[PATCH v4 4/6] rust: Move register and bitfield macros out of Nova

Joel Fernandes
2025-09-20T18:23:20Z

Out of broad need for these macros in Rust, move them out. Several folks
have shown interest (Nova, Tyr GPU drivers).

bitfield moved into bits modules - defines bitfields in Rust structs similar to C.
register moved into io module - defines hardware registers and accessors.

Reviewed-by: Elle Rhumsaa <elle@weathered-steel.dev>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
---
MAINTAINERS | 1 +
drivers/gpu/nova-core/falcon.rs | 2 +-
drivers/gpu/nova-core/falcon/gsp.rs | 4 +-
drivers/gpu/nova-core/falcon/sec2.rs | 2 +-
drivers/gpu/nova-core/nova_core.rs | 3 --
drivers/gpu/nova-core/regs.rs | 6 +--
rust/kernel/bits.rs | 2 +
.../kernel/bits}/bitfield.rs | 27 ++++++-----
rust/kernel/io.rs | 1 +
.../macros.rs => rust/kernel/io/register.rs | 46 ++++++++++---------
10 files changed, 51 insertions(+), 43 deletions(-)
rename {drivers/gpu/nova-core => rust/kernel/bits}/bitfield.rs (91%)
rename drivers/gpu/nova-core/regs/macros.rs => rust/kernel/io/register.rs (93%)

diff --git a/MAINTAINERS b/MAINTAINERS
index 841b76234045..a94af8607b6b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4379,6 +4379,7 @@ F: include/asm-generic/bitops.h
F: include/linux/bitops.h
F: lib/test_bitops.c
F: tools/*/bitops*
+F: rust/kernel/bits*

BITOPS API BINDINGS [RUST]
M: Yury Norov <yury.norov@gmail.com>
diff --git a/drivers/gpu/nova-core/falcon.rs b/drivers/gpu/nova-core/falcon.rs
index 37e6298195e4..a15fa98c8614 100644
--- a/drivers/gpu/nova-core/falcon.rs
+++ b/drivers/gpu/nova-core/falcon.rs
@@ -6,6 +6,7 @@
use hal::FalconHal;
use kernel::device;
use kernel::dma::DmaAddress;
+use kernel::io::register::RegisterBase;
use kernel::prelude::*;
use kernel::sync::aref::ARef;
use kernel::time::Delta;
@@ -14,7 +15,6 @@
use crate::driver::Bar0;
use crate::gpu::Chipset;
use crate::regs;
-use crate::regs::macros::RegisterBase;
use crate::util;

pub(crate) mod gsp;
diff --git a/drivers/gpu/nova-core/falcon/gsp.rs b/drivers/gpu/nova-core/falcon/gsp.rs
index f17599cb49fa..cd4960e997c8 100644
--- a/drivers/gpu/nova-core/falcon/gsp.rs
+++ b/drivers/gpu/nova-core/falcon/gsp.rs
@@ -1,9 +1,11 @@
// SPDX-License-Identifier: GPL-2.0

+use kernel::io::register::RegisterBase;
+
use crate::{
driver::Bar0,
falcon::{Falcon, FalconEngine, PFalcon2Base, PFalconBase},
- regs::{self, macros::RegisterBase},
+ regs::self,
};

/// Type specifying the `Gsp` falcon engine. Cannot be instantiated.
diff --git a/drivers/gpu/nova-core/falcon/sec2.rs b/drivers/gpu/nova-core/falcon/sec2.rs
index 815786c8480d..81717868a8a8 100644
--- a/drivers/gpu/nova-core/falcon/sec2.rs
+++ b/drivers/gpu/nova-core/falcon/sec2.rs
@@ -1,7 +1,7 @@
// SPDX-License-Identifier: GPL-2.0

use crate::falcon::{FalconEngine, PFalcon2Base, PFalconBase};
-use crate::regs::macros::RegisterBase;
+use kernel::io::register::RegisterBase;

/// Type specifying the `Sec2` falcon engine. Cannot be instantiated.
pub(crate) struct Sec2(());
diff --git a/drivers/gpu/nova-core/nova_core.rs b/drivers/gpu/nova-core/nova_core.rs
index 112277c7921e..fffcaee2249f 100644
--- a/drivers/gpu/nova-core/nova_core.rs
+++ b/drivers/gpu/nova-core/nova_core.rs
@@ -2,9 +2,6 @@

//! Nova Core GPU Driver

-#[macro_use]
-mod bitfield;
-
mod dma;
mod driver;
mod falcon;
diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
index 206dab2e1335..1f08e6d4045a 100644
--- a/drivers/gpu/nova-core/regs.rs
+++ b/drivers/gpu/nova-core/regs.rs
@@ -4,15 +4,13 @@
// but are mapped to types.
#![allow(non_camel_case_types)]

-#[macro_use]
-pub(crate) mod macros;
-
use crate::falcon::{
DmaTrfCmdSize, FalconCoreRev, FalconCoreRevSubversion, FalconFbifMemType, FalconFbifTarget,
FalconModSelAlgo, FalconSecurityModel, PFalcon2Base, PFalconBase, PeregrineCoreSelect,
};
use crate::gpu::{Architecture, Chipset};
use kernel::prelude::*;
+use kernel::register;

// PMC

@@ -331,6 +329,7 @@ pub(crate) fn mem_scrubbing_done(self) -> bool {

pub(crate) mod gm107 {
// FUSE
+ use kernel::register;

register!(NV_FUSE_STATUS_OPT_DISPLAY @ 0x00021c04 {
0:0 display_disabled as bool;
@@ -339,6 +338,7 @@ pub(crate) mod gm107 {

pub(crate) mod ga100 {
// FUSE
+ use kernel::register;

register!(NV_FUSE_STATUS_OPT_DISPLAY @ 0x00820c04 {
0:0 display_disabled as bool;
diff --git a/rust/kernel/bits.rs b/rust/kernel/bits.rs
index 553d50265883..590a77d99ad7 100644
--- a/rust/kernel/bits.rs
+++ b/rust/kernel/bits.rs
@@ -201,3 +201,5 @@ pub const fn [<genmask_ $ty>](range: RangeInclusive<u32>) -> $ty {
/// assert_eq!(genmask_u8(0..=7), u8::MAX);
/// ```
);
+
+pub mod bitfield;
diff --git a/drivers/gpu/nova-core/bitfield.rs b/rust/kernel/bits/bitfield.rs
similarity index 91%
rename from drivers/gpu/nova-core/bitfield.rs
rename to rust/kernel/bits/bitfield.rs
index 9c022fc2bd6a..6089f3cdbd1b 100644
--- a/drivers/gpu/nova-core/bitfield.rs
+++ b/rust/kernel/bits/bitfield.rs
@@ -80,10 +80,13 @@
//! - `as <type> ?=> <try_into_type>` calls `<try_into_type>`'s `TryFrom::<<type>>` implementation
//! and returns the result. This is useful with fields for which not all values are valid.
//!
+
+/// bitfield macro definition
+#[macro_export]
macro_rules! bitfield {
// Main entry point - defines the bitfield struct with fields
($vis:vis struct $name:ident : $storage:ty $(, $comment:literal)? { $($fields:tt)* }) => {
- bitfield!(@core $vis $name $storage $(, $comment)? { $($fields)* });
+ ::kernel::bitfield!(@core $vis $name $storage $(, $comment)? { $($fields)* });
};

// All rules below are helpers.
@@ -118,7 +121,7 @@ fn from(val: $storage) -> Self {
}
}

- bitfield!(@fields_dispatcher $vis $name $storage { $($fields)* });
+ ::kernel::bitfield!(@fields_dispatcher $vis $name $storage { $($fields)* });
};

// Captures the fields and passes them to all the implementers that require field information.
@@ -134,7 +137,7 @@ fn from(val: $storage) -> Self {
)*
}
) => {
- bitfield!(@field_accessors $vis $name $storage {
+ ::kernel::bitfield!(@field_accessors $vis $name $storage {
$(
$hi:$lo $field as $type
$(?=> $try_into_type)?
@@ -143,8 +146,8 @@ fn from(val: $storage) -> Self {
;
)*
});
- bitfield!(@debug $name { $($field;)* });
- bitfield!(@default $name { $($field;)* });
+ ::kernel::bitfield!(@debug $name { $($field;)* });
+ ::kernel::bitfield!(@default $name { $($field;)* });
};

// Defines all the field getter/setter methods for `$name`.
@@ -159,7 +162,7 @@ fn from(val: $storage) -> Self {
}
) => {
$(
- bitfield!(@check_field_bounds $hi:$lo $field as $type);
+ ::kernel::bitfield!(@check_field_bounds $hi:$lo $field as $type);
)*

#[allow(dead_code)]
@@ -171,7 +174,7 @@ impl $name {
}

$(
- bitfield!(@field_accessor $vis $name $storage, $hi:$lo $field as $type
+ ::kernel::bitfield!(@field_accessor $vis $name $storage, $hi:$lo $field as $type
$(?=> $try_into_type)?
$(=> $into_type)?
$(, $comment)?
@@ -208,7 +211,7 @@ impl $name {
@field_accessor $vis:vis $name:ident $storage:ty, $hi:tt:$lo:tt $field:ident as bool => $into_type:ty
$(, $comment:literal)?;
) => {
- bitfield!(
+ ::kernel::bitfield!(
@leaf_accessor $vis $name $storage, $hi:$lo $field
{ |f| <$into_type>::from(if f != 0 { true } else { false }) }
$into_type => $into_type $(, $comment)?;
@@ -219,7 +222,7 @@ impl $name {
(
@field_accessor $vis:vis $name:ident $storage:ty, $hi:tt:$lo:tt $field:ident as bool $(, $comment:literal)?;
) => {
- bitfield!(@field_accessor $vis $name $storage, $hi:$lo $field as bool => bool $(, $comment)?;);
+ ::kernel::bitfield!(@field_accessor $vis $name $storage, $hi:$lo $field as bool => bool $(, $comment)?;);
};

// Catches the `?=>` syntax for non-boolean fields.
@@ -227,7 +230,7 @@ impl $name {
@field_accessor $vis:vis $name:ident $storage:ty, $hi:tt:$lo:tt $field:ident as $type:tt ?=> $try_into_type:ty
$(, $comment:literal)?;
) => {
- bitfield!(@leaf_accessor $vis $name $storage, $hi:$lo $field
+ ::kernel::bitfield!(@leaf_accessor $vis $name $storage, $hi:$lo $field
{ |f| <$try_into_type>::try_from(f as $type) } $try_into_type =>
::core::result::Result<
$try_into_type,
@@ -241,7 +244,7 @@ impl $name {
@field_accessor $vis:vis $name:ident $storage:ty, $hi:tt:$lo:tt $field:ident as $type:tt => $into_type:ty
$(, $comment:literal)?;
) => {
- bitfield!(@leaf_accessor $vis $name $storage, $hi:$lo $field
+ ::kernel::bitfield!(@leaf_accessor $vis $name $storage, $hi:$lo $field
{ |f| <$into_type>::from(f as $type) } $into_type => $into_type $(, $comment)?;);
};

@@ -250,7 +253,7 @@ impl $name {
@field_accessor $vis:vis $name:ident $storage:ty, $hi:tt:$lo:tt $field:ident as $type:tt
$(, $comment:literal)?;
) => {
- bitfield!(@field_accessor $vis $name $storage, $hi:$lo $field as $type => $type $(, $comment)?;);
+ ::kernel::bitfield!(@field_accessor $vis $name $storage, $hi:$lo $field as $type => $type $(, $comment)?;);
};

// Generates the accessor methods for a single field.
diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
index ee182b0b5452..da1384fd9ab6 100644
--- a/rust/kernel/io.rs
+++ b/rust/kernel/io.rs
@@ -9,6 +9,7 @@

pub mod mem;
pub mod poll;
+pub mod register;
pub mod resource;

pub use resource::Resource;
diff --git a/drivers/gpu/nova-core/regs/macros.rs b/rust/kernel/io/register.rs
similarity index 93%
rename from drivers/gpu/nova-core/regs/macros.rs
rename to rust/kernel/io/register.rs
index 6a4f3271beb3..088a8590db92 100644
--- a/drivers/gpu/nova-core/regs/macros.rs
+++ b/rust/kernel/io/register.rs
@@ -17,7 +17,8 @@
/// The `T` generic argument is used to distinguish which base to use, in case a type provides
/// several bases. It is given to the `register!` macro to restrict the use of the register to
/// implementors of this particular variant.
-pub(crate) trait RegisterBase<T> {
+pub trait RegisterBase<T> {
+ /// The base address for the register.
const BASE: usize;
}

@@ -273,28 +274,29 @@ pub(crate) trait RegisterBase<T> {
/// # Ok(())
/// # }
/// ```
+#[macro_export]
macro_rules! register {
// Creates a register at a fixed offset of the MMIO space.
($name:ident @ $offset:literal $(, $comment:literal)? { $($fields:tt)* } ) => {
- bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
+ ::kernel::bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
register!(@io_fixed $name @ $offset);
};

// Creates an alias register of fixed offset register `alias` with its own fields.
($name:ident => $alias:ident $(, $comment:literal)? { $($fields:tt)* } ) => {
- bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
+ ::kernel::bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
register!(@io_fixed $name @ $alias::OFFSET);
};

// Creates a register at a relative offset from a base address provider.
($name:ident @ $base:ty [ $offset:literal ] $(, $comment:literal)? { $($fields:tt)* } ) => {
- bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
+ ::kernel::bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
register!(@io_relative $name @ $base [ $offset ]);
};

// Creates an alias register of relative offset register `alias` with its own fields.
($name:ident => $base:ty [ $alias:ident ] $(, $comment:literal)? { $($fields:tt)* }) => {
- bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
+ ::kernel::bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
register!(@io_relative $name @ $base [ $alias::OFFSET ]);
};

@@ -305,7 +307,7 @@ macro_rules! register {
}
) => {
static_assert!(::core::mem::size_of::<u32>() <= $stride);
- bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
+ ::kernel::bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
register!(@io_array $name @ $offset [ $size ; $stride ]);
};

@@ -326,7 +328,7 @@ macro_rules! register {
$(, $comment:literal)? { $($fields:tt)* }
) => {
static_assert!(::core::mem::size_of::<u32>() <= $stride);
- bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
+ ::kernel::bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
register!(@io_relative_array $name @ $base [ $offset [ $size ; $stride ] ]);
};

@@ -348,7 +350,7 @@ macro_rules! register {
}
) => {
static_assert!($idx < $alias::SIZE);
- bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
+ ::kernel::bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
register!(@io_relative $name @ $base [ $alias::OFFSET + $idx * $alias::STRIDE ] );
};

@@ -357,7 +359,7 @@ macro_rules! register {
// to avoid it being interpreted in place of the relative register array alias rule.
($name:ident => $alias:ident [ $idx:expr ] $(, $comment:literal)? { $($fields:tt)* }) => {
static_assert!($idx < $alias::SIZE);
- bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
+ ::kernel::bitfield!(pub(crate) struct $name: u32 $(, $comment)? { $($fields)* } );
register!(@io_fixed $name @ $alias::OFFSET + $idx * $alias::STRIDE );
};

@@ -414,12 +416,12 @@ pub(crate) fn read<const SIZE: usize, T, B>(
base: &B,
) -> Self where
T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
- B: crate::regs::macros::RegisterBase<$base>,
+ B: ::kernel::io::register::RegisterBase<$base>,
{
const OFFSET: usize = $name::OFFSET;

let value = io.read32(
- <B as crate::regs::macros::RegisterBase<$base>>::BASE + OFFSET
+ <B as ::kernel::io::register::RegisterBase<$base>>::BASE + OFFSET
);

Self(value)
@@ -435,13 +437,13 @@ pub(crate) fn write<const SIZE: usize, T, B>(
base: &B,
) where
T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
- B: crate::regs::macros::RegisterBase<$base>,
+ B: ::kernel::io::register::RegisterBase<$base>,
{
const OFFSET: usize = $name::OFFSET;

io.write32(
self.0,
- <B as crate::regs::macros::RegisterBase<$base>>::BASE + OFFSET
+ <B as ::kernel::io::register::RegisterBase<$base>>::BASE + OFFSET
);
}

@@ -455,7 +457,7 @@ pub(crate) fn alter<const SIZE: usize, T, B, F>(
f: F,
) where
T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
- B: crate::regs::macros::RegisterBase<$base>,
+ B: ::kernel::io::register::RegisterBase<$base>,
F: ::core::ops::FnOnce(Self) -> Self,
{
let reg = f(Self::read(io, base));
@@ -600,11 +602,11 @@ pub(crate) fn read<const SIZE: usize, T, B>(
idx: usize,
) -> Self where
T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
- B: crate::regs::macros::RegisterBase<$base>,
+ B: ::kernel::io::register::RegisterBase<$base>,
{
build_assert!(idx < Self::SIZE);

- let offset = <B as crate::regs::macros::RegisterBase<$base>>::BASE +
+ let offset = <B as ::kernel::io::register::RegisterBase<$base>>::BASE +
Self::OFFSET + (idx * Self::STRIDE);
let value = io.read32(offset);

@@ -622,11 +624,11 @@ pub(crate) fn write<const SIZE: usize, T, B>(
idx: usize
) where
T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
- B: crate::regs::macros::RegisterBase<$base>,
+ B: ::kernel::io::register::RegisterBase<$base>,
{
build_assert!(idx < Self::SIZE);

- let offset = <B as crate::regs::macros::RegisterBase<$base>>::BASE +
+ let offset = <B as ::kernel::io::register::RegisterBase<$base>>::BASE +
Self::OFFSET + (idx * Self::STRIDE);

io.write32(self.0, offset);
@@ -643,7 +645,7 @@ pub(crate) fn alter<const SIZE: usize, T, B, F>(
f: F,
) where
T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
- B: crate::regs::macros::RegisterBase<$base>,
+ B: ::kernel::io::register::RegisterBase<$base>,
F: ::core::ops::FnOnce(Self) -> Self,
{
let reg = f(Self::read(io, base, idx));
@@ -662,7 +664,7 @@ pub(crate) fn try_read<const SIZE: usize, T, B>(
idx: usize,
) -> ::kernel::error::Result<Self> where
T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
- B: crate::regs::macros::RegisterBase<$base>,
+ B: ::kernel::io::register::RegisterBase<$base>,
{
if idx < Self::SIZE {
Ok(Self::read(io, base, idx))
@@ -684,7 +686,7 @@ pub(crate) fn try_write<const SIZE: usize, T, B>(
idx: usize,
) -> ::kernel::error::Result where
T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
- B: crate::regs::macros::RegisterBase<$base>,
+ B: ::kernel::io::register::RegisterBase<$base>,
{
if idx < Self::SIZE {
Ok(self.write(io, base, idx))
@@ -707,7 +709,7 @@ pub(crate) fn try_alter<const SIZE: usize, T, B, F>(
f: F,
) -> ::kernel::error::Result where
T: ::core::ops::Deref<Target = ::kernel::io::Io<SIZE>>,
- B: crate::regs::macros::RegisterBase<$base>,
+ B: ::kernel::io::register::RegisterBase<$base>,
F: ::core::ops::FnOnce(Self) -> Self,
{
if idx < Self::SIZE {
--
2.34.1