Re: [PATCH v2 07/13] dt-bindings: riscv: Add B ISA extension description

[Alex Elder <elder@riscstar.com>]

On 12/27/25 8:51 PM, Guodong Xu wrote:
>> That's what I understand it to mean, anyway.
>>     https://github.com/riscv/riscv-b
>>
>> There's no point in supporting "b" in devicetree to represent
>> the others if it also requires the others to be present.
>>
>> I think that, instead, "b", "zba", "zbb", and "zbs" should all
>> be allowed.
>>
>> I might even go further and harden the requirement, saying that
>> if you specify "b" you should*not* specify "zba", "zbb", or "zbs".
> Historical reasons here. "b" came too late. The chip vendors have published
> cores with "zba", "zbb", and "zbs"already.
> 
> That's a migration bridge to require "b" must be listed
> together with the other three.

Are you saying "b" has already been included with "zba", "zbb", and
"zbs" in an existing DTS file?

What I'm suggesting is that (unless someone has already done this in
a DTS file), there is no reason to require "b" *and* the other three.
You should allow either "b" *or* all of the other three, not both.
That would support older platforms as well as newer ones that use
the more concise "b" only.

					-Alex