From aa9cca4e2182bca1fd0b0e6caadb80e8feb16ae6 Mon Sep 17 00:00:00 2001
From: Scott Moser <smoser@brickies.net>
Date: Wed, 6 Aug 2025 17:24:50 -0400
Subject: [PATCH] Support loading cdrom modules before reading blkid info.

If scsi cdrom module is not built in, then cdrom device might
not be present before blkid is run.  The result would be that
cdrom based datasources (ConfigDrive, NoCloud, OVF) may not
be found.

Add support for local setting of modification of PROBE_CDROM_MODULES
varible.  Each module in this list will be modprobed
and then udevadm will be settled afterwards.

Other things here:
1. fix for probe_floppy path that would fail with unset variable.
2. add debugts function for debug with timestamp.

Upstream PR https://github.com/canonical/cloud-init/pull/6364
---
 tools/ds-identify | 51 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/tools/ds-identify b/tools/ds-identify
index b531cfd0d46..3e77cfefb86 100755
--- a/tools/ds-identify
+++ b/tools/ds-identify
@@ -140,6 +140,11 @@ DI_ON_NOTFOUND=""
 
 DI_EC2_STRICT_ID_DEFAULT="true"
 
+STATE_CDROM_PROBED=""
+STATE_FLOPPY_PROBED=""
+
+# PROBE_CDROM_MODULES - modules will be modprobed if /dev/cdrom does not exist.
+PROBE_CDROM_MODULES=""
 _IS_IBM_CLOUD=""
 
 error() {
@@ -304,6 +309,7 @@ ensure_sane_path() {
 blkid_export() {
     # call 'blkid -c /dev/null export', set DI_BLKID_EXPORT_OUT
     cached "$DI_BLKID_EXPORT_OUT" && return 0
+    probe_cdrom
     local out="" ret=0
     out=$(blkid -c /dev/null -o export) && DI_BLKID_EXPORT_OUT="$out" || {
         ret=$?
@@ -763,6 +769,51 @@ check_writable_seed_dir() {
     check_seed_dir "$@"
 }
 
+debugts() {
+    local lvl="$1"
+    shift
+    [ "$lvl" -gt "${DI_DEBUG_LEVEL}" ] && return
+    read_uptime
+    debug "$lvl" "[up ${_RET}s]" "$@"
+}
+
+probe_cdrom() {
+    cached "${STATE_CDROM_PROBED}" && return "${STATE_CDROM_PROBED}"
+    if [ -z "$PROBE_CDROM_MODULES" ]; then
+        STATE_CDROM_PROBED=1
+        return 0
+    fi
+
+    local fpath=/dev/cdrom
+    if [ -b "$fpath" ]; then
+        STATE_CDROM_PROBED=1;
+        debug 1 "$fpath existed before probe_cdrom"
+        return 0;
+    fi
+
+    debugts 1 "attempting modprobe of ${PROBE_CDROM_MODULES}"
+    local m="" modfails=""
+    for m in ${PROBE_CDROM_MODULES}; do
+        modprobe -b "$m" >/dev/null 2>&1 || modfails="${modfails:+$modfails }$m:$?"
+    done
+    [ -z "$modfails" ] ||
+        debug 1 "probe_cdrom modprobe had unsuccessful attempts: $modfails"
+
+    # Some Linux distros/non-Linux OSes may not have udev
+    if command -v udevadm >/dev/null 2>&1; then
+        debugts 1 "udev settling for $fpath"
+        if ! udevadm settle "--exit-if-exists=$fpath"; then
+            debugts 1 "udevadm settle returned $?"
+            return 1
+        fi
+        debugts 1 "udev settled for $fpath"
+    fi
+
+    [ -b "$fpath" ]
+    STATE_CDROM_PROBED=$?
+    return "${STATE_CDROM_PROBED}"
+}
+
 probe_floppy() {
     cached "${STATE_FLOPPY_PROBED}" && return "${STATE_FLOPPY_PROBED}"
     local fpath=/dev/floppy