[PATCH v5 0/3] rust, nova-core: add SizeConstants trait for SZ_* constants

[PATCH v5 0/3] rust, nova-core: add SizeConstants trait for SZ_* constants

[John Hubbard]

Changes in v5:
  * Changed the subject line of this cover letter to not use the old
    DeviceSize name.

  * Collected Reviewed-by tags from Alexandre Courbot and Joel
    Fernandes, and Acked-by from Gary Guo.

  * Added a new patch 3/3 with a todo.rst entry for device address
    type wrappers and a marker trait, as discussed with Danilo.

  * Rebased onto latest drm-rust-next.

Changes in v4:
  * Renamed the trait from DeviceSize to SizeConstants.

  * Added backticks and trailing periods to all hex-value doc comments
    on the SZ_* constants.

  * Removed redundant type annotations from doc-test examples.

  * Used a `use` import for PAGE_SIZE in the module-level doc-test
    instead of a fully qualified path.

  * Rewrote doc-test comments to clarify the distinction between
    module-level constants (no type qualifier) and trait associated
    constants (type qualifier required).

  * Added Reviewed-by from Eliot Courtney.

Changes in v3:
  * Dropped the Alignment::from_u64() patch.

  * Reworked define_sizes! macro to accept target types as arguments
    (define_sizes!(u32, u64, usize)) using recursive macro arms,
    instead of hardcoding impls for u32 and u64. Overflow checking
    uses u128 casts so the same assert works for any ("reasonable")
    target type.

  * Added usize to the DeviceSize implementations, so the trait
    covers u32, u64, and usize.

  * Hex values for each constant are now proper doc-comments
    (forwarded via macro meta), instead of inline comments.

  * Rebased onto latest drm-rust-next.

Changes in v2:
  * Replaced flat SZ_*_U64 constants with a DeviceSize trait that
    provides SZ_* as associated constants on u32 and u64.

  * A define_sizes! macro generates everything from one list of names.

  * Added Alignment::from_u64() so alignment values can be constructed
    from DeviceSize constants without falling back to usize variants.

  * Rebased onto drm-rust-next. No longer depends on the Blackwell
    patchset.

v1 is here:
    https://lore.kernel.org/20260310023145.120037-1-jhubbard@nvidia.com

John Hubbard (3):
  rust: sizes: add SizeConstants trait for device address space
    constants
  gpu: nova-core: use SizeConstants trait for u64 size constants
  gpu: nova-core: add task for device address type wrappers

 Documentation/gpu/nova/core/todo.rst |  13 +++
 drivers/gpu/nova-core/fb.rs          |  21 ++--
 drivers/gpu/nova-core/gsp/fw.rs      |  15 ++-
 drivers/gpu/nova-core/regs.rs        |   7 +-
 rust/kernel/sizes.rs                 | 167 ++++++++++++++++++++-------
 5 files changed, 155 insertions(+), 68 deletions(-)


base-commit: 7c50d748b4a635bc39802ea3f6b120e66b1b9067
-- 
2.53.0

[PATCH v5 1/3] rust: sizes: add SizeConstants trait for device address space constants

[John Hubbard]

The SZ_* constants are usize, matching the CPU pointer width. But
device address spaces have their own widths (32-bit MMIO windows,
64-bit GPU framebuffers, etc.), so drivers end up casting these
constants with SZ_1M as u64 or helper functions. This adds
boilerplate with no safety benefit.

Add a SizeConstants trait with associated SZ_* constants, implemented
for u32, u64, and usize. With the trait in scope, callers write
u64::SZ_1M or u32::SZ_4K to get the constant in their device's
native width. All SZ_* values fit in a u32, so every implementation
is lossless. Each impl has a const assert to catch any future
constant that would overflow.

A define_sizes! macro generates everything from a single internal
list of names. The macro takes the target types as arguments, so
adding a new target type requires changing only the call site.

Suggested-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/all/DGB9G697GSWO.3VBFGU5MKFPMR@kernel.org/
Link: https://lore.kernel.org/all/DGHI8WRKBQS9.38910L6FIIZTE@kernel.org/
Reviewed-by: Eliot Courtney <ecourtney@nvidia.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Gary Guo <gary@garyguo.net>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 rust/kernel/sizes.rs | 167 +++++++++++++++++++++++++++++++------------
 1 file changed, 123 insertions(+), 44 deletions(-)

diff --git a/rust/kernel/sizes.rs b/rust/kernel/sizes.rs
index 661e680d9330..837404a2042b 100644
--- a/rust/kernel/sizes.rs
+++ b/rust/kernel/sizes.rs
@@ -3,48 +3,127 @@
 //! Commonly used sizes.
 //!
 //! C headers: [`include/linux/sizes.h`](srctree/include/linux/sizes.h).
+//!
+//! The top-level `SZ_*` constants are [`usize`]-typed, for use in kernel page
+//! arithmetic and similar CPU-side work.
+//!
+//! The [`SizeConstants`] trait provides the same constants as associated constants
+//! on [`u32`], [`u64`], and [`usize`], for use in device address spaces where
+//! the address width depends on the hardware. Device drivers frequently need
+//! these constants as [`u64`] (or [`u32`]) rather than [`usize`], because
+//! device address spaces are sized independently of the CPU pointer width.
+//!
+//! # Examples
+//!
+//! ```
+//! use kernel::page::PAGE_SIZE;
+//! use kernel::sizes::{SizeConstants, SZ_1M};
+//!
+//! // Module-level constants continue to work without a type qualifier.
+//! let num_pages_in_1m = SZ_1M / PAGE_SIZE;
+//!
+//! // Trait associated constants require a type qualifier.
+//! let heap_size = 14 * u64::SZ_1M;
+//! let small = u32::SZ_4K;
+//! ```
+
+macro_rules! define_sizes {
+    ($($type:ty),* $(,)?) => {
+        define_sizes!(@internal [$($type),*]
+            /// `0x0000_0400`.
+            SZ_1K,
+            /// `0x0000_0800`.
+            SZ_2K,
+            /// `0x0000_1000`.
+            SZ_4K,
+            /// `0x0000_2000`.
+            SZ_8K,
+            /// `0x0000_4000`.
+            SZ_16K,
+            /// `0x0000_8000`.
+            SZ_32K,
+            /// `0x0001_0000`.
+            SZ_64K,
+            /// `0x0002_0000`.
+            SZ_128K,
+            /// `0x0004_0000`.
+            SZ_256K,
+            /// `0x0008_0000`.
+            SZ_512K,
+            /// `0x0010_0000`.
+            SZ_1M,
+            /// `0x0020_0000`.
+            SZ_2M,
+            /// `0x0040_0000`.
+            SZ_4M,
+            /// `0x0080_0000`.
+            SZ_8M,
+            /// `0x0100_0000`.
+            SZ_16M,
+            /// `0x0200_0000`.
+            SZ_32M,
+            /// `0x0400_0000`.
+            SZ_64M,
+            /// `0x0800_0000`.
+            SZ_128M,
+            /// `0x1000_0000`.
+            SZ_256M,
+            /// `0x2000_0000`.
+            SZ_512M,
+            /// `0x4000_0000`.
+            SZ_1G,
+            /// `0x8000_0000`.
+            SZ_2G,
+        );
+    };
+
+    (@internal [$($type:ty),*] $($names_and_metas:tt)*) => {
+        define_sizes!(@consts_and_trait $($names_and_metas)*);
+        define_sizes!(@impls [$($type),*] $($names_and_metas)*);
+    };
+
+    (@consts_and_trait $($(#[$meta:meta])* $name:ident,)*) => {
+        $(
+            $(#[$meta])*
+            pub const $name: usize = bindings::$name as usize;
+        )*
+
+        /// Size constants for device address spaces.
+        ///
+        /// Implemented for [`u32`], [`u64`], and [`usize`] so drivers can
+        /// choose the width that matches their hardware. All `SZ_*` values fit
+        /// in a [`u32`], so all implementations are lossless.
+        ///
+        /// # Examples
+        ///
+        /// ```
+        /// use kernel::sizes::SizeConstants;
+        ///
+        /// let gpu_heap = 14 * u64::SZ_1M;
+        /// let mmio_window = u32::SZ_16M;
+        /// ```
+        pub trait SizeConstants {
+            $(
+                $(#[$meta])*
+                const $name: Self;
+            )*
+        }
+    };
+
+    (@impls [] $($(#[$meta:meta])* $name:ident,)*) => {};
+
+    (@impls [$first:ty $(, $rest:ty)*] $($(#[$meta:meta])* $name:ident,)*) => {
+        impl SizeConstants for $first {
+            $(
+                const $name: Self = {
+                    assert!((self::$name as u128) <= (<$first>::MAX as u128));
+                    self::$name as $first
+                };
+            )*
+        }
+
+        define_sizes!(@impls [$($rest),*] $($(#[$meta])* $name,)*);
+    };
+}
 
-/// 0x00000400
-pub const SZ_1K: usize = bindings::SZ_1K as usize;
-/// 0x00000800
-pub const SZ_2K: usize = bindings::SZ_2K as usize;
-/// 0x00001000
-pub const SZ_4K: usize = bindings::SZ_4K as usize;
-/// 0x00002000
-pub const SZ_8K: usize = bindings::SZ_8K as usize;
-/// 0x00004000
-pub const SZ_16K: usize = bindings::SZ_16K as usize;
-/// 0x00008000
-pub const SZ_32K: usize = bindings::SZ_32K as usize;
-/// 0x00010000
-pub const SZ_64K: usize = bindings::SZ_64K as usize;
-/// 0x00020000
-pub const SZ_128K: usize = bindings::SZ_128K as usize;
-/// 0x00040000
-pub const SZ_256K: usize = bindings::SZ_256K as usize;
-/// 0x00080000
-pub const SZ_512K: usize = bindings::SZ_512K as usize;
-/// 0x00100000
-pub const SZ_1M: usize = bindings::SZ_1M as usize;
-/// 0x00200000
-pub const SZ_2M: usize = bindings::SZ_2M as usize;
-/// 0x00400000
-pub const SZ_4M: usize = bindings::SZ_4M as usize;
-/// 0x00800000
-pub const SZ_8M: usize = bindings::SZ_8M as usize;
-/// 0x01000000
-pub const SZ_16M: usize = bindings::SZ_16M as usize;
-/// 0x02000000
-pub const SZ_32M: usize = bindings::SZ_32M as usize;
-/// 0x04000000
-pub const SZ_64M: usize = bindings::SZ_64M as usize;
-/// 0x08000000
-pub const SZ_128M: usize = bindings::SZ_128M as usize;
-/// 0x10000000
-pub const SZ_256M: usize = bindings::SZ_256M as usize;
-/// 0x20000000
-pub const SZ_512M: usize = bindings::SZ_512M as usize;
-/// 0x40000000
-pub const SZ_1G: usize = bindings::SZ_1G as usize;
-/// 0x80000000
-pub const SZ_2G: usize = bindings::SZ_2G as usize;
+define_sizes!(u32, u64, usize);
-- 
2.53.0

Re: [PATCH v5 1/3] rust: sizes: add SizeConstants trait for device address space constants

[Miguel Ojeda]

On Sat, Apr 4, 2026 at 4:12 AM John Hubbard <jhubbard@nvidia.com> wrote:
>
> The SZ_* constants are usize, matching the CPU pointer width. But
> device address spaces have their own widths (32-bit MMIO windows,
> 64-bit GPU framebuffers, etc.), so drivers end up casting these
> constants with SZ_1M as u64 or helper functions. This adds
> boilerplate with no safety benefit.
>
> Add a SizeConstants trait with associated SZ_* constants, implemented
> for u32, u64, and usize. With the trait in scope, callers write
> u64::SZ_1M or u32::SZ_4K to get the constant in their device's
> native width. All SZ_* values fit in a u32, so every implementation
> is lossless. Each impl has a const assert to catch any future
> constant that would overflow.
>
> A define_sizes! macro generates everything from a single internal
> list of names. The macro takes the target types as arguments, so
> adding a new target type requires changing only the call site.
>
> Suggested-by: Danilo Krummrich <dakr@kernel.org>
> Link: https://lore.kernel.org/all/DGB9G697GSWO.3VBFGU5MKFPMR@kernel.org/
> Link: https://lore.kernel.org/all/DGHI8WRKBQS9.38910L6FIIZTE@kernel.org/
> Reviewed-by: Eliot Courtney <ecourtney@nvidia.com>
> Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
> Acked-by: Gary Guo <gary@garyguo.net>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>

If there are no concerns, then I will pick this one up.

Thanks!

Cheers,
Miguel

Re: [PATCH v5 1/3] rust: sizes: add SizeConstants trait for device address space constants

[Alexandre Courbot]

On Sat Apr 4, 2026 at 11:33 AM JST, Miguel Ojeda wrote:
> On Sat, Apr 4, 2026 at 4:12 AM John Hubbard <jhubbard@nvidia.com> wrote:
>>
>> The SZ_* constants are usize, matching the CPU pointer width. But
>> device address spaces have their own widths (32-bit MMIO windows,
>> 64-bit GPU framebuffers, etc.), so drivers end up casting these
>> constants with SZ_1M as u64 or helper functions. This adds
>> boilerplate with no safety benefit.
>>
>> Add a SizeConstants trait with associated SZ_* constants, implemented
>> for u32, u64, and usize. With the trait in scope, callers write
>> u64::SZ_1M or u32::SZ_4K to get the constant in their device's
>> native width. All SZ_* values fit in a u32, so every implementation
>> is lossless. Each impl has a const assert to catch any future
>> constant that would overflow.
>>
>> A define_sizes! macro generates everything from a single internal
>> list of names. The macro takes the target types as arguments, so
>> adding a new target type requires changing only the call site.
>>
>> Suggested-by: Danilo Krummrich <dakr@kernel.org>
>> Link: https://lore.kernel.org/all/DGB9G697GSWO.3VBFGU5MKFPMR@kernel.org/
>> Link: https://lore.kernel.org/all/DGHI8WRKBQS9.38910L6FIIZTE@kernel.org/
>> Reviewed-by: Eliot Courtney <ecourtney@nvidia.com>
>> Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
>> Acked-by: Gary Guo <gary@garyguo.net>
>> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
>
> If there are no concerns, then I will pick this one up.

No concern from me, the user code in Nova will be scheduled for the 7.2
merge window anyway.

[PATCH v5 2/3] gpu: nova-core: use SizeConstants trait for u64 size constants

[John Hubbard]

Replace manual usize-to-u64 conversions of SZ_* constants with the
SizeConstants trait's associated constants on u64. With the
SizeConstants trait in scope, u64::SZ_1M replaces usize_as_u64(SZ_1M)
and similar.

This removes several now-unused imports: usize_as_u64, FromSafeCast,
and individual SZ_* type-level constants.

Reviewed-by: Eliot Courtney <ecourtney@nvidia.com>
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Acked-by: Gary Guo <gary@garyguo.net>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/fb.rs     | 21 +++++++++------------
 drivers/gpu/nova-core/gsp/fw.rs | 15 +++++++--------
 drivers/gpu/nova-core/regs.rs   |  7 +++----
 3 files changed, 19 insertions(+), 24 deletions(-)

diff --git a/drivers/gpu/nova-core/fb.rs b/drivers/gpu/nova-core/fb.rs
index bdd5eed760e1..5c304fc03467 100644
--- a/drivers/gpu/nova-core/fb.rs
+++ b/drivers/gpu/nova-core/fb.rs
@@ -24,11 +24,8 @@
     firmware::gsp::GspFirmware,
     gpu::Chipset,
     gsp,
-    num::{
-        usize_as_u64,
-        FromSafeCast, //
-    },
-    regs,
+    num::FromSafeCast,
+    regs, //
 };
 
 mod hal;
@@ -127,8 +124,8 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         if f.alternate() {
             let size = self.len();
 
-            if size < usize_as_u64(SZ_1M) {
-                let size_kib = size / usize_as_u64(SZ_1K);
+            if size < u64::SZ_1M {
+                let size_kib = size / u64::SZ_1K;
                 f.write_fmt(fmt!(
                     "{:#x}..{:#x} ({} KiB)",
                     self.0.start,
@@ -136,7 +133,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                     size_kib
                 ))
             } else {
-                let size_mib = size / usize_as_u64(SZ_1M);
+                let size_mib = size / u64::SZ_1M;
                 f.write_fmt(fmt!(
                     "{:#x}..{:#x} ({} MiB)",
                     self.0.start,
@@ -186,7 +183,7 @@ pub(crate) fn new(chipset: Chipset, bar: &Bar0, gsp_fw: &GspFirmware) -> Result<
 
         let vga_workspace = {
             let vga_base = {
-                const NV_PRAMIN_SIZE: u64 = usize_as_u64(SZ_1M);
+                const NV_PRAMIN_SIZE: u64 = u64::SZ_1M;
                 let base = fb.end - NV_PRAMIN_SIZE;
 
                 if hal.supports_display(bar) {
@@ -196,7 +193,7 @@ pub(crate) fn new(chipset: Chipset, bar: &Bar0, gsp_fw: &GspFirmware) -> Result<
                     {
                         Some(addr) => {
                             if addr < base {
-                                const VBIOS_WORKSPACE_SIZE: u64 = usize_as_u64(SZ_128K);
+                                const VBIOS_WORKSPACE_SIZE: u64 = u64::SZ_128K;
 
                                 // Point workspace address to end of framebuffer.
                                 fb.end - VBIOS_WORKSPACE_SIZE
@@ -216,7 +213,7 @@ pub(crate) fn new(chipset: Chipset, bar: &Bar0, gsp_fw: &GspFirmware) -> Result<
 
         let frts = {
             const FRTS_DOWN_ALIGN: Alignment = Alignment::new::<SZ_128K>();
-            const FRTS_SIZE: u64 = usize_as_u64(SZ_1M);
+            const FRTS_SIZE: u64 = u64::SZ_1M;
             let frts_base = vga_workspace.start.align_down(FRTS_DOWN_ALIGN) - FRTS_SIZE;
 
             FbRange(frts_base..frts_base + FRTS_SIZE)
@@ -256,7 +253,7 @@ pub(crate) fn new(chipset: Chipset, bar: &Bar0, gsp_fw: &GspFirmware) -> Result<
         };
 
         let heap = {
-            const HEAP_SIZE: u64 = usize_as_u64(SZ_1M);
+            const HEAP_SIZE: u64 = u64::SZ_1M;
 
             FbRange(wpr2.start - HEAP_SIZE..wpr2.start)
         };
diff --git a/drivers/gpu/nova-core/gsp/fw.rs b/drivers/gpu/nova-core/gsp/fw.rs
index 0c8a74f0e8ac..9dac3288f3a3 100644
--- a/drivers/gpu/nova-core/gsp/fw.rs
+++ b/drivers/gpu/nova-core/gsp/fw.rs
@@ -17,8 +17,8 @@
         KnownSize, //
     },
     sizes::{
-        SZ_128K,
-        SZ_1M, //
+        SizeConstants,
+        SZ_128K, //
     },
     transmute::{
         AsBytes,
@@ -123,7 +123,7 @@ fn client_alloc_size() -> u64 {
     /// Returns the amount of memory to reserve for management purposes for a framebuffer of size
     /// `fb_size`.
     fn management_overhead(fb_size: u64) -> u64 {
-        let fb_size_gb = fb_size.div_ceil(u64::from_safe_cast(kernel::sizes::SZ_1G));
+        let fb_size_gb = fb_size.div_ceil(u64::SZ_1G);
 
         u64::from(bindings::GSP_FW_HEAP_PARAM_SIZE_PER_GB_FB)
             .saturating_mul(fb_size_gb)
@@ -145,9 +145,8 @@ impl LibosParams {
     const LIBOS2: LibosParams = LibosParams {
         carveout_size: num::u32_as_u64(bindings::GSP_FW_HEAP_PARAM_OS_SIZE_LIBOS2),
         allowed_heap_size: num::u32_as_u64(bindings::GSP_FW_HEAP_SIZE_OVERRIDE_LIBOS2_MIN_MB)
-            * num::usize_as_u64(SZ_1M)
-            ..num::u32_as_u64(bindings::GSP_FW_HEAP_SIZE_OVERRIDE_LIBOS2_MAX_MB)
-                * num::usize_as_u64(SZ_1M),
+            * u64::SZ_1M
+            ..num::u32_as_u64(bindings::GSP_FW_HEAP_SIZE_OVERRIDE_LIBOS2_MAX_MB) * u64::SZ_1M,
     };
 
     /// Version 3 of the GSP LIBOS (GA102+)
@@ -155,9 +154,9 @@ impl LibosParams {
         carveout_size: num::u32_as_u64(bindings::GSP_FW_HEAP_PARAM_OS_SIZE_LIBOS3_BAREMETAL),
         allowed_heap_size: num::u32_as_u64(
             bindings::GSP_FW_HEAP_SIZE_OVERRIDE_LIBOS3_BAREMETAL_MIN_MB,
-        ) * num::usize_as_u64(SZ_1M)
+        ) * u64::SZ_1M
             ..num::u32_as_u64(bindings::GSP_FW_HEAP_SIZE_OVERRIDE_LIBOS3_BAREMETAL_MAX_MB)
-                * num::usize_as_u64(SZ_1M),
+                * u64::SZ_1M,
     };
 
     /// Returns the libos parameters corresponding to `chipset`.
diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
index 2f171a4ff9ba..6faeed73901d 100644
--- a/drivers/gpu/nova-core/regs.rs
+++ b/drivers/gpu/nova-core/regs.rs
@@ -7,6 +7,7 @@
         Io, //
     },
     prelude::*,
+    sizes::SizeConstants,
     time, //
 };
 
@@ -30,7 +31,6 @@
         Architecture,
         Chipset, //
     },
-    num::FromSafeCast,
 };
 
 // PMC
@@ -150,8 +150,7 @@ fn fmt(&self, f: &mut kernel::fmt::Formatter<'_>) -> kernel::fmt::Result {
 impl NV_PFB_PRI_MMU_LOCAL_MEMORY_RANGE {
     /// Returns the usable framebuffer size, in bytes.
     pub(crate) fn usable_fb_size(self) -> u64 {
-        let size = (u64::from(self.lower_mag()) << u64::from(self.lower_scale()))
-            * u64::from_safe_cast(kernel::sizes::SZ_1M);
+        let size = (u64::from(self.lower_mag()) << u64::from(self.lower_scale())) * u64::SZ_1M;
 
         if self.ecc_mode_enabled() {
             // Remove the amount of memory reserved for ECC (one per 16 units).
@@ -241,7 +240,7 @@ pub(crate) fn completed(self) -> bool {
 impl NV_USABLE_FB_SIZE_IN_MB {
     /// Returns the usable framebuffer size, in bytes.
     pub(crate) fn usable_fb_size(self) -> u64 {
-        u64::from(self.value()) * u64::from_safe_cast(kernel::sizes::SZ_1M)
+        u64::from(self.value()) * u64::SZ_1M
     }
 }
 
-- 
2.53.0

[PATCH v5 3/3] gpu: nova-core: add task for device address type wrappers

[John Hubbard]

Add a todo.rst entry for creating newtype wrappers around integer types
for device addresses and sizes, with a marker trait that generic DRM
APIs can use as a bound.

Suggested-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 Documentation/gpu/nova/core/todo.rst | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/Documentation/gpu/nova/core/todo.rst b/Documentation/gpu/nova/core/todo.rst
index d5130b2b08fb..c06f274ed1b4 100644
--- a/Documentation/gpu/nova/core/todo.rst
+++ b/Documentation/gpu/nova/core/todo.rst
@@ -88,6 +88,19 @@ SR-IOV [1] is work in progress.
 | Complexity: Beginner
 | Link: https://lore.kernel.org/all/20251119-rust-pci-sriov-v1-0-883a94599a97@redhat.com/ [1]
 
+Device address type wrappers
+----------------------------
+
+The ``SizeConstants`` trait provides ``SZ_*`` constants as associated constants
+on ``u32``, ``u64``, and ``usize``. Device-centric APIs such as GPU VM
+management and buddy allocators could benefit from newtype wrappers around these
+integer types to represent device addresses and sizes. A separate marker trait
+could then serve as a generic bound for those wrappers.
+
+| Complexity: Intermediate
+| Link: https://lore.kernel.org/all/DHJJJNP5T5FZ.2HWBMOEEKH9ZR@kernel.org/
+| Contact: Danilo Krummrich
+
 GPU (general)
 =============
 
-- 
2.53.0