[PATCH v7 4/6] rust: io: factor out MMIO read/write macros

[Zhi Wang <zhiw@nvidia.com>]

Refactor the existing MMIO accessors to use common call macros
instead of inlining the bindings calls in each `define_{read,write}!`
expansion.

This factoring separates the common offset/bounds checks from the
low-level call pattern, making it easier to add additional I/O accessor
families.

No functional change intended.

Cc: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Zhi Wang <zhiw@nvidia.com>
---
 rust/kernel/io.rs | 149 ++++++++++++++++++++++++++++++++--------------
 1 file changed, 104 insertions(+), 45 deletions(-)

diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
index 3e6ea29835ae..6e0daaf8dc6a 100644
--- a/rust/kernel/io.rs
+++ b/rust/kernel/io.rs
@@ -137,8 +137,65 @@ pub fn maxsize(&self) -> usize {
 #[repr(transparent)]
 pub struct Mmio<const SIZE: usize = 0>(MmioRaw<SIZE>);
 
+/// Internal helper macros used to invoke C MMIO read functions.
+///
+/// This macro is intended to be used by higher-level MMIO access macros (define_read) and provides
+/// a unified expansion for infallible vs. fallible read semantics. It emits a direct call into the
+/// corresponding C helper and performs the required cast to the Rust return type.
+///
+/// # Parameters
+///
+/// * `$c_fn` – The C function performing the MMIO write.
+/// * `$self` – The I/O backend object.
+/// * `$ty` – The type of the value to be read.
+/// * `$addr` – The MMIO address to read.
+///
+/// This macro does not perform any validation; all invariants must be upheld by the higher-level
+/// abstraction invoking it.
+macro_rules! call_mmio_read {
+    (infallible, $c_fn:ident, $self:ident, $type:ty, $addr:expr) => {
+        // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
+        unsafe { bindings::$c_fn($addr as *const c_void) as $type }
+    };
+
+    (fallible, $c_fn:ident, $self:ident, $type:ty, $addr:expr) => {{
+        // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
+        Ok(unsafe { bindings::$c_fn($addr as *const c_void) as $type })
+    }};
+}
+
+/// Internal helper macros used to invoke C MMIO write functions.
+///
+/// This macro is intended to be used by higher-level MMIO access macros (define_write) and provides
+/// a unified expansion for infallible vs. fallible read semantics. It emits a direct call into the
+/// corresponding C helper and performs the required cast to the Rust return type.
+///
+/// # Parameters
+///
+/// * `$c_fn` – The C function performing the MMIO write.
+/// * `$self` – The I/O backend object.
+/// * `$ty` – The type of the written value.
+/// * `$addr` – The MMIO address to write.
+/// * `$value` – The value to write.
+///
+/// This macro does not perform any validation; all invariants must be upheld by the higher-level
+/// abstraction invoking it.
+macro_rules! call_mmio_write {
+    (infallible, $c_fn:ident, $self:ident, $ty:ty, $addr:expr, $value:expr) => {
+        // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
+        unsafe { bindings::$c_fn($value, $addr as *mut c_void) }
+    };
+
+    (fallible, $c_fn:ident, $self:ident, $ty:ty, $addr:expr, $value:expr) => {{
+        // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
+        unsafe { bindings::$c_fn($value, $addr as *mut c_void) };
+        Ok(())
+    }};
+}
+
 macro_rules! define_read {
-    (infallible, $(#[$attr:meta])* $vis:vis $name:ident, $c_fn:ident -> $type_name:ty) => {
+    (infallible, $(#[$attr:meta])* $vis:vis $name:ident, $call_macro:ident($c_fn:ident) ->
+     $type_name:ty) => {
         /// Read IO data from a given offset known at compile time.
         ///
         /// Bound checks are performed on compile time, hence if the offset is not known at compile
@@ -148,12 +205,13 @@ macro_rules! define_read {
         $vis fn $name(&self, offset: usize) -> $type_name {
             let addr = self.io_addr_assert::<$type_name>(offset);
 
-            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
-            unsafe { bindings::$c_fn(addr as *const c_void) }
+            // SAFETY: By the type invariant `addr` is a valid address for IO operations.
+            $call_macro!(infallible, $c_fn, self, $type_name, addr)
         }
     };
 
-    (fallible, $(#[$attr:meta])* $vis:vis $try_name:ident, $c_fn:ident -> $type_name:ty) => {
+    (fallible, $(#[$attr:meta])* $vis:vis $try_name:ident, $call_macro:ident($c_fn:ident) ->
+     $type_name:ty) => {
         /// Read IO data from a given offset.
         ///
         /// Bound checks are performed on runtime, it fails if the offset (plus the type size) is
@@ -162,14 +220,16 @@ macro_rules! define_read {
         $vis fn $try_name(&self, offset: usize) -> Result<$type_name> {
             let addr = self.io_addr::<$type_name>(offset)?;
 
-            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
-            Ok(unsafe { bindings::$c_fn(addr as *const c_void) })
+            // SAFETY: By the type invariant `addr` is a valid address for IO operations.
+            $call_macro!(fallible, $c_fn, self, $type_name, addr)
         }
     };
 }
+pub(crate) use define_read;
 
 macro_rules! define_write {
-    (infallible, $(#[$attr:meta])* $vis:vis $name:ident, $c_fn:ident <- $type_name:ty) => {
+    (infallible, $(#[$attr:meta])* $vis:vis $name:ident, $call_macro:ident($c_fn:ident) <-
+     $type_name:ty) => {
         /// Write IO data from a given offset known at compile time.
         ///
         /// Bound checks are performed on compile time, hence if the offset is not known at compile
@@ -179,12 +239,12 @@ macro_rules! define_write {
         $vis fn $name(&self, value: $type_name, offset: usize) {
             let addr = self.io_addr_assert::<$type_name>(offset);
 
-            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
-            unsafe { bindings::$c_fn(value, addr as *mut c_void) }
+            $call_macro!(infallible, $c_fn, self, $type_name, addr, value);
         }
     };
 
-    (fallible, $(#[$attr:meta])* $vis:vis $try_name:ident, $c_fn:ident <- $type_name:ty) => {
+    (fallible, $(#[$attr:meta])* $vis:vis $try_name:ident, $call_macro:ident($c_fn:ident) <-
+     $type_name:ty) => {
         /// Write IO data from a given offset.
         ///
         /// Bound checks are performed on runtime, it fails if the offset (plus the type size) is
@@ -193,12 +253,11 @@ macro_rules! define_write {
         $vis fn $try_name(&self, value: $type_name, offset: usize) -> Result {
             let addr = self.io_addr::<$type_name>(offset)?;
 
-            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
-            unsafe { bindings::$c_fn(value, addr as *mut c_void) }
-            Ok(())
+            $call_macro!(fallible, $c_fn, self, $type_name, addr, value)
         }
     };
 }
+pub(crate) use define_write;
 
 /// Checks whether an access of type `U` at the given `offset`
 /// is valid within this region.
@@ -339,23 +398,23 @@ fn maxsize(&self) -> usize {
 }
 
 impl<const SIZE: usize> IoInfallible for Mmio<SIZE> {
-    define_read!(infallible, read8, readb -> u8);
-    define_read!(infallible, read16, readw -> u16);
-    define_read!(infallible, read32, readl -> u32);
+    define_read!(infallible, read8, call_mmio_read(readb) -> u8);
+    define_read!(infallible, read16, call_mmio_read(readw) -> u16);
+    define_read!(infallible, read32, call_mmio_read(readl) -> u32);
 
-    define_write!(infallible, write8, writeb <- u8);
-    define_write!(infallible, write16, writew <- u16);
-    define_write!(infallible, write32, writel <- u32);
+    define_write!(infallible, write8, call_mmio_write(writeb) <- u8);
+    define_write!(infallible, write16, call_mmio_write(writew) <- u16);
+    define_write!(infallible, write32, call_mmio_write(writel) <- u32);
 }
 
 impl<const SIZE: usize> IoFallible for Mmio<SIZE> {
-    define_read!(fallible, try_read8, readb -> u8);
-    define_read!(fallible, try_read16, readw -> u16);
-    define_read!(fallible, try_read32, readl -> u32);
+    define_read!(fallible, try_read8, call_mmio_read(readb) -> u8);
+    define_read!(fallible, try_read16, call_mmio_read(readw) -> u16);
+    define_read!(fallible, try_read32, call_mmio_read(readl) -> u32);
 
-    define_write!(fallible, try_write8, writeb <- u8);
-    define_write!(fallible, try_write16, writew <- u16);
-    define_write!(fallible, try_write32, writel <- u32);
+    define_write!(fallible, try_write8, call_mmio_write(writeb) <- u8);
+    define_write!(fallible, try_write16, call_mmio_write(writew) <- u16);
+    define_write!(fallible, try_write32, call_mmio_write(writel) <- u32);
 }
 
 #[cfg(CONFIG_64BIT)]
@@ -363,16 +422,16 @@ impl<const SIZE: usize> Io64 for Mmio<SIZE> {}
 
 #[cfg(CONFIG_64BIT)]
 impl<const SIZE: usize> IoInfallible64 for Mmio<SIZE> {
-    define_read!(infallible, read64, readq -> u64);
+    define_read!(infallible, read64, call_mmio_read(readq) -> u64);
 
-    define_write!(infallible, write64, writeq <- u64);
+    define_write!(infallible, write64, call_mmio_write(writeq) <- u64);
 }
 
 #[cfg(CONFIG_64BIT)]
 impl<const SIZE: usize> IoFallible64 for Mmio<SIZE> {
-    define_read!(fallible, try_read64, readq -> u64);
+    define_read!(fallible, try_read64, call_mmio_read(readq) -> u64);
 
-    define_write!(fallible, try_write64, writeq <- u64);
+    define_write!(fallible, try_write64, call_mmio_write(writeq) <- u64);
 }
 
 impl<const SIZE: usize> Mmio<SIZE> {
@@ -387,43 +446,43 @@ pub unsafe fn from_raw(raw: &MmioRaw<SIZE>) -> &Self {
         unsafe { &*core::ptr::from_ref(raw).cast() }
     }
 
-    define_read!(infallible, pub read8_relaxed, readb_relaxed -> u8);
-    define_read!(infallible, pub read16_relaxed, readw_relaxed -> u16);
-    define_read!(infallible, pub read32_relaxed, readl_relaxed -> u32);
+    define_read!(infallible, pub read8_relaxed, call_mmio_read(readb_relaxed) -> u8);
+    define_read!(infallible, pub read16_relaxed, call_mmio_read(readw_relaxed) -> u16);
+    define_read!(infallible, pub read32_relaxed, call_mmio_read(readl_relaxed) -> u32);
     define_read!(
         infallible,
         #[cfg(CONFIG_64BIT)]
         pub read64_relaxed,
-        readq_relaxed -> u64
+        call_mmio_read(readq_relaxed) -> u64
     );
 
-    define_read!(fallible, pub try_read8_relaxed, readb_relaxed -> u8);
-    define_read!(fallible, pub try_read16_relaxed, readw_relaxed -> u16);
-    define_read!(fallible, pub try_read32_relaxed, readl_relaxed -> u32);
+    define_read!(fallible, pub try_read8_relaxed, call_mmio_read(readb_relaxed) -> u8);
+    define_read!(fallible, pub try_read16_relaxed, call_mmio_read(readw_relaxed) -> u16);
+    define_read!(fallible, pub try_read32_relaxed, call_mmio_read(readl_relaxed) -> u32);
     define_read!(
         fallible,
         #[cfg(CONFIG_64BIT)]
         pub try_read64_relaxed,
-        readq_relaxed -> u64
+        call_mmio_read(readq_relaxed) -> u64
     );
 
-    define_write!(infallible, pub write8_relaxed, writeb_relaxed <- u8);
-    define_write!(infallible, pub write16_relaxed, writew_relaxed <- u16);
-    define_write!(infallible, pub write32_relaxed, writel_relaxed <- u32);
+    define_write!(infallible, pub write8_relaxed, call_mmio_write(writeb_relaxed) <- u8);
+    define_write!(infallible, pub write16_relaxed, call_mmio_write(writew_relaxed) <- u16);
+    define_write!(infallible, pub write32_relaxed, call_mmio_write(writel_relaxed) <- u32);
     define_write!(
         infallible,
         #[cfg(CONFIG_64BIT)]
         pub write64_relaxed,
-        writeq_relaxed <- u64
+        call_mmio_write(writeq_relaxed) <- u64
     );
 
-    define_write!(fallible, pub try_write8_relaxed, writeb_relaxed <- u8);
-    define_write!(fallible, pub try_write16_relaxed, writew_relaxed <- u16);
-    define_write!(fallible, pub try_write32_relaxed, writel_relaxed <- u32);
+    define_write!(fallible, pub try_write8_relaxed, call_mmio_write(writeb_relaxed) <- u8);
+    define_write!(fallible, pub try_write16_relaxed, call_mmio_write(writew_relaxed) <- u16);
+    define_write!(fallible, pub try_write32_relaxed, call_mmio_write(writel_relaxed) <- u32);
     define_write!(
         fallible,
         #[cfg(CONFIG_64BIT)]
         pub try_write64_relaxed,
-        writeq_relaxed <- u64
+        call_mmio_write(writeq_relaxed) <- u64
     );
 }
-- 
2.51.0