Re: [PATCH] rust: add new macro for common bitwise operations

[Lyude Paul <lyude@redhat.com>]

On Tue, 2025-03-04 at 13:57 +0100, Alice Ryhl wrote:
> On Tue, Mar 4, 2025 at 1:55 PM Filipe Xavier <felipeaggger@gmail.com> wrote:
> > 
> > We have seen a proliferation of mod_whatever::foo::Flags
> > being defined with essentially the same implementation
> > for bitAnd, bitOr, contains and etc.
> > 
> > This macro aims to bring a solution for this,
> > allowing to generate these methods for user-defined structs.
> > With some use cases in KMS and VideoCodecs.
> > 
> > Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/topic/We.20really.20need.20a.20common.20.60Flags.60.20type
> > Signed-off-by: Filipe Xavier <felipeaggger@gmail.com>
> 
> Hmm. I wonder about having all of the bitwise operations. Most of the
> time, I would only want the || operator, and maybe also &&. That way,
> it's guaranteed that you can never get a Flags with an unknown bit
> set, which might be useful for soundness.

FWIW: The reason I had suggested that we have a split of Flag and Flags type
was because I wanted to make sure that we could potentially handle unknown
flags transparently. I'm not sure how flags with only || or && would be that
useful, needing to do bitwise and/or is extremely common. Being able to handle
unknown flags would be good as well for bindings where we don't really care
about all of the flags in a bitmask but explicitly want to enable one or two
specific flags without changing the state of the rest of the bitmask.


> 
> Alice

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat

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