From 27e6eb4c09f16f2984f2a506ad6d190333193790 Mon Sep 17 00:00:00 2001
From: rmsyn <github@weathered-steel.dev>
Date: Mon, 13 Jan 2025 23:19:19 +0000
Subject: [PATCH] riscv: re-add Mvendorid::jedec_manufacturer implementation

Adds a corrected `Mvendorid::jedec_manufacturer` implementation to
return the decoded JEDEC manufacturer ID.
---
 riscv/src/register/mvendorid.rs | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/riscv/src/register/mvendorid.rs b/riscv/src/register/mvendorid.rs
index fc6c1f33..88b03fe3 100644
--- a/riscv/src/register/mvendorid.rs
+++ b/riscv/src/register/mvendorid.rs
@@ -22,3 +22,35 @@ read_only_csr_field! {
     /// The encoded value returned by `offset` does not include the odd parity bit (`0x80`).
     offset: [0:6],
 }
+
+impl Mvendorid {
+    /// Gets the decoded JEDEC manufacturer ID from the `mvendorid` value.
+    ///
+    /// # Note
+    ///
+    /// This function returns an iterator over the decoded bytes.
+    ///
+    /// An iterator is needed because the encoding can theoretically return a max count (`0x1ff_ffff`) of continuation bytes (`0x7f`).
+    ///
+    /// 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();
+        let parity = (1 - (offset % 2)) << 7;
+
+        core::iter::from_fn(move || match bank {
+            0 if done => None,
+            0 => {
+                done = true;
+                Some((parity | offset) as u8)
+            }
+            _ => {
+                bank -= 1;
+                Some(CONTINUATION)
+            }
+        })
+    }
+}