Add mtopei CSR

riscv/CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Added
 
+- Add `mtopei` CSR
 - Add `mstatus` and `sstatus` CSRs helpers for UBE, VS, UXL and SXL, and the corresponding tests
 - Add `pmpaddr16` ~ `pmpaddr63` CSRs
 - Add `siselect` CSR

riscv/src/register.rs

@@ -91,6 +91,7 @@ pub mod mepc;
 pub mod mip;
 pub mod mscratch;
 pub mod mtinst;
+pub mod mtopei;
 pub mod mtopi;
 pub mod mtval;
 pub mod mtval2;

riscv/src/register/mtopei.rs

@@ -0,0 +1,70 @@
+//! `mtopei` register — Machine Top External Interrupt (0x35C)
+//!
+//! This CSR is part of the RISC-V Advanced Interrupt Architecture (AIA). Its layout mirrors
+//! `mtopi`, exposing the interrupt identity and priority of the top pending machine external
+//! interrupt.
+
+read_write_csr! {
+    /// Machine Top External Interrupt Register
+    Mtopei: 0x35C,
+    mask: 0x0FFF_00FF,
+}
+
+read_write_csr_field! {
+    Mtopei,
+    /// Interrupt ID (bits 16..27)
+    ///
+    /// Identifies the specific interrupt source. A value of 0 indicates no interrupt is pending.
+    iid: [16:27],
+}
+
+read_write_csr_field! {
+    Mtopei,
+    /// Interrupt Priority ID (bits 0..7)
+    ///
+    /// Represents the priority level of the pending interrupt.
+    /// Lower numerical values indicate higher priority interrupts.
+    iprio: [0:7],
+}
+
+impl Mtopei {
+    /// Returns true if there is a valid interrupt pending.
+    #[inline]
+    pub fn is_interrupt_pending(&self) -> bool {
+        self.iid() != 0
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_mtopei_fields() {
+        let mut mtopei = Mtopei::from_bits(0);
+        test_csr_field!(mtopei, iid: [16, 27], 0x0);
+        test_csr_field!(mtopei, iprio: [0, 7], 0x0);
+
+        let mut mtopei = Mtopei::from_bits((0xB << 16) | 5);
+        test_csr_field!(mtopei, iid: [16, 27], 0xB);
+        test_csr_field!(mtopei, iprio: [0, 7], 0x5);
+
+        let mut mtopei = Mtopei::from_bits((0xFFF << 16) | 0xFF);
+        test_csr_field!(mtopei, iid: [16, 27], 0xFFF);
+        test_csr_field!(mtopei, iprio: [0, 7], 0xFF);
+
+        let mut mtopei = Mtopei::from_bits(1 << 16);
+        test_csr_field!(mtopei, iid: [16, 27], 0x1);
+        test_csr_field!(mtopei, iprio: [0, 7], 0x0);
+
+        let mut mtopei = Mtopei::from_bits(1);
+        test_csr_field!(mtopei, iid: [16, 27], 0x0);
+        test_csr_field!(mtopei, iprio: [0, 7], 0x1);
+    }
+
+    #[test]
+    fn test_mtopei_bitmask() {
+        let mtopei = Mtopei::from_bits(usize::MAX);
+        assert_eq!(mtopei.bits(), 0x0FFF_00FFusize);
+    }
+}