[PATCH v5 37/38] rust: sizes: add u64 variants of SZ_* constants

[John Hubbard]

Drivers that operate on 64-bit address spaces (GPU framebuffer layouts,
DMA regions, etc.) frequently need these size constants as a u64 type.
Today this requires repeated usize-to-u64 conversion calls like
usize_as_u64(SZ_1M) or u64::from_safe_cast(SZ_1M), which adds
boilerplate without any safety benefit.

Add u64-typed constants (SZ_1K_U64 through SZ_2G_U64) alongside the
existing usize constants. Every value fits in u64 (actually, within a
u32 for that matter), so the as-cast is always lossless.

Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
---
 rust/kernel/sizes.rs | 51 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/rust/kernel/sizes.rs b/rust/kernel/sizes.rs
index 661e680d9330..a11c134be64e 100644
--- a/rust/kernel/sizes.rs
+++ b/rust/kernel/sizes.rs
@@ -48,3 +48,54 @@
 pub const SZ_1G: usize = bindings::SZ_1G as usize;
 /// 0x80000000
 pub const SZ_2G: usize = bindings::SZ_2G as usize;
+
+// `u64` variants of the size constants. These are the same values as the
+// `usize` constants above, but typed as `u64` to avoid repeated conversion
+// boilerplate in code that operates on 64-bit address spaces.
+//
+// CAST: every SZ_* value below fits in u64, so `as u64` is always lossless.
+
+/// [`SZ_1K`] as a [`u64`].
+pub const SZ_1K_U64: u64 = SZ_1K as u64;
+/// [`SZ_2K`] as a [`u64`].
+pub const SZ_2K_U64: u64 = SZ_2K as u64;
+/// [`SZ_4K`] as a [`u64`].
+pub const SZ_4K_U64: u64 = SZ_4K as u64;
+/// [`SZ_8K`] as a [`u64`].
+pub const SZ_8K_U64: u64 = SZ_8K as u64;
+/// [`SZ_16K`] as a [`u64`].
+pub const SZ_16K_U64: u64 = SZ_16K as u64;
+/// [`SZ_32K`] as a [`u64`].
+pub const SZ_32K_U64: u64 = SZ_32K as u64;
+/// [`SZ_64K`] as a [`u64`].
+pub const SZ_64K_U64: u64 = SZ_64K as u64;
+/// [`SZ_128K`] as a [`u64`].
+pub const SZ_128K_U64: u64 = SZ_128K as u64;
+/// [`SZ_256K`] as a [`u64`].
+pub const SZ_256K_U64: u64 = SZ_256K as u64;
+/// [`SZ_512K`] as a [`u64`].
+pub const SZ_512K_U64: u64 = SZ_512K as u64;
+/// [`SZ_1M`] as a [`u64`].
+pub const SZ_1M_U64: u64 = SZ_1M as u64;
+/// [`SZ_2M`] as a [`u64`].
+pub const SZ_2M_U64: u64 = SZ_2M as u64;
+/// [`SZ_4M`] as a [`u64`].
+pub const SZ_4M_U64: u64 = SZ_4M as u64;
+/// [`SZ_8M`] as a [`u64`].
+pub const SZ_8M_U64: u64 = SZ_8M as u64;
+/// [`SZ_16M`] as a [`u64`].
+pub const SZ_16M_U64: u64 = SZ_16M as u64;
+/// [`SZ_32M`] as a [`u64`].
+pub const SZ_32M_U64: u64 = SZ_32M as u64;
+/// [`SZ_64M`] as a [`u64`].
+pub const SZ_64M_U64: u64 = SZ_64M as u64;
+/// [`SZ_128M`] as a [`u64`].
+pub const SZ_128M_U64: u64 = SZ_128M as u64;
+/// [`SZ_256M`] as a [`u64`].
+pub const SZ_256M_U64: u64 = SZ_256M as u64;
+/// [`SZ_512M`] as a [`u64`].
+pub const SZ_512M_U64: u64 = SZ_512M as u64;
+/// [`SZ_1G`] as a [`u64`].
+pub const SZ_1G_U64: u64 = SZ_1G as u64;
+/// [`SZ_2G`] as a [`u64`].
+pub const SZ_2G_U64: u64 = SZ_2G as u64;
-- 
2.53.0