From c98ad84171f06147318d11f45b29adb83fa5f89d Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Wed, 25 Dec 2024 20:25:25 +0100
Subject: [PATCH] SB: Fix CT1475 even port read and return 0xFF on it and ports
 227h and 22Bh which are tested for noise by OS/2 Warp 4.0, fixes the OS/2
 Warp 4.0 hang on SB PNP's and AWE 32.

---
 src/sound/snd_sb.c     | 7 +++----
 src/sound/snd_sb_dsp.c | 8 ++++++++
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/sound/snd_sb.c b/src/sound/snd_sb.c
index 0ecc39bd5..05cd16d0f 100644
--- a/src/sound/snd_sb.c
+++ b/src/sound/snd_sb.c
@@ -1177,12 +1177,11 @@ sb_ct1745_mixer_read(uint16_t addr, void *priv)
     const sb_ct1745_mixer_t *mixer = &sb->mixer_sb16;
     uint8_t                  ret = 0xff;
 
-    if (!(addr & 1))
-        ret = mixer->index;
-
     sb_log("sb_ct1745: received register READ: %02X\t%02X\n", mixer->index, mixer->regs[mixer->index]);
 
-    if ((mixer->index >= 0x30) && (mixer->index <= 0x47))
+    if (!(addr & 1))
+        ret = 0xff /*mixer->index*/;
+    else if ((mixer->index >= 0x30) && (mixer->index <= 0x47))
         ret = mixer->regs[mixer->index];
     else {
         switch (mixer->index) {
diff --git a/src/sound/snd_sb_dsp.c b/src/sound/snd_sb_dsp.c
index 0063f0ae7..2cabde8cc 100644
--- a/src/sound/snd_sb_dsp.c
+++ b/src/sound/snd_sb_dsp.c
@@ -1938,6 +1938,14 @@ sb_read(uint16_t a, void *priv)
             } else
                 ret = 0xff;
             break;
+        case 0x7:
+        case 0xB:
+            /*
+               These two ports are tested for random noise by OS/2 Warp 4.0, so
+               return 0xff to get through said test.
+             */
+            ret = 0xff;
+            break;
         case 0xA: /* Read data */
             if (dsp->mpu && dsp->uart_midi)
                 ret = MPU401_ReadData(dsp->mpu);