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Message-Id: <20251026-feat-add-bitmask-macro-v4-1-e1b59b4762bc@gmail.com>
Date: Sun, 26 Oct 2025 09:16:15 -0300
From: Filipe Xavier <felipeaggger@...il.com>
To: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Benno Lossin <benno.lossin@...ton.me>,
Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>,
Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>
Cc: daniel.almeida@...labora.com, rust-for-linux@...r.kernel.org,
felipe_life@...e.com, linux-kernel@...r.kernel.org,
Filipe Xavier <felipeaggger@...il.com>, Lyude Paul <lyude@...hat.com>
Subject: [PATCH v4] rust: add new macro for common bitmap operations
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
Signed-off-by: Filipe Xavier <felipeaggger@...il.com>
Suggested-by: Daniel Almeida <daniel.almeida@...labora.com>
Suggested-by: Lyude Paul <lyude@...hat.com>
---
Changes in v4:
- Use enum: changed flag type from struct to enum.
- Minor fix: airect casting (flag as $ty) instead of field access (.0).
- Link to v3: https://lore.kernel.org/r/20250411-feat-add-bitmask-macro-v3-1-187bd3e4a03e@gmail.com
Changes in v3:
- New Feat: added support to declare flags inside macro use.
- Minor fixes: used absolute paths to refer to items, fix rustdoc and fix example cases.
- Link to v2: https://lore.kernel.org/r/20250325-feat-add-bitmask-macro-v2-1-d3beabdad90f@gmail.com
Changes in v2:
- rename: change macro and file name to impl_flags.
- negation sign: change char for negation to `!`.
- transpose docs: add support to transpose user provided docs.
- visibility: add support to use user defined visibility.
- operations: add new operations for flag,
to support use between bit and bitmap, eg: flag & flags.
- code style: small fixes to remove warnings.
- Link to v1: https://lore.kernel.org/r/20250304-feat-add-bitmask-macro-v1-1-1c2d2bcb476b@gmail.com
---
rust/kernel/impl_flags.rs | 227 ++++++++++++++++++++++++++++++++++++++++++++++
rust/kernel/lib.rs | 1 +
rust/kernel/prelude.rs | 1 +
3 files changed, 229 insertions(+)
diff --git a/rust/kernel/impl_flags.rs b/rust/kernel/impl_flags.rs
new file mode 100644
index 0000000000000000000000000000000000000000..15c8fc82e76254f927b7487379d8f0a2776a4010
--- /dev/null
+++ b/rust/kernel/impl_flags.rs
@@ -0,0 +1,227 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/// Declares a impl_flags type with its corresponding flag type.
+///
+/// This macro generates:
+/// - Implementations of common bitmap op. ([`::core::ops::BitOr`], [`::core::ops::BitAnd`], etc.).
+/// - Utility methods such as `.contains()` to check flags.
+///
+/// # Examples
+///
+/// Defining and using impl_flags:
+///
+/// ```
+/// use kernel::impl_flags;
+///
+/// impl_flags!(
+/// /// Represents multiple permissions.
+/// #[derive(Debug, Clone, Default, Copy, PartialEq, Eq)]
+/// pub struct Permissions(u32);
+/// /// Represents a single permission.
+/// #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+/// pub enum Permission {
+/// Read = 1 << 0,
+/// Write = 1 << 1,
+/// Execute = 1 << 2,
+/// }
+/// );
+///
+/// // Combine multiple permissions using operation OR (`|`).
+/// let read_write: Permissions = Permission::Read | Permission::Write;
+///
+/// assert!(read_write.contains(Permission::Read));
+/// assert!(read_write.contains(Permission::Write));
+/// assert!(!read_write.contains(Permission::Execute));
+///
+/// // Removing a permission with operation AND (`&`).
+/// let read_only: Permissions = read_write & Permission::Read;
+/// assert!(read_only.contains(Permission::Read));
+/// assert!(!read_only.contains(Permission::Write));
+///
+/// // Toggling permissions with XOR (`^`).
+/// let toggled: Permissions = read_only ^ Permission::Read;
+/// assert!(!toggled.contains(Permission::Read));
+///
+/// // Inverting permissions with negation (`!`).
+/// let negated = !read_only;
+/// assert!(negated.contains(Permission::Write));
+/// ```
+#[macro_export]
+macro_rules! impl_flags {
+ (
+ $(#[$outer_flags:meta])*
+ $vis_flags:vis struct $flags:ident($ty:ty);
+
+ $(#[$outer_flag:meta])*
+ $vis_flag:vis enum $flag:ident {
+ $(
+ $(#[$inner_flag:meta])*
+ $name:ident = $value:expr
+ ),+ $( , )?
+ }
+ ) => {
+ $(#[$outer_flags])*
+ #[repr(transparent)]
+ $vis_flags struct $flags($ty);
+
+ $(#[$outer_flag])*
+ #[repr($ty)]
+ $vis_flag enum $flag {
+ $(
+ $(#[$inner_flag])*
+ $name = $value
+ ),+
+ }
+
+ impl ::core::convert::From<$flag> for $flags {
+ #[inline]
+ fn from(value: $flag) -> Self {
+ Self(value as $ty)
+ }
+ }
+
+ impl ::core::convert::From<$flags> for $ty {
+ #[inline]
+ fn from(value: $flags) -> Self {
+ value.0
+ }
+ }
+
+ impl ::core::ops::BitOr for $flags {
+ type Output = Self;
+ #[inline]
+ fn bitor(self, rhs: Self) -> Self::Output {
+ Self(self.0 | rhs.0)
+ }
+ }
+
+ impl ::core::ops::BitOrAssign for $flags {
+ #[inline]
+ fn bitor_assign(&mut self, rhs: Self) {
+ *self = *self | rhs;
+ }
+ }
+
+ impl ::core::ops::BitAnd for $flags {
+ type Output = Self;
+ #[inline]
+ fn bitand(self, rhs: Self) -> Self::Output {
+ Self(self.0 & rhs.0)
+ }
+ }
+
+ impl ::core::ops::BitAndAssign for $flags {
+ #[inline]
+ fn bitand_assign(&mut self, rhs: Self) {
+ *self = *self & rhs;
+ }
+ }
+
+ impl ::core::ops::BitOr<$flag> for $flags {
+ type Output = Self;
+ #[inline]
+ fn bitor(self, rhs: $flag) -> Self::Output {
+ self | Self::from(rhs)
+ }
+ }
+
+ impl ::core::ops::BitOrAssign<$flag> for $flags {
+ #[inline]
+ fn bitor_assign(&mut self, rhs: $flag) {
+ *self = *self | rhs;
+ }
+ }
+
+ impl ::core::ops::BitAnd<$flag> for $flags {
+ type Output = Self;
+ #[inline]
+ fn bitand(self, rhs: $flag) -> Self::Output {
+ self & Self::from(rhs)
+ }
+ }
+
+ impl ::core::ops::BitAndAssign<$flag> for $flags {
+ #[inline]
+ fn bitand_assign(&mut self, rhs: $flag) {
+ *self = *self & rhs;
+ }
+ }
+
+ impl ::core::ops::BitXor for $flags {
+ type Output = Self;
+ #[inline]
+ fn bitxor(self, rhs: Self) -> Self::Output {
+ Self(self.0 ^ rhs.0)
+ }
+ }
+
+ impl ::core::ops::BitXorAssign for $flags {
+ #[inline]
+ fn bitxor_assign(&mut self, rhs: Self) {
+ *self = *self ^ rhs;
+ }
+ }
+
+ impl ::core::ops::Not for $flags {
+ type Output = Self;
+ #[inline]
+ fn not(self) -> Self::Output {
+ Self(!self.0)
+ }
+ }
+
+ impl ::core::ops::BitOr for $flag {
+ type Output = $flags;
+ #[inline]
+ fn bitor(self, rhs: Self) -> Self::Output {
+ $flags(self as $ty | rhs as $ty)
+ }
+ }
+
+ impl ::core::ops::BitAnd for $flag {
+ type Output = $flags;
+ #[inline]
+ fn bitand(self, rhs: Self) -> Self::Output {
+ $flags(self as $ty & rhs as $ty)
+ }
+ }
+
+ impl ::core::ops::BitXor for $flag {
+ type Output = $flags;
+ #[inline]
+ fn bitxor(self, rhs: Self) -> Self::Output {
+ $flags(self as $ty ^ rhs as $ty)
+ }
+ }
+
+ impl ::core::ops::Not for $flag {
+ type Output = $flags;
+ #[inline]
+ fn not(self) -> Self::Output {
+ $flags(!(self as $ty))
+ }
+ }
+
+ impl ::core::ops::BitXor<$flag> for $flags {
+ type Output = Self;
+ #[inline]
+ fn bitxor(self, rhs: $flag) -> Self::Output {
+ self ^ Self::from(rhs)
+ }
+ }
+
+ impl $flags {
+ /// Returns an empty instance of `type` where no flags are set.
+ #[inline]
+ pub const fn empty() -> Self {
+ Self(0)
+ }
+
+ /// Checks if a specific flag is set.
+ #[inline]
+ pub fn contains(self, flag: $flag) -> bool {
+ (self.0 & flag as $ty) == flag as $ty
+ }
+ }
+ };
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 28007be98fbad0e875d7e5345e164e2af2c5da32..a315607629c321db377343ca678c9845ae69bb14 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -67,6 +67,7 @@
#[cfg(CONFIG_RUST_FW_LOADER_ABSTRACTIONS)]
pub mod firmware;
pub mod fs;
+pub mod impl_flags;
pub mod init;
pub mod io;
pub mod ioctl;
diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs
index baa774a351ceeb995a2a647f78a27b408d9f3834..085f23502544c80c2202eacd18ba190186a74f30 100644
--- a/rust/kernel/prelude.rs
+++ b/rust/kernel/prelude.rs
@@ -27,6 +27,7 @@
#[doc(no_inline)]
pub use super::dbg;
pub use super::fmt;
+pub use super::impl_flags;
pub use super::{dev_alert, dev_crit, dev_dbg, dev_emerg, dev_err, dev_info, dev_notice, dev_warn};
pub use super::{pr_alert, pr_crit, pr_debug, pr_emerg, pr_err, pr_info, pr_notice, pr_warn};
---
base-commit: edc5e6e019c99b529b3d1f2801d5cce9924ae79b
change-id: 20250304-feat-add-bitmask-macro-6424b1c317e2
Best regards,
--
Filipe Xavier <felipeaggger@...il.com>
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