The device.hints file is read in by the boot loader(8) when the system is about to start, and its contents are passed to the kernel. It contains various variables to control the boot behavior of the kernel. These variables are typically "device hints".
The file contains one variable per line. Lines starting with the # character are comments and are ignored by the boot loader.
After the file is read by the boot loader, you may examine the variables with the show command, and may add a new variable, modify an existing one, or delete a variable with the set and unset commands of the boot loader (see loader(8)).
After the system has started, you can dump these variables with the kenv(1) command.
Device hint variables are used by device drivers to set up the device. They are most often used by ISA device drivers to specify where the driver will probe for the relevant devices, and what resources it will attempt to use.
A device hint line looks like:
where driver is the name of a device driver, unit is the unit number, and keyword is the keyword of the hint. The keyword may be: