linux-kernel - [PATCH v2 1/4] rust: io: Add big-endian read and write functions

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Message-ID: <20260204040505.8447-2-linkmauve@linkmauve.fr>
Date: Wed,  4 Feb 2026 05:04:58 +0100
From: Link Mauve <linkmauve@...kmauve.fr>
To: rust-for-linux@...r.kernel.org
Cc: Link Mauve <linkmauve@...kmauve.fr>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	"Christophe Leroy (CS GROUP)" <chleroy@...nel.org>,
	Srinivas Kandagatla <srini@...nel.org>,
	Miguel Ojeda <ojeda@...nel.org>,
	Boqun Feng <boqun@...nel.org>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <lossin@...nel.org>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>,
	Daniel Almeida <daniel.almeida@...labora.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Eric Biggers <ebiggers@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Lyude Paul <lyude@...hat.com>,
	Asahi Lina <lina+kernel@...hilina.net>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Tamir Duberstein <tamird@...nel.org>,
	FUJITA Tomonori <fujita.tomonori@...il.com>,
	linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org,
	officialTechflashYT@...il.com,
	Ash Logan <ash@...quark.com>,
	Roberto Van Eeden <rw-r-r-0644@...tonmail.com>,
	Jonathan Neuschäfer <j.neuschaefer@....net>
Subject: [PATCH v2 1/4] rust: io: Add big-endian read and write functions

Another option would be to call u32::swap_bytes() on the data being
read/written, but these helpers make the Rust code as ergonomic as the C
code.

Signed-off-by: Link Mauve <linkmauve@...kmauve.fr>
---
 rust/helpers/io.c | 34 ++++++++++++++++++++++++++++++++++
 rust/kernel/io.rs | 18 ++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/rust/helpers/io.c b/rust/helpers/io.c
index c475913c69e6..514ad0377327 100644
--- a/rust/helpers/io.c
+++ b/rust/helpers/io.c
@@ -40,6 +40,23 @@ u64 rust_helper_readq(const void __iomem *addr)
 }
 #endif
 
+u16 rust_helper_ioread16be(const void __iomem *addr)
+{
+	return ioread16be(addr);
+}
+
+u32 rust_helper_ioread32be(const void __iomem *addr)
+{
+	return ioread32be(addr);
+}
+
+#ifdef CONFIG_64BIT
+u64 rust_helper_ioread64be(const void __iomem *addr)
+{
+	return ioread64be(addr);
+}
+#endif
+
 void rust_helper_writeb(u8 value, void __iomem *addr)
 {
 	writeb(value, addr);
@@ -62,6 +79,23 @@ void rust_helper_writeq(u64 value, void __iomem *addr)
 }
 #endif
 
+void rust_helper_iowrite16be(u16 value, void __iomem *addr)
+{
+	iowrite16be(value, addr);
+}
+
+void rust_helper_iowrite32be(u32 value, void __iomem *addr)
+{
+	iowrite32be(value, addr);
+}
+
+#ifdef CONFIG_64BIT
+void rust_helper_iowrite64be(u64 value, void __iomem *addr)
+{
+	iowrite64be(value, addr);
+}
+#endif
+
 u8 rust_helper_readb_relaxed(const void __iomem *addr)
 {
 	return readb_relaxed(addr);
diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
index 98e8b84e68d1..e6912e7ff036 100644
--- a/rust/kernel/io.rs
+++ b/rust/kernel/io.rs
@@ -256,6 +256,15 @@ fn io_addr_assert<U>(&self, offset: usize) -> usize {
         readq -> u64
     );
 
+    define_read!(read16be, try_read16be, ioread16be -> u16);
+    define_read!(read32be, try_read32be, ioread32be -> u32);
+    define_read!(
+        #[cfg(CONFIG_64BIT)]
+        read64be,
+        try_read64be,
+        ioread64be -> u64
+    );
+
     define_read!(read8_relaxed, try_read8_relaxed, readb_relaxed -> u8);
     define_read!(read16_relaxed, try_read16_relaxed, readw_relaxed -> u16);
     define_read!(read32_relaxed, try_read32_relaxed, readl_relaxed -> u32);
@@ -276,6 +285,15 @@ fn io_addr_assert<U>(&self, offset: usize) -> usize {
         writeq <- u64
     );
 
+    define_write!(write16be, try_write16be, iowrite16be <- u16);
+    define_write!(write32be, try_write32be, iowrite32be <- u32);
+    define_write!(
+        #[cfg(CONFIG_64BIT)]
+        write64be,
+        try_write64be,
+        iowrite64be <- u64
+    );
+
     define_write!(write8_relaxed, try_write8_relaxed, writeb_relaxed <- u8);
     define_write!(write16_relaxed, try_write16_relaxed, writew_relaxed <- u16);
     define_write!(write32_relaxed, try_write32_relaxed, writel_relaxed <- u32);
-- 
2.52.0