If the device is non-self-identifying, the kernel requires a hardware configuration file for it. If the driver is called xx, the hardware configuration file for it should be called xx.conf. See driver.conf(4), pseudo(4), sbus(4), scsi(4), and vme(4) for more information on hardware configuration files. On the Intel platform, device information is now supplied by the booting system. Hardware configuration files should no longer be needed to provide probe(9E) arguments, even for non-self-identifying devices.
Arbitrary properties can be defined in hardware configuration files by adding entries of the form property=value, where property is the property name, and value is its initial value. This allows devices to be configured by changing the property values.