riscv: add basic mvendorid unit tests

Adds basic unit tests for the `mvendorid` CSR.

riscv/src/register/mvendorid.rs

@@ -24,6 +24,9 @@ read_only_csr_field! {
 }
 
 impl Mvendorid {
+    /// Represents the JEDEC manufacture continuation byte.
+    pub const CONTINUATION: u8 = 0x7f;
+
     /// Gets the decoded JEDEC manufacturer ID from the `mvendorid` value.
     ///
     /// # Note
@@ -34,8 +37,6 @@ impl Mvendorid {
     ///
     /// The final byte in the iterator is the `offset`, including the odd parity bit (set only if even).
     pub fn jedec_manufacturer(&self) -> impl Iterator<Item = u8> {
-        const CONTINUATION: u8 = 0x7f;
-
         let mut done = false;
         let mut bank = self.bank();
         let offset = self.offset();
@@ -49,8 +50,50 @@ impl Mvendorid {
             }
             _ => {
                 bank -= 1;
-                Some(CONTINUATION)
+                Some(Self::CONTINUATION)
             }
         })
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_mvendorid() {
+        (0..u32::BITS)
+            .map(|r| ((1u64 << r) - 1) as usize)
+            .for_each(|raw| {
+                let exp_bank = raw >> 7;
+                let exp_offset = raw & 0x7f;
+                let exp_parity = (1 - (exp_offset % 2)) << 7;
+                let exp_mvendorid = Mvendorid::from_bits(raw);
+
+                assert_eq!(exp_mvendorid.bank(), exp_bank);
+                assert_eq!(exp_mvendorid.offset(), exp_offset);
+
+                let mut jedec_iter = exp_mvendorid.jedec_manufacturer();
+                (0..exp_bank)
+                    .for_each(|_| assert_eq!(jedec_iter.next(), Some(Mvendorid::CONTINUATION)));
+                assert_eq!(jedec_iter.next(), Some((exp_parity | exp_offset) as u8));
+                assert_eq!(jedec_iter.next(), None);
+            });
+
+        // ISA example used as a concrete test vector.
+
+        let exp_bank = 0xc;
+        let exp_offset = 0x0a;
+        let exp_decoded_offset = 0x8a;
+        let raw_mvendorid = 0x60a;
+        let exp_mvendorid = Mvendorid::from_bits(raw_mvendorid);
+
+        assert_eq!(exp_mvendorid.bank(), exp_bank);
+        assert_eq!(exp_mvendorid.offset(), exp_offset);
+
+        let mut jedec_iter = exp_mvendorid.jedec_manufacturer();
+        (0..exp_bank).for_each(|_| assert_eq!(jedec_iter.next(), Some(Mvendorid::CONTINUATION)));
+        assert_eq!(jedec_iter.next(), Some(exp_decoded_offset));
+        assert_eq!(jedec_iter.next(), None);
+    }
+}