "arm,cortex-a9-gic";
>>>              reg = <SCU_BASE+0x1000 0x1000>, <SCU_BASE+0x100 0x0100>;
>>
>> You don't get preprocessor arithmetic here.  What you get is this passed
>> to DTC:
>>
>>               reg = <0x20000000+0x1000 0x1000>...
>>
>> The only time the preprocessor does arithmetic is when it needs to
>> evaluate an expression, eg, in an #if statement.
>
> Doh! Brain malfunction. No arithmetic indeed.
> Working with the preprocessor would have to involve token-pasting.
>
> #define SCU_BASE(OFFSET)        2000##OFFSET
> #define SCU_BASEX(OFFSET)       0x2000##OFFSET
>
>         gic: interrupt-controller at SCU_BASE(1000) {
>                 reg = <SCU_BASEX(1000) 0x1000>, <SCU_BASEX(0100) 0x0100>;
>         };
>
> My very own abomination!

Yeah! ;-)

I guess this would work, too?

scu_container at 20000000 {
        compatible = "simple-bus";

        ranges = <0x0 0x20000000 0x10000>;
        #address-cells = <1>;
        #size-cells = <1>;

        scu: scu at 0 {
                compatible = "arm,cortex-a9-scu";
                reg = <0x0000 0x100>;

        gic: interrupt-controller at 1000 {
                compatible = "arm,cortex-a9-gic";
                reg = <0x1000 0x1000>, <0x0100 0x0100>;

        twd-timer at 0600 {
                compatible = "arm,cortex-a9-twd-timer";
                reg = <0x0600 0x10>;
};

No more explicit arithmetic needed, just substitue "20000000".

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds