xref: /freebsd/share/man/man5/device.hints.5 (revision 3fcd5f6c3013080a388325cbca13e75b8b5da09c)

.\"
.\" Copyright (c) 2001
.\" Kazutaka YOKOTA <yokota@zodiac.mech.utsunomiya-u.ac.jp>
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.Dd October 7, 2001
.Dt DEVICE.HINTS 5
.Os
.Sh NAME
.Nm device.hints
.Nd device resource hints
.Sh DESCRIPTION
The
.Pa /boot/device.hints
file is read in by the boot
.Xr 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 variables are typically
.Dq device hints .
.\" .Dq device hints ,
.\" and other control variables.
.Pp
The file contain one variable per line.
Lines starting with
.Li #
are comments and are ignore by the boot loader.
.Pp
After the file is read by the boot loader, you may examine
the variables by the
.Ic show
command, and may add a new variable, modify existing one,
or delete one by the
.Ic set
and
.Ic unset
commands of the boot loader
.Po
see
.Xr loader 8
.Pc .
.Pp
After the system has started, you can dump these variables
by the
.Xr kenv 1
command.
.Sh 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.
.Pp
A device hint line looks like:
.Pp
.Dl hint.<driver>.<unit>.<keyword>="<value>"
.Pp
where
.Ar <driver>
is the name of a device driver,
.Ar <unit>
is the unit number,
.Ar <keyword>
is the keyword of the hint.
The keyword may be:
.Pp
.Bl -tag -width "disabledXXX" -compact -offset indent
.It at
specifies a bus to which the device is attached.
.It port
specifies the start address of I/O ports to be used by the device.
.It irq
is the interrupt line number to be used.
.It drq
is the DMA channel number.
.It maddr
specifies the physical memory address occupied by the device.
.It flags
sets various flag bits for the device.
.It disabled
is set to
.Qq 1
to disable the device.
.El
.Pp
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.
.\" .Sh CONTROL VARIABLES
.\" Lines not starting with
.\" .Dq hint.
.\" specify other control variables for the kernel.
.\" They look:
.\" .Pp
.\" .Dl <name>="<value>"
.\" XXX
.\" WE SHOULD LIST AVAILABLE VARIABLE NAMES AND THEIR POSSIBLE VALUES HERE!
.\" .Pp
.Sh FILES
.Bl -tag -width /sys/<arch>/conf/GENERIC.hintsXXX -compact
.It Pa /boot/device.hints
Device resource hint file.
.It Pa /sys/<arch>/conf/GENERIC.hints
Sample resource hints for the GENERIC kernel.
.It Pa /sys/<arch>/conf/NOTES
Notes on the kernel configuration file and device resource hints.
.El
.Sh EXAMPLES
The following example sets up resources for the
.Xr sio 4
driver on the ISA bus.
.Pp
.Bd -literal -offset indent
hint.sio.0.at="isa"
hint.sio.0.port="0x3f8"
hint.sio.0.flags="0x10"
hint.sio.0.irq="4"
.Ed
.\" .Pp
.\" A control variable may look like:
.\" .Pp
.\" .Bd -literal -offset indent
.\" debug.acpi.layer="ACPI_RESOURCES"
.\" .Ed
.Sh SEE ALSO
.Xr kenv 1 ,
.Xr loader.conf 5 ,
.Xr loader 8
.Sh HISTORY
The
.Nm
file first appeared in
.Fx 5.0 .