Merge pull request #232 from rmsyn/riscv/marchid-csr-macro

riscv: define marchid using CSR macros

Author: jessebraham

Diff for: riscv/CHANGELOG.md

@@ -7,6 +7,14 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+### Added
+
+- CSR helper macro to check for platform implementation
+
+### Changed
+
+- Use CSR helper macros to define `marchid` register
+
 ## [v0.12.1] - 2024-10-20
 
 ### Changed

Diff for: riscv/src/register/macros.rs

@@ -92,6 +92,27 @@ macro_rules! read_csr_as {
             })
         }
     };
+
+    ($register:ident, $csr_number:literal, $sentinel:tt) => {
+        $crate::read_csr!($csr_number);
+
+        /// Reads the CSR.
+        ///
+        /// **WARNING**: panics on targets not implementing this CSR.
+        #[inline]
+        pub fn read() -> $register {
+            try_read().unwrap()
+        }
+
+        /// Attempts to reads the CSR.
+        #[inline]
+        pub fn try_read() -> $crate::result::Result<$register> {
+            match unsafe { _try_read()? } {
+                $sentinel => Err($crate::result::Error::Unimplemented),
+                bits => Ok($register { bits }),
+            }
+        }
+    };
 }
 
 /// `RV32`: Convenience macro to read a CSR register value as a `register` type.
@@ -732,6 +753,16 @@ macro_rules! read_only_csr {
 
         $crate::read_csr_as!($ty, $csr);
     };
+
+    ($(#[$doc:meta])+
+     $ty:ident: $csr:tt,
+     mask: $mask:tt,
+     sentinel: $sentinel:tt$(,)?,
+    ) => {
+        $crate::csr! { $(#[$doc])+ $ty, $mask }
+
+        $crate::read_csr_as!($ty, $csr, $sentinel);
+    };
 }
 
 /// Helper macro to create a read-only CSR type.

Diff for: riscv/src/register/marchid.rs

@@ -1,28 +1,8 @@
 //! marchid register
 
-use core::num::NonZeroUsize;
-
-/// marchid register
-#[derive(Clone, Copy, Debug)]
-pub struct Marchid {
-    bits: NonZeroUsize,
-}
-
-impl Marchid {
-    /// Returns the contents of the register as raw bits
-    #[inline]
-    pub fn bits(&self) -> usize {
-        self.bits.get()
-    }
-}
-
-read_csr!(0xF12);
-
-/// Reads the CSR
-#[inline]
-pub fn read() -> Option<Marchid> {
-    let r = unsafe { _read() };
-    // When marchid is hardwired to zero it means that the marchid
-    // csr isn't implemented.
-    NonZeroUsize::new(r).map(|bits| Marchid { bits })
+read_only_csr! {
+    /// `marchid` register
+    Marchid: 0xF12,
+    mask: 0xffff_ffff,
+    sentinel: 0,
 }