NAME
autoconf —
autoconfiguration framework
SYNOPSIS
#include
<sys/param.h>
#include <sys/device.h>
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.
The autoconfiguration framework supports direct configuration where the bus driver can determine the devices present.
The autoconfiguration framework also supports 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.
The autoconfiguration process occurs at system bootstrap and is driven by a table generated from a “machine description” file by config(8). For a description of the config(8) “device definition” language, see files.conf(5).
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.
INDIRECT CONFIGURATION
void *
config_search(cfmatch_t
func, struct device
*parent, void
*aux);
void *
config_rootsearch(cfmatch_t
func, char
*rootname, void
*aux);
The
config_search()
function performs indirect configuration of physical devices by iterating
over all potential children, calling the given function
func for each one.
The
config_rootsearch()
function finds the root device identified by the string
rootname, in a manner similar to
config_search(), except that there is no parent
device. If func is NULL,
config_search() applies each child's match function
instead. The argument parent is the pointer to the
parent's device structure. The given aux argument
describes the device that has been found and is simply passed on through
func to the child.
config_search() returns a pointer to the
best-matched child or NULL otherwise.
The role of func is to
call the match function for each device and call
config_attach()
for any positive matches.
typedef int (*cfmatch_t)(struct device *parent, void *child, void *aux);
If func is
NULL, then the parent should record the return value
from
config_search()
and call config_attach() itself.
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.
DIRECT CONFIGURATION
struct device *
config_found_sm(struct
device *parent, void
*aux, cfprint_t
print, cfmatch_t
submatch);
struct device *
config_found(struct
device *parent, void
*aux, cfprint_t
print);
struct device *
config_rootfound(char
*rootname, void
*aux);
The
config_found_sm()
function performs direct configuration on a physical device.
config_found_sm() is called by the parent and in
turn calls the submatch function to call the match
function as determined by the configuration table. If
submatch is NULL, the driver
match functions are called directly. The argument
parent is the pointer to the parent's device
structure. The given aux argument describes the device
that has been found. The 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 print function
to produce additional information if desired. If no driver takes a match,
the same print function is called to complain. The
print function is called with the aux argument and, if
the matches failed, the full name (including unit number) of the parent
device, otherwise NULL.
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" */
Two special strings, “not configured” and
“unsupported” 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.
The
config_found_sm()
function returns a pointer to the attached device's softc
structure if the device is attached, NULL otherwise.
Most callers can ignore this value, since the system will already have
printed a diagnostic.
The
config_found()
macro expands to
config_found_sm(parent,
aux, print,
submatch) with submatch set to
NULL and is provided for compatibility with older
drivers.
The
config_rootfound()
function performs the same operation on the root device identified by the
rootname string.
DEFERRED CONFIGURATION
void
config_defer(struct
device *dev, void
(*func)(struct device *));
The
config_defer()
function is 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 func is called with the argument
dev.
CODE REFERENCES
The autoconfiguration framework itself is implemented within the file sys/kern/subr_autoconf.c. Data structures and function prototypes for the framework are located in sys/sys/device.h.
SEE ALSO
HISTORY
Autoconfiguration first appeared in 4.1BSD. The autoconfiguration framework was completely revised in 4.4BSD.