From 91ca927618794df7b6867e9ee08ed6eb45cf4587 Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Fri, 2 Feb 2024 05:30:11 +0100
Subject: [PATCH] AT NVR: The ability to lock reading of a register in
 preparation of the WD7C610 rewrite.

---
 src/nvr_at.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/nvr_at.c b/src/nvr_at.c
index c66799579..7e356f55d 100644
--- a/src/nvr_at.c
+++ b/src/nvr_at.c
@@ -692,7 +692,7 @@ nvr_read(uint16_t addr, void *priv)
 {
     nvr_t         *nvr   = (nvr_t *) priv;
     const local_t *local = (local_t *) nvr->data;
-    uint8_t        ret;
+    uint8_t        ret = 0xff;
     uint8_t        addr_id = (addr & 0x0e) >> 1;
     uint16_t       i;
     uint16_t       checksum = 0x0000;
@@ -810,7 +810,8 @@ nvr_read(uint16_t addr, void *priv)
                 break;
 
             default:
-                ret = nvr->regs[local->addr[addr_id]];
+                if (!(local->lock[local->addr[addr_id]] & 0x02))
+                    ret = nvr->regs[local->addr[addr_id]];
                 break;
         }
     else {