Devicetree spec: Specifying /cpus/cpu@* unit address format?

[Vivian Wang]

On 4/6/26 20:48, Rob Herring wrote:
> On Sat, Apr 4, 2026 at 11:43 PM David Gibson
> <david at gibson.dropbear.id.au> wrote:
>> On Fri, Apr 03, 2026 at 06:06:17PM +0800, Vivian Wang wrote:
>>> (Also posted at: https://github.com/devicetree-org/devicetree-specification/issues/86 )
>>>
>>> Hi all,
>>>
>>> Presently, there seems to be some confusion in the community about the
>>> format of unit addresses for "/cpus/cpu@*" nodes for a CPU with ID > 9, e.g.
>>>
>>>     cpu@??? {
>>>         reg = <10>;
>>>         /* reg = <0xa>; */ /* This should be equivalent */
>>>     }
>>>
>>>
>>> Should this be a decimal "cpu at 10", or hexadecimal "cpu at a"? I can't find
>>> any explicit specification.
>> It should be hex.  That's a general convention for unit addresses.
>> Before flattened trees, OF essentially never used decimal
>> representations of things.
> The only decimal usage in FDT were mistakes.

Thanks for this. This is clear enough for me.

> Rather than worrying about what the spec says, please worry about what
> the tools check.

Since, as you two said, there is an established convention, I agree that
convention is enough here.

Thanks,
Vivian "dramforever" Wang