[RFC 2/6] 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.

Signed-off-by: Zhi Wang <zhiw@nvidia.com>
---
 rust/kernel/io.rs | 67 +++++++++++++++++++++++++++++------------------
 1 file changed, 42 insertions(+), 25 deletions(-)

diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
index f4727f3b954e..8d67d46777db 100644
--- a/rust/kernel/io.rs
+++ b/rust/kernel/io.rs
@@ -112,8 +112,22 @@ pub fn maxsize(&self) -> usize {
 #[repr(transparent)]
 pub struct Io<const SIZE: usize = 0>(IoRaw<SIZE>);
 
+macro_rules! call_mmio_read {
+    ($c_fn:ident, $self:ident, $offset:expr, $type:ty, $addr:expr) => {
+        // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
+        unsafe { bindings::$c_fn($addr as *const c_void) }
+    };
+}
+
+macro_rules! call_mmio_write {
+    ($c_fn:ident, $self:ident, $offset:expr, $ty:ty, $addr:expr, $value:expr) => {
+        // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
+        unsafe { bindings::$c_fn($value, $addr as *mut c_void) }
+    };
+}
+
 macro_rules! define_read {
-    ($(#[$attr:meta])* $name:ident, $try_name:ident, $c_fn:ident -> $type_name:ty) => {
+    ($(#[$attr:meta])* $name:ident, $try_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
@@ -121,10 +135,9 @@ macro_rules! define_read {
         $(#[$attr])*
         #[inline]
         pub fn $name(&self, offset: usize) -> $type_name {
-            let addr = self.io_addr_assert::<$type_name>(offset);
+            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) }
+            $call_macro!($c_fn, self, offset, $type_name, _addr)
         }
 
         /// Read IO data from a given offset.
@@ -133,16 +146,17 @@ pub fn $name(&self, offset: usize) -> $type_name {
         /// out of bounds.
         $(#[$attr])*
         pub fn $try_name(&self, offset: usize) -> Result<$type_name> {
-            let addr = self.io_addr::<$type_name>(offset)?;
+            let _addr = self.io_addr::<$type_name>(offset)?;
 
             // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
-            Ok(unsafe { bindings::$c_fn(addr as *const c_void) })
+            Ok($call_macro!($c_fn, self, offset, $type_name, _addr))
         }
     };
 }
+pub(crate) use define_read;
 
 macro_rules! define_write {
-    ($(#[$attr:meta])* $name:ident, $try_name:ident, $c_fn:ident <- $type_name:ty) => {
+    ($(#[$attr:meta])* $name:ident, $try_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
@@ -150,10 +164,9 @@ macro_rules! define_write {
         $(#[$attr])*
         #[inline]
         pub fn $name(&self, value: $type_name, offset: usize) {
-            let addr = self.io_addr_assert::<$type_name>(offset);
+            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) }
+            $call_macro!($c_fn, self, offset, $type_name, _addr, value)
         }
 
         /// Write IO data from a given offset.
@@ -162,14 +175,14 @@ pub fn $name(&self, value: $type_name, offset: usize) {
         /// out of bounds.
         $(#[$attr])*
         pub fn $try_name(&self, value: $type_name, offset: usize) -> Result {
-            let addr = self.io_addr::<$type_name>(offset)?;
+            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) }
+            $call_macro!($c_fn, self, offset, $type_name, _addr, value);
             Ok(())
         }
     };
 }
+pub(crate) use define_write;
 
 /// Represents a region of I/O space of a fixed size.
 ///
@@ -246,43 +259,47 @@ pub unsafe fn from_raw(raw: &IoRaw<SIZE>) -> &Self {
         unsafe { &*core::ptr::from_ref(raw).cast() }
     }
 
-    define_read!(read8, try_read8, readb -> u8);
-    define_read!(read16, try_read16, readw -> u16);
-    define_read!(read32, try_read32, readl -> u32);
+    define_read!(read8, try_read8, call_mmio_read, readb -> u8);
+    define_read!(read16, try_read16, call_mmio_read, readw -> u16);
+    define_read!(read32, try_read32, call_mmio_read, readl -> u32);
     define_read!(
         #[cfg(CONFIG_64BIT)]
         read64,
         try_read64,
+        call_mmio_read,
         readq -> 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);
+    define_read!(read8_relaxed, try_read8_relaxed, call_mmio_read, readb_relaxed -> u8);
+    define_read!(read16_relaxed, try_read16_relaxed, call_mmio_read, readw_relaxed -> u16);
+    define_read!(read32_relaxed, try_read32_relaxed, call_mmio_read, readl_relaxed -> u32);
     define_read!(
         #[cfg(CONFIG_64BIT)]
         read64_relaxed,
         try_read64_relaxed,
+        call_mmio_read,
         readq_relaxed -> u64
     );
 
-    define_write!(write8, try_write8, writeb <- u8);
-    define_write!(write16, try_write16, writew <- u16);
-    define_write!(write32, try_write32, writel <- u32);
+    define_write!(write8, try_write8, call_mmio_write, writeb <- u8);
+    define_write!(write16, try_write16, call_mmio_write, writew <- u16);
+    define_write!(write32, try_write32, call_mmio_write, writel <- u32);
     define_write!(
         #[cfg(CONFIG_64BIT)]
         write64,
         try_write64,
+        call_mmio_write,
         writeq <- 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);
+    define_write!(write8_relaxed, try_write8_relaxed, call_mmio_write, writeb_relaxed <- u8);
+    define_write!(write16_relaxed, try_write16_relaxed, call_mmio_write, writew_relaxed <- u16);
+    define_write!(write32_relaxed, try_write32_relaxed, call_mmio_write, writel_relaxed <- u32);
     define_write!(
         #[cfg(CONFIG_64BIT)]
         write64_relaxed,
         try_write64_relaxed,
+        call_mmio_write,
         writeq_relaxed <- u64
     );
 }
-- 
2.47.3