The
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 HINTS
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:
at
specifies a bus to which the device is attached.
port
specifies the start address of I/O ports to be used by the device.
portsize
specifies the number of ports used by the device.
irq
is the interrupt line number to be used.
drq
is the DMA channel number.
maddr
specifies the physical memory address used by the device.
msize
specifies the physical memory size used by the device.
flags
sets various flag bits for the device.
disabled
can be set to
Qq 1
to disable the device.
A device driver may require one or more hint lines with these keywords,
and may accept other keywords not listed here.
Consult individual device drivers' manual pages for available
keywords and their possible values.
FILES
/boot/device.hints
Device resource hints file.
/sys/ ARCH /conf/GENERIC.hints
Sample resource hints for the
GENERIC
kernel.
/sys/ ARCH /conf/NOTES
Notes on the kernel configuration file and device resource hints.
EXAMPLES
The following example sets up resources for the
sio(4)
driver on the ISA bus:
