From 4c44975e98d851c2d0ded26813e0da16b9d0054e Mon Sep 17 00:00:00 2001
From: Mark Pizzolato <mark@infocomm.com>
Date: Sun, 7 Nov 2021 10:06:40 -0800
Subject: [PATCH] SCSI, VAX & PDP11: Force Read Only attach for CDROM  devices

As reported in #1094
---
 PDP11/pdp11_rq.c | 2 ++
 sim_scsi.c       | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/PDP11/pdp11_rq.c b/PDP11/pdp11_rq.c
index 4a4f7b71..6842bde2 100644
--- a/PDP11/pdp11_rq.c
+++ b/PDP11/pdp11_rq.c
@@ -2960,6 +2960,8 @@ t_stat rq_attach (UNIT *uptr, CONST char *cptr)
 MSC *cp = rq_ctxmap[uptr->cnum];
 t_stat r;
 
+if (drv_tab[GET_DTYPE (uptr->flags)].flgs & RQDF_RO)
+    sim_switches |= SWMASK ('R');
 r = sim_disk_attach_ex (uptr, cptr, RQ_NUMBY, sizeof (uint16), (uptr->flags & UNIT_NOAUTO), DBG_DSK, 
                         drv_tab[GET_DTYPE (uptr->flags)].name, 0, 0, (uptr->flags & UNIT_NOAUTO) ? NULL : drv_types);
 if (r != SCPE_OK)
diff --git a/sim_scsi.c b/sim_scsi.c
index b670d654..e2388a01 100644
--- a/sim_scsi.c
+++ b/sim_scsi.c
@@ -1706,7 +1706,9 @@ if (dev == NULL)
 switch (dev->devtype) {
     case SCSI_DISK:
     case SCSI_WORM:
+        return sim_disk_attach_ex (uptr, cptr, dev->block_size, sizeof (uint16), (uptr->flags & SCSI_NOAUTO), SCSI_DBG_DSK, dev->name, 0, 0, drivetypes);
     case SCSI_CDROM:
+        sim_switches |= SWMASK ('R');       /* Force Read Only Attach for CDROM */
         return sim_disk_attach_ex (uptr, cptr, dev->block_size, sizeof (uint16), (uptr->flags & SCSI_NOAUTO), SCSI_DBG_DSK, dev->name, 0, 0, drivetypes);
     case SCSI_TAPE:
         return sim_tape_attach_ex (uptr, cptr, SCSI_DBG_TAP, 0);