AUTOCONF(9) BSD Kernel Developer's Manual AUTOCONF(9)NAME
autoconf, config_search_loc, config_search_ia, config_found_sm_loc,
config_found_ia, config_found, config_match, config_attach_loc,
config_attach, config_attach_pseudo, config_detach, config_deactivate,
config_defer, config_interrupts, config_mountroot, config_pending_incr,
config_pending_decr, config_finalize_register — autoconfiguration frame‐
work
SYNOPSIS
#include <sys/param.h>
#include <sys/device.h>
#include <sys/errno.h>
cfdata_t
config_search_loc(cfsubmatch_t func, device_t parent, const char *ia,
const int *locs, void *aux);
cfdata_t
config_search_ia(cfsubmatch_t func, device_t parent, const char *ia,
void *aux);
device_t
config_found_sm_loc(device_t parent, const char *ia, const int *locs,
void *aux, cfprint_t print, cfsubmatch_t submatch);
device_t
config_found_ia(device_t parent, const char *ia, void *aux,
cfprint_t print);
device_t
config_found(device_t parent, void *aux, cfprint_t print);
int
config_match(device_t parent, cfdata_t cf, void *aux);
device_t
config_attach_loc(device_t parent, cfdata_t cf, const int *locs,
void *aux, cfprint_t print);
device_t
config_attach(device_t parent, cfdata_t cf, void *aux, cfprint_t print);
device_t
config_attach_pseudo(cfdata_t cf);
int
config_detach(device_t dev, int flags);
int
config_deactivate(device_t dev);
int
config_defer(device_t dev, void (*func)(device_t));
void
config_interrupts(device_t dev, void (*func)(device_t));
void
config_mountroot(device_t dev, void (*func)(device_t));
void
config_pending_incr();
void
config_pending_decr();
int
config_finalize_register(device_t dev, int (*func)(device_t));
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.
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(1). For a
description of the config(1) “device definition” language, see config(9).
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 autocon‐
figuration, giving a unique address for each instance.
FUNCTIONS
config_search_loc(func, parent, ia, locs, aux)
Performs indirect configuration of physical devices.
config_search_loc() iterates over all potential children, call‐
ing the given function func for each one. If func is NULL,
config_search_loc() applies each child's match function instead.
The argument parent is the pointer to the parent's device struc‐
ture. The argument ia is the interface attribute on which the
potential children should attach. It can be NULL, in which case
all children attaching to any attribute are considered. The
locs argument lists the locator values for the device and are
passed to function func. The given aux argument describes the
device that has been found and is simply passed on through func
to the child. config_search_loc() 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_loc() for any positive matches. If func
is NULL, then the parent should record the return value from
config_search_loc() and call config_attach_loc() 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.
config_search_ia(func, parent, ia, aux)
This function is equivalent to calling config_search_loc(func,
parent, ia, locs, aux) with locs set to NULL.
config_found_sm_loc(parent, ia, locs, aux, print, submatch)
Performs direct configuration on a physical device.
config_found_sm_loc() 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 argument ia is
the name of the interface attribute on which the child will
attach, per config(5) syntax. The argument locs lists the loca‐
tor values for the device. The given aux argument describes the
device that has been found. config_found_sm_loc() internally
uses config_search_loc(), passing on submatch, ia, locs and aux.
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 func‐
tion is called with the aux argument and, if the matches failed,
the full name (including unit number) of the parent device, oth‐
erwise NULL. The print function must return an integer value.
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.
config_found_sm_loc() 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.
config_found_ia(parent, ia, aux, print)
This function is equivalent to calling
config_found_sm_loc(parent, ia, locs, aux, print, submatch) with
locs and submatch set to NULL. It is provided for better source
code readability with locator-less device buses.
config_found(parent, aux, print)
This function is equivalent to calling
config_found_sm_loc(parent, ia, locs, aux, print, submatch) with
ia, locs and submatch set to NULL and is provided for compati‐
bility with older drivers. New code should either make the
interface attribute explicit or prefer an indirect method based
on config_search_loc().
config_match(parent, cf, aux)
Match a device. Invokes the drivers match function according to
the configuration table. The 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.
config_attach_loc(parent, locs, cf, aux, print)
Attach a found device. Allocates the memory for the softc
structure and calls the drivers attach function according to the
configuration table. If successful, config_attach_loc() returns
the softc. If unsuccessful, it returns NULL.
config_attach(parent, cf, aux, print)
This function is equivalent to calling config_attach_loc(parent,
cf, locs, aux, print) with locs set to NULL.
config_attach_pseudo(cf)
Create an instance of a pseudo-device driver. config(5) syntax
allows the creation of pseudo-devices from which regular
device_t instances can be created. Such objects are similar to
the devices that attach at the root of the device tree.
The caller is expected to allocate and fill the cfdata_t object
and pass it to config_attach_pseudo(). The content of that
object is similar to what is returned by config_search_loc() for
regular devices.
config_detach(dev, flags)
Called by the parent to detach the child device. The second
argument 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).
config_detach() returns zero if successful and an error code
otherwise. config_detach() is always called from a thread con‐
text, allowing condition variables to be used while the device
detaches itself.
config_deactivate(dev)
Called by the parent to deactivate the child device dev.
config_deactivate() is called from interrupt context to immedi‐
ately relinquish resources and notify dependent kernel subsys‐
tems that the device is about to be detached. At some later
point config_detach() will be called to finalise the removal of
the device.
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 func is called with the argument dev.
config_interrupts(dev, func)
Called by the child to defer the remainder of its configuration
until interrupts are enabled. At this point, the function func
is called with the argument dev.
config_mountroot(dev, func)
Called by the child to defer the remainder of its configuration
until the root file system is mounted. At this point, the func‐
tion func is called with the argument dev. This is used for
devices that need to load firmware image from a mounted file
system.
config_pending_incr()
Increment the config_pending semaphore. It is used to account
for deferred configurations before mounting the root file sys‐
tem.
config_pending_decr()
Decrement the config_pending semaphore. It is used to account
for deferred configurations before mounting the root file sys‐
tem.
config_finalize_register(dev, func)
Register a function to be called after all real devices have
been found.
Registered functions are all executed until all of them return
0. The callbacks should return 0 to indicate they do not
require to be called another time, but they should be aware that
they still might be in case one of them returns 1.
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 ALSOconfig(1), config(5), condvar(9), config(9), driver(9)HISTORY
Autoconfiguration first appeared in 4.1BSD. The autoconfiguration frame‐
work was completely revised in 4.4BSD. The detach and deactivate inter‐
faces appeared in NetBSD 1.5.
BSD June 26, 2010 BSD
