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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 are passed to  the  kernel.   It	contains
     various  variables to control the boot behavior of the kernel.  These vari-
     ables are typically "device hints", but can include any kernel tunable val-
     ues.

     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
     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:

	   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 uart(4) driver on the ISA
     bus:

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

     The following example disables the ACPI driver:

	   hint.acpi.0.disabled="1"

     Setting a tunable variable:

	   vm.pmap.pg_ps_enabled=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.

FreeBSD ports 15.1		November 19, 2019		 DEVICE.HINTS(5)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=device.hints&sektion=5&manpath=FreeBSD+15.1-RELEASE+and+Ports>

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