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

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Mar 05, 2025 at 09:46:16AM -0300, Filipe Xavier wrote:
> On 3/4/25 11:09 AM, Greg KH wrote:
> 
> > On Tue, Mar 04, 2025 at 09:55:11AM -0300, Filipe Xavier 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>
> > > ---
> > >   rust/kernel/bitmask.rs | 171 +++++++++++++++++++++++++++++++++++++++++++++++++
> > >   rust/kernel/lib.rs     |   2 +
> > >   rust/kernel/prelude.rs |   1 +
> > >   3 files changed, 174 insertions(+)
> > > 
> > > diff --git a/rust/kernel/bitmask.rs b/rust/kernel/bitmask.rs
> > > new file mode 100644
> > > index 0000000000000000000000000000000000000000..8d26a541c693a2cb60096059ecb708d895bb3ad1
> > > --- /dev/null
> > > +++ b/rust/kernel/bitmask.rs
> > > @@ -0,0 +1,171 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +
> > > +//! Bitmask utilities for working with flags in Rust.
> > > +
> > > +/// Declares a bitmask type with its corresponding flag type.
> > > +///
> > > +/// This macro generates:
> > > +/// - Implementations of common bitwise operations (`BitOr`, `BitAnd`, etc.).
> > > +/// - Utility methods such as `.contains()` to check flags.
> > > +///
> > > +/// # Examples
> > > +///
> > > +/// Defining and using a bitmask:
> > > +/// ```
> > > +/// bitmask!(Permissions, Permission, u32);
> > Nice, but why not use the same api/names that are already in the kernel
> > for this type of functionality in the C .h files?  That way we have
> > consistent names everywhere?
> > 
> > thanks,
> > 
> > greg k-h
> 
> Makes sense, my mistake, I didn't know...
> Could you send me the reference of what already exists in the kernel so I
> can change it?

Look in include/linux/bit*