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From: Andreas Hindborg <a.hindborg@kernel.org>
To: Filipe Xavier <felipeaggger@gmail.com>, Miguel Ojeda <ojeda@kernel.org>,
 Alex Gaynor <alex.gaynor@gmail.com>, Boqun Feng <boqun.feng@gmail.com>,
 Gary Guo <gary@garyguo.net>, =?utf-8?Q?Bj=C3=B6rn?= Roy Baron
 <bjorn3_gh@protonmail.com>,
 Benno Lossin <benno.lossin@proton.me>, Alice Ryhl <aliceryhl@google.com>,
 Trevor Gross <tmgross@umich.edu>, Danilo
 Krummrich <dakr@kernel.org>
Cc: daniel.almeida@collabora.com, rust-for-linux@vger.kernel.org,
 felipe_life@live.com, linux-kernel@vger.kernel.org, Lyude Paul
 <lyude@redhat.com>, Filipe Xavier <felipeaggger@gmail.com>
Subject: Re: [PATCH v8] rust: add new macro for common bitflag operations
In-Reply-To: <87jyxjf56j.fsf@kernel.org>
References: <2JpjX5S1c2QLiHUftMzVViS7xatVGkJperCPqxJU8ZQ_Opyo4KPge5jcRCPb0Gcgyxb4yeFhm6Y-1X8q3pbNaw==@protonmail.internalid>
 <20260111-feat-add-bitmask-macro-v8-1-3bc0a558ede0@gmail.com>
 <87jyxjf56j.fsf@kernel.org>
Date: Thu, 15 Jan 2026 13:14:36 +0100
Message-ID: <87h5snf4yb.fsf@kernel.org>
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Andreas Hindborg <a.hindborg@kernel.org> writes:

> "Filipe Xavier" <felipeaggger@gmail.com> writes:
>
>> 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 upcoming GPU drivers.
>>
>> Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/topic/We.20really.20need.20a.20common.20.60Flags.60.20type
>> Suggested-by: Daniel Almeida <daniel.almeida@collabora.com>
>> Suggested-by: Lyude Paul <lyude@redhat.com>
>> Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
>> Reviewed-by: Lyude Paul <lyude@redhat.com>
>> Signed-off-by: Filipe Xavier <felipeaggger@gmail.com>
>
> Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
> Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
>
>
> I think it would be useful to add:
>
> impl Flags {
>      unsafe from_raw(value: Repr) -> {
>      ...
>      }
> }
>
> impl TryFrom<Repr> for Flag {
>      // Succeed if `value` is a valid `Flag` enum bit pattern.
> }
>
> impl TryFrom<Repr> for Flags {
>      // Succeed if `value` is the logical OR of valid enum bit patterns.
> }

Also bitwise operations on the underlying type such as

  impl BitOrAssign<Flag> for u32 {
  ...
  }

Not sure if that is possible with the orphan rule, but it would be nice.
I was trying to

  lim.features |= request::Feature::Rotational;

where `lim: bindings::queue_limits`.


Best regards,
Andreas Hindborg