Scan both dmesg.boot and dmesg(8) output for devices

This allows us to detect newly plugged in devices that need firmware
added while still making sure to detect devices available at boot
even if dmesg rolls over with noisy messages.

fixes and ok kn@
I think this is good deraadt@

usr.sbin/fw_update/fw_update.8

@@ -1,4 +1,4 @@
-.\" $OpenBSD: fw_update.8,v 1.8 2025/03/22 19:51:29 jmc Exp $
+.\" $OpenBSD: fw_update.8,v 1.9 2025/12/26 18:19:46 afresh1 Exp $
 .\"
 .\" Copyright (c) 2011 Alexander Hall <alexander@beard.se>
 .\"
@@ -14,7 +14,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: March 22 2025 $
+.Dd $Mdocdate: December 26 2025 $
 .Dt FW_UPDATE 8
 .Os
 .Sh NAME
@@ -59,11 +59,11 @@ If used in conjunction with
 .Fl a ,
 delete firmware for all drivers.
 .It Fl D Ar path
-Use the
-.Xr dmesg 8
-output from
+Use the content of
 .Ar path
-rather than
+rather than output from 
+.Xr dmesg 8
+and
 .Pa /var/run/dmesg.boot
 to determine which firmware are needed.
 .It Fl F

usr.sbin/fw_update/fw_update.sh

@@ -1,5 +1,5 @@
 #!/bin/ksh
-#	$OpenBSD: fw_update.sh,v 1.65 2025/05/12 23:48:12 afresh1 Exp $
+#	$OpenBSD: fw_update.sh,v 1.66 2025/12/26 18:19:46 afresh1 Exp $
 #
 # Copyright (c) 2021,2023 Andrew Hewus Fresh <afresh1@openbsd.org>
 #
@@ -239,12 +239,25 @@ verify_existing() {
 }
 
 devices_in_dmesg() {
+	if [ "${DMESG:-}" ]; then
+		_devices_in_dmesg "$DMESG"
+		return
+	fi
+
+	dmesg > "$FD_DIR/dmesg"
+	
+	_devices_in_dmesg /var/run/dmesg.boot
+	_devices_in_dmesg "$FD_DIR/dmesg"
+}
+
+_devices_in_dmesg() {
+	local _dmesg=$1
 	local IFS
 	local _d _m _dmesgtail _last='' _nl='
 '
 
 	# The dmesg can contain multiple boots, only look in the last one
-	_dmesgtail="$( echo ; sed -n 'H;/^OpenBSD/h;${g;p;}' "$DMESG" )"
+	_dmesgtail="$( echo ; sed -n 'H;/^OpenBSD/h;${g;p;}' "$_dmesg" )"
 
 	grep -v '^[[:space:]]*#' "$FWPATTERNS" |
 	    while read -r _d _m; do
@@ -489,7 +502,7 @@ set_fw_paths() {
 	if [ ! "$_version" ]; then
 		_version=$(sed -nE \
 		    '/^OpenBSD ([0-9]+\.[0-9][^ ]*) .*/{s//\1/;h;};${g;p;}' \
-		    "$DMESG")
+		    "${DMESG:-/var/run/dmesg.boot}")
 	
 		# If VNAME was set in the environment instead of the DMESG,
 		# looking in the DMESG for "current" is wrong.
@@ -514,7 +527,6 @@ usage() {
 
 ALL=false
 LIST=false
-DMESG=/var/run/dmesg.boot
 
 while getopts :adD:Flnp:v name
 do
@@ -561,7 +573,7 @@ if [ "${FWURL:-}" ] && ! "$INSTALL" ; then
 	usage
 fi
 
-if [ ! -s "$DMESG" ]; then
+if [ "${DMESG:-}" ] && [ ! -s "$DMESG" ]; then
 	warn "${0##*/}: $DMESG: No such file or directory"
 	exit 1
 fi