DEVICE.HINTS(5) 					      BSD File Formats Manual						   DEVICE.HINTS(5)

NAME

     device.hints -- device resource hints

DESCRIPTION

     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 con-
     tains 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 exist-
     ing 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:

	   hint.driver.unit.keyword="value"

     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 "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, through
     resource_int_value(9).  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:

	   hint.sio.0.at="isa"
	   hint.sio.0.port="0x3F8"
	   hint.sio.0.flags="0x10"
	   hint.sio.0.irq="4"

     The following example disables the ACPI driver:

	   hint.acpi.0.disabled="1"

SEE ALSO

     kenv(1), loader.conf(5), loader(8), resource_int_value(9)

HISTORY

     The device.hints file first appeared in FreeBSD 5.0.

BSD
								September 11, 2009							       BSD