[PATCH 04/12] gpu: nova-core: mm: Add VramAddress type

[Eliot Courtney <ecourtney@nvidia.com>]

From: Joel Fernandes <joelagnelf@nvidia.com>

Add the `VramAddress` type representing a physical address in VRAM. Also
add an arithmetic helper, comparison, and operator overloads which are
required in later patches for address arithmetic.

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
[ecourtney: create mm.rs here, squashing in the arithmetic patch]
[ecourtney: splice the two commit bodies]
[ecourtney: drop the Pfn fields, open-coding what bitfield! generated]
[ecourtney: drop align_down and the IntoVramOffset/IntoVramRange traits]
[ecourtney: make checked_add() const over a plain u64, derive the ordering]
[ecourtney: doc wording, header, import, and signature cleanups]
Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 drivers/gpu/nova-core/mm.rs        | 60 ++++++++++++++++++++++++++++++++++++++
 drivers/gpu/nova-core/nova_core.rs |  1 +
 2 files changed, 61 insertions(+)

diff --git a/drivers/gpu/nova-core/mm.rs b/drivers/gpu/nova-core/mm.rs
new file mode 100644
index 000000000000..dcd5e5e919bf
--- /dev/null
+++ b/drivers/gpu/nova-core/mm.rs
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+
+//! Memory management subsystems.
+
+#![expect(dead_code)]
+
+use core::{
+    fmt::LowerHex,
+    ops, //
+};
+
+use kernel::fmt;
+
+/// Physical VRAM address in GPU video memory.
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+#[repr(transparent)]
+pub(crate) struct VramAddress(u64);
+
+impl VramAddress {
+    /// Creates an address from a raw value.
+    pub(crate) const fn from_raw(addr: u64) -> Self {
+        Self(addr)
+    }
+
+    /// Returns the address as a raw value.
+    pub(crate) const fn into_raw(self) -> u64 {
+        self.0
+    }
+
+    /// Adds `rhs` to this address, returning [`None`] on overflow.
+    pub(crate) const fn checked_add(self, rhs: u64) -> Option<Self> {
+        match self.into_raw().checked_add(rhs) {
+            Some(addr) => Some(Self::from_raw(addr)),
+            None => None,
+        }
+    }
+}
+
+impl LowerHex for VramAddress {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        LowerHex::fmt(&self.into_raw(), f)
+    }
+}
+
+impl ops::Add<u64> for VramAddress {
+    type Output = Self;
+
+    fn add(self, rhs: u64) -> Self::Output {
+        Self::from_raw(self.into_raw() + rhs)
+    }
+}
+
+impl ops::Sub for VramAddress {
+    type Output = u64;
+
+    fn sub(self, rhs: Self) -> Self::Output {
+        self.into_raw() - rhs.into_raw()
+    }
+}
diff --git a/drivers/gpu/nova-core/nova_core.rs b/drivers/gpu/nova-core/nova_core.rs
index 35a8b1214b0e..8f59cfa97017 100644
--- a/drivers/gpu/nova-core/nova_core.rs
+++ b/drivers/gpu/nova-core/nova_core.rs
@@ -18,6 +18,7 @@
 mod gpu;
 mod gsp;
 mod mctp;
+mod mm;
 #[macro_use]
 mod num;
 mod regs;

-- 
2.55.0