Re: [PATCH v8 01/11] riscv: Add B to hwcap and hwprobe

[Radim Krcmar]

2026-10-02T05:22:41-04:00, Guodong Xu <guodong.xu@xxxxxxxxxxxxxxxx>:
> On Tue, 29 Sep 2026 15:12:36 +0000, Radim Krcmar wrote:
>> Are we sure that B will always be listed in the ISA string when Zba,
>> Zbb, and Zbs are present?
>
> For DT, yes. The binding requires b whenever zba, zbb and zbs are
> listed, since commit 0cdb7fc1879b ("dt-bindings: riscv: Add B ISA
> extension description").
>
> For ACPI there is no such check. But B is a ratified RVI extension
> and RVA23U64 lists it as mandatory [1], so any serious hardware vendor
> should respect it. Right?
>
> If the firmware does not advertise B, why should the kernel correct that
> for them? This came up in v2 [2], and maybe here I should quote what Conor
> said in [3], which I agree with:
>
> " Part of me wants to know why we should be going to a bunch of effort
>   to cover up for inaccurate devicetrees etc. Garbage in -> garbage out
>   and let them keep the pieces."

Great arguments, sorry that I didn't read the older discussions...

Reviewed-by: Radim Krčmář <radim.krcmar@xxxxxxxxxxxxxxxx>