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.Dd $Mdocdate: April 18 2018 $
.Dt CONFIG_SEARCH 9
.Os
.Sh NAME
.Nm config_search ,
.Nm config_rootsearch ,
.Nm config_found_sm ,
.Nm config_found ,
.Nm config_rootfound
.Nd autoconfiguration framework
.Sh SYNOPSIS
.In sys/param.h
.In sys/device.h
.Ft "void *"
.Fn config_search "cfmatch_t func" "struct device *parent" "void *aux"
.Ft "void *"
.Fn config_rootsearch "cfmatch_t func" "char *rootname" "void *aux"
.Ft "struct device *"
.Fo config_found_sm
.Fa "struct device *parent"
.Fa "void *aux"
.Fa "cfprint_t print"
.Fa "cfmatch_t submatch"
.Fc
.Ft "struct device *"
.Fn config_found "struct device *parent" "void *aux" "cfprint_t print"
.Ft "struct device *"
.Fn config_rootfound "char *rootname" "void *aux"
.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 buses.
.Pp
The autoconfiguration framework supports
.Em direct configuration
where the bus driver can determine the devices present.
.Pp
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 files.conf 5 .
.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.
.Ss Indirect Configuration
The
.Fn config_search
function performs indirect configuration of physical devices by iterating
over all potential children, calling the given function
.Fa func
for each one.
.Pp
The
.Fn config_rootsearch
function finds the root device identified by the string
.Fa rootname ,
in a manner similar to
.Fn config_search ,
except that there is no parent device.
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.
.Bd -literal
typedef int (*cfmatch_t)(struct device *parent, void *child, void *aux);
.Ed
.Pp
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.
.Ss Direct Configuration
The
.Fn config_found_sm
function 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.
.Pp
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 .
.Bd -literal
typedef int (*cfprint_t)(void *aux, const char *parentname);
#define	QUIET	0		/* print nothing */
#define	UNCONF	1		/* print " not configured" */
#define	UNSUPP	2		/* print " not supported" */
.Ed
.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
.Dv UNCONF
or
.Dv UNSUPP
respectively, otherwise the function should return the value
.Dv QUIET .
.Pp
The
.Fn config_found_sm
function 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.
.Pp
The
.Fn config_found
macro expands to
.Fn config_found_sm "parent" "aux" "print" "submatch"
with
.Fa submatch
set to
.Dv NULL
and is provided for compatibility with older drivers.
.Pp
The
.Fn config_rootfound
function performs the same operation on the root device identified
by the
.Fa rootname
string.
.Sh CODE REFERENCES
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 autoconf 4 ,
.Xr files.conf 5 ,
.Xr config 8 ,
.Xr config_attach 9
.Sh HISTORY
Autoconfiguration first appeared in
.Bx 4.1 .
The autoconfiguration framework was completely revised in
.Bx 4.4 .