Messages in this thread |  | | Date | Fri, 6 Mar 2026 13:04:02 -0600 | | From | Andrew Jones <> | | Subject | Re: [RFC PATCH v1 04/11] riscv: Add B to hwcap |
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On Fri, Mar 06, 2026 at 06:50:20PM +0000, Conor Dooley wrote: > On Fri, Mar 06, 2026 at 12:27:50PM -0600, Andrew Jones wrote: > > On Fri, Mar 06, 2026 at 10:17:19AM +0800, Guodong Xu wrote: > > > > + /* > > > + * B is functionally a bundle (Zba + Zbb + Zbs, > > > + * no additional instructions). We use SUPERSET > > > + * instead of BUNDLE because B needs a valid ext > > > + * id for isa2hwcap[] to set COMPAT_HWCAP_ISA_B. > > What's the actual rationale for it working like that? > Why shouldn't bundles appear in cpuinfo etc, I forget entirely why we > did it this way. Feels like it'd be easier for users, no? > > 2023 me might disagree, but 2026 me doesn't see the value in hiding these > extensions. All I can think of was me being very negative, and hedging > against bad software checking for zkn and not checking for the subsets, > and breaking if the dt listed the entire subset but not zkn. That, or > not wanting to implement code that looked for subset extensions and > populated the relevant bundle if the bundle itself was missing but all > components were there.
I also can't remember and the 2026 me doesn't want to google 2023 me's thoughts. I think we may have opted not to publish bundles because we didn't believe publishing them would help reduce much confusion, as the concept of a bundle itself was a bit confusing...
Thanks, drew
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