modemmanager: do not cache virtual device events

On small systems with many virtual devices, the modem manager sometimes
could not start because it took too long until all devices for the modem
were recognised. This is because all system events that are stored in
the file events.cache have to be processed. To speed up the processing,
all devices under /sys/devices/virtual are now filtered out so that they
do not have to be processed.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>
(cherry picked from commit e66fead6d4)

net/modemmanager/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=modemmanager
 PKG_SOURCE_VERSION:=1.20.6
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://gitlab.freedesktop.org/mobile-broadband/ModemManager.git

net/modemmanager/files/modemmanager.common

@@ -273,6 +273,14 @@ mm_report_event() {
 	local subsystem="$3"
 	local sysfspath="$4"
 
+	# Do not save virtual devices
+	local virtual
+	virtual="$(echo "$sysfspath" | cut -d'/' -f4)"
+	[ "$virtual" = "virtual" ] && {
+		mm_log "debug" "sysfspath is a virtual device ($sysfspath)"
+		return
+	}
+
 	# Track/untrack events in cache
 	case "${action}" in
 		"add")