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AUTOCONF(9)              BSD Kernel Developer's Manual             AUTOCONF(9)

     autoconf, config_search, config_found_sm, config_found, config_match,
     config_attach, config_detach, config_activate, config_deactivate,
     config_defer, config_interrupts, config_pending_incr, config_pending_decr
     -- autoconfiguration framework

     #include <&lt;sys/param.h>&gt;
     #include <&lt;sys/device.h>&gt;
     #include <&lt;sys/errno.h>&gt;

     struct cfdata *
     config_search(cfmatch_t func, struct device *parent, void *aux);

     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);

     config_match(struct device *parent, struct cfdata *cf, void *aux);

     struct device *
     config_attach(struct device *parent, struct cfdata *cf, void *aux,
         cfprint_t print);

     config_detach(struct device *dev, int flags);

     config_activate(struct device *dev);

     config_deactivate(struct device *dev);

     config_defer(struct device *dev, void (*func)(struct device *));

     config_interrupts(struct device *dev, void (*func)(struct device *));



     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(8).  For
     a description of the config(8) ``device definition'' language, see

     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.

     config_search(func, parent, aux)
              Performs indirect configuration of physical devices.
              config_search() iterates over all potential children, calling
              the given function func for each one.  If func is NULL,
              config_search() applies each child's match function instead.
              The argument parent is the pointer to the parent's device struc-
              ture.  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.  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.

     config_found_sm(parent, aux, print, submatch)
              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 argu-
              ment describes the device that has been found.  The softc struc-
              ture for the matched device will be allocated, and the appropri-
              ate 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, other-
              wise 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() 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(parent, aux, print)
              This function is equivalent to calling config_found_sm(parent,
              aux, print, submatch) with submatch set to NULL and is provided
              for compatibility with older drivers.

     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

     config_attach(parent, 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() returns the
              softc.  If unsuccessful, it returns NULL.

     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 ltsleep(9) to be called while the device detaches

              Called by the parent to activate the child device dev.  It is
              called to activate resources and initialise other kernel subsys-
              tems (such as the network subsystem).  config_activate() is
              called from interrupt context after the device has been

              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(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 func
              is called with the argument dev.

              Increment the config_pending semaphore.  It is used to account
              for deferred configurations before mounting the root file sys-

              Decrement the config_pending semaphore.  It is used to account
              for deferred configurations before mounting the root file sys-

     This section describes places within the NetBSD source tree where actual
     code implementing or using the autoconfiguration framework can be found.
     All pathnames are relative to /usr/src.

     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.

     config(8), config(9), driver(9)

     Autoconfiguration first appeared in 4.1BSD.  The autoconfiguration frame-
     work was completely revised in 4.4BSD.  The detach and activate/deacti-
     vate interfaces appeared in NetBSD 1.5.

BSD                             October 5, 2002                            BSD