My trusty old VDR box started behaving erratically: sometimes the IR remote didn’t do anything. Rebooting the whole box usually helped, but not always. Eventually I was able to narrow the problem down: for some reason the LIRC serial driver did not correctly detect the IR receiver in the serial port at the boot. I don’t have any idea why that happened and why it started only recently. But, I was able to figure out a workaround where the lirc_serial module was reloaded later in the Linux boot process. This is my documentation about the implementation.
First, /usr/local/bin/lirc_serial_reload.sh is the script that does the actual work:
#!/bin/bash
systemctl stop lircd.socket
systemctl stop lircd.service
rmmod lirc_serial
modprobe lirc_serial
systemctl start lircd.socket
systemctl start lircd.service
The interesting part was to figure out how to run that once during the boot process. On this Debian 9 Stretch system systemd is responsible for running all the startup scripts, so I found out the oneshot service type and created the configuration in /etc/systemd/system/lircserialrestart.service:
[Unit]
Description=lirc_serial restart, by Markku
After=lircd.service
Before=vdr.service
[Service]
Type=oneshot
ExecStart=/usr/local/bin/lirc_serial_reload.sh
[Install]
WantedBy=multi-user.target
Basically, it defines that the service is only run once (Type=oneshot), it is to be run after LIRC daemon (because it stops and later starts the daemon again) but before VDR.
And finally the service was enabled with systemctl daemon-reload and systemctl enable lircserialrestart.service commands.