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DEVICE.HINTS(5) 	       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 will be passed to the kernel.  It	contains
     various  variables to control the boot behavior of the kernel.  These vari-
     ables are typically "device hints".

     The file contains one variable per line.  Lines starting with the `#' char-
     acter are comments and are ignored by the boot loader.

     After the file is read by the boot loader, you may examine the variables by
     the show command, and may add a  new  variable,  modify  existing	one,  or
     delete  one  by  the  set	and  unset  commands  of  the  boot  loader (see
     loader(8)).

     After the system has started, you can dump these variables by  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,
     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.
	   irq	     is the interrupt line number to be used.
	   drq	     is the DMA channel number.
	   maddr     specifies the physical memory address occupied by	the  de-
		     vice.
	   flags     sets various flag bits for the device.
	   disabled  is 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.  Consult individual device dri-
     vers' 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)

HISTORY
     The device.hints file first appeared in FreeBSD 5.0.

FreeBSD 5.0			 October 7, 2001		 DEVICE.HINTS(5)
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