I recently installed Ubuntu 18.04 on my nearly 10 years old NAS Intel SS4200. After upgrading from Ubuntu 11.04 the harddisk LEDs stopped working and the boot log just showed an Oops when the leds_ss4200 driver was loaded.
After some investigation which involved compiling the module by myself and adding a lot of debug I found out that the pci_register_driver didn’t run the drivers install function but the later code assumed that a global pointer was filled and ready to be used. This led to the Oops. It quickly turned out that the lpc_ich already claimed the PCI id so that the leds_ss4200 wasn’t used. Solution: I disabled the lpc_ich module in the /etc/modprobe.d/blacklist.conf file and the LEDs start working again on kernel 4.15.