rules: Limit the number of device units generated for serial ttys

daandemeyer · bluca · commit dc38f9addd04 · 2024-06-12T00:09:26.000+01:00
As per the suggestion in systemd#33242. This reduces the number of /dev/ttySXX device units generated in mkosi from 32 to 4.
diff --git a/rules.d/99-systemd.rules.in b/rules.d/99-systemd.rules.in
@@ -10,6 +10,8 @@
 ACTION=="remove", GOTO="systemd_end"
 
 SUBSYSTEM=="tty", KERNEL=="tty[a-zA-Z]*|hvc*|xvc*|hvsi*|ttysclp*|sclp_line*|3270/tty[0-9]*", TAG+="systemd"
+# Exclude 8250 serial ports with a zero IO port, as they are not usable until "setserial /dev/ttySxxx port …" is invoked.
+SUBSYSTEM=="tty", KERNEL=="ttyS*", DRIVERS=="serial8250", ATTR{port}=="0x0", ENV{SYSTEMD_READY}="0"
 KERNEL=="vport*", TAG+="systemd"
 
 SUBSYSTEM=="ptp", TAG+="systemd"
