.\"     $NetBSD: autoconf.9,v 1.13 2002/10/14 13:43:15 wiz Exp $
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.\" by Gregory McGarry.
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.Dd October 5, 2002
.Dt AUTOCONF 9
.Os
.Sh NAME
.Nm autoconf ,
.Nm config_search ,
.Nm config_found_sm ,
.Nm config_found ,
.Nm config_match ,
.Nm config_attach ,
.Nm config_detach ,
.Nm config_activate ,
.Nm config_deactivate ,
.Nm config_defer ,
.Nm config_interrupts ,
.Nm config_pending_incr ,
.Nm config_pending_decr
.Nd autoconfiguration framework
.Sh SYNOPSIS
.Fd #include \*[Lt]sys/param.h\*[Gt]
.Fd #include \*[Lt]sys/device.h\*[Gt]
.Fd #include \*[Lt]sys/error.h\*[Gt]
.Ft struct cfdata *
.Fn config_search "cfmatch_t func" "struct device *parent" "void *aux"
.Ft struct device *
.Fn config_found_sm "struct device *parent" "void *aux" "cfprint_t print" \
"cfmatch_t submatch"
.Ft struct device *
.Fn config_found "struct device *parent" "void *aux" "cfprint_t print"
.Ft int
.Fn config_match "struct device *parent" "struct cfdata *cf" "void *aux"
.Ft struct device *
.Fn config_attach "struct device *parent" "struct cfdata *cf" "void *aux" \
"cfprint_t print"
.Ft int
.Fn config_detach "struct device *dev" "int flags"
.Ft int
.Fn config_activate "struct device *dev"
.Ft int
.Fn config_deactivate "struct device *dev"
.Ft int
.Fn config_defer "struct device *dev" "void (*func)(struct device *)"
.Ft void
.Fn config_interrupts "struct device *dev" "void (*func)(struct device *)"
.Ft void
.Fn config_pending_incr
.Ft void
.Fn config_pending_decr
.Sh DESCRIPTION
Autoconfiguration is the process of matching hardware devices with an
appropriate device driver.
In its most basic form, autoconfiguration consists of the recursive process
of finding and attaching all devices on a bus, including other busses.
.Pp
The autoconfiguration framework supports
.Em direct configuration
where the bus driver can determine the devices present.
The autoconfiguration framework also supports
.Em indirect configuration
where the drivers must probe the bus looking for the presence of a device.
Direct configuration is preferred since it can find hardware
regardless of the presence of proper drivers.
.Pp
The autoconfiguration process occurs at system bootstrap and is driven
by a table generated from a
.Do
machine description
.Dc
file by
.Xr config 8 .
For a description of the
.Xr config 8
.Do
device definition
.Dc
language, see
.Xr config 9 .
.Pp
Each device must have a name consisting of an alphanumeric string that
ends with a unit number.
The unit number identifies an instance of the driver.
Device data structures are allocated dynamically during
autoconfiguration, giving a unique address for each instance.
.Sh FUNCTIONS
.Bl -tag -width compact
.It Fn config_search "func" "parent" "aux"
Performs indirect configuration of physical devices.
.Fn config_search
iterates over all potential children, calling the given
function
.Fa func
for each one.
If
.Fa func
is
.Dv NULL ,
.Fn config_search
applies each child's match function instead.
The argument
.Fa parent
is the pointer to the parent's device structure.
The given
.Fa aux
argument describes the device that has been found and is simply passed
on through
.Fa func
to the child.
.Fn config_search
returns a pointer to the best-matched child or
.Dv NULL
otherwise.
.Pp
The role of
.Fa func
is to call
the match function for each device and call
.Fn config_attach
for any positive matches.
If
.Fa func
is
.Dv NULL ,
then the parent should record the return value from
.Fn config_search
and call
.Fn config_attach
itself.
.Pp
Note that this function is designed so that it can be used to apply an
arbitrary function to all potential children.
In this case callers may choose to ignore the return value.
.It Fn config_found_sm "parent" "aux" "print" "submatch"
Performs direct configuration on a physical device.
.Fn config_found_sm
is called by the parent and in turn calls the
.Fa submatch
function to call the match function as
determined by the configuration table.
If
.Fa submatch
is
.Dv NULL ,
the driver match functions are called directly.
The argument
.Fa parent
is the pointer to the parent's device structure.
The given
.Fa aux
argument describes the device that has been found.
The
.Em softc
structure for the matched device will be allocated, and the
appropriate driver attach function will be called.
If the device is matched, the system prints the name of the child and
parent devices, and then calls the
.Fa print
function to produce additional information if desired.
If no driver takes a match, the same
.Fa print
function is called to complain.
The print function is called with the
.Fa aux
argument and, if the matches failed, the full name (including unit
number) of the parent device, otherwise
.Dv NULL .
The
.Fa print
function must return an integer value.
.Pp
Two special strings,
.Do
not configured
.Dc
and
.Do
unsupported
.Dc
will be appended automatically to non-driver reports if the return
value is UNCONF or UNSUPP respectively; otherwise the function should
return the value QUIET.
.Pp
.Fn config_found_sm
returns a pointer to the attached device's
.Em softc
structure if the device is attached,
.Dv NULL
otherwise.
Most callers can ignore this value, since the system will already have
printed a diagnostic.
.It Fn config_found "parent" "aux" "print"
This function is equivalent to calling
.Fn config_found_sm "parent" "aux" "print" "submatch"
with
.Fa submatch
set to
.Dv NULL
and is provided for compatibility with older drivers.
.It Fn config_match "parent" "cf" "aux"
Match a device.
Invokes the drivers match function according to the
configuration table.
The
.Fn config_match
function returns a nonzero integer indicating the confidence of
supporting this device and a value of 0 if the driver doesn't support
the device.
.It Fn config_attach "parent" "cf" "aux" "print"
Attach a found device.
Allocates the memory for the
.Em softc
structure and calls the drivers attach function according to the
configuration table.
If successful,
.Fn config_attach
returns the
.Em softc .
If unsuccessful, it returns
.Dv NULL .
.It Fn config_detach "dev" "flags"
Called by the parent to detach the child device.
The second argument
.Em flags
contains detachment flags.
Valid values are DETACH_FORCE (force detachment (e.g., because of hardware
removal)) and DETACH_QUIET (do not print a notice).
.Fn config_detach
returns zero if successful and an error code otherwise.
.Fn config_detach
is always called from a thread context, allowing
.Xr sleep 9
to be called while the device detaches itself.
.It Fn config_activate "dev"
Called by the parent to activate the child device
.Fa dev .
It is called to activate resources and initialise other kernel
subsystems (such as the network subsystem).
.Fn config_activate
is called from interrupt context after the device has been attached.
.It Fn config_deactivate "dev"
Called by the parent to deactivate the child device
.Fa dev .
.Fn config_deactivate
is called from interrupt context to immediately relinquish resources
and notify dependent kernel subsystems that the device is about to be
detached.
At some later point
.Fn config_detach
will be called to finalise the removal of the device.
.It Fn config_defer "dev" "func"
Called by the child to defer the remainder of its configuration until
all its parent's devices have been attached.
At this point, the function
.Fa func
is called with the argument
.Fa dev .
.It Fn config_interrupts "struct device *dev" "void (*func)(struct device *)"
Called by the child to defer the remainder of its configuration until
interrupts are enabled.
At this point, the function
.Fa func
is called with the argument
.Fa dev .
.It Fn config_pending_incr
Increment the
.Va config_pending
semaphore.
It is used to account for deferred configurations before
mounting the root file system.
.It Fn config_pending_decr
Decrement the
.Va config_pending
semaphore.
It is used to account for deferred configurations before
mounting the root file system.
.El
.Sh CODE REFERENCES
This section describes places within the
.Nx
source tree where actual code implementing or utilising the
autoconfiguration framework can be found.
All pathnames are relative to
.Pa /usr/src .
.Pp
The autoconfiguration framework itself is implemented within the file
.Pa sys/kern/subr_autoconf.c .
Data structures and function prototypes for the framework are located in
.Pa sys/sys/device.h .
.Sh SEE ALSO
.Xr config 8 ,
.Xr config 9 ,
.Xr driver 9
.Sh HISTORY
Autoconfiguration first appeared in
.Bx 4.1 .
The autoconfiguration framework was completely revised in
.Bx 4.4 .
The detach and activate/deactivate interfaces appeared in
.Nx 1.5 .