At end of 1995 I bought a new computer, a Pentium with a PCI BUS and wanted a PCI ethernet card. I choose a NE2000 but unfortunately the one I got was not recognized by linux and I had to hack the ne2000 driver.
I started to add some printk instructions to understand what was going wrong, and some reboot later, I got it ! An id ( probably the PCI id ) returned by the card was unknown by the driver ! I had to bypass the test and the card was recognized, and worked fine ! I got it.