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NAME    [Toc]    [Back]

     autoconf - autoconfiguration framework

SYNOPSIS    [Toc]    [Back]

     #include <sys/param.h>
     #include <sys/device.h>

DESCRIPTION    [Toc]    [Back]

     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
     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 autoconfiguration,
 giving a unique address for each instance.

INITIALIZATION    [Toc]    [Back]


     The config_init() function initializes the autoconfiguration
data structures.


     void *
     config_search(cfmatch_t func, struct  device  *parent,  void

     void *
     config_rootsearch(cfmatch_t   func,   char  *rootname,  void

     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  bestmatched 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.


     struct device *
     config_found_sm(struct device *parent, void *aux,  cfprint_t
             cfmatch_t submatch);

     struct device *
     config_found(struct  device  *parent,  void  *aux, cfprint_t

     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

     If the device is matched, the system prints the name of  the
child and
     parent devices, and then calls the print function to produce
     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

     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.


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

     config_detach(struct device *dev, int flags);

     The config_attach() function attaches a found device.  Memory is allocated
 for the softc structure and the driver's attach  function
is called according
   to   the   configuration  table.   If  successful,
config_attach() returns
 the softc.  If unsuccessful, it returns NULL.

     The config_detach() function is called by the parent to  detach the child
     device.   The  second  argument  flags  contains  detachment

     #define DETACH_FORCE    0x01    /* Force  detachment;  hardware gone */
     #define DETACH_QUIET    0x02    /* Don't print a notice */

     The  config_detach() function returns zero if successful and
an error code
     otherwise.  config_detach() is always  called  from  process
context, allowing
  sleep(9)  to be called while the device detaches itself
(to deal with
     processes which have a device open).

     config_activate(struct device *dev);

     config_deactivate(struct device *dev);

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

     The config_deactivate() function is called by the parent  to
     the  child  device  dev.  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,
     config_detach() will be called to finalise  the  removal  of
the device.


     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

CODE REFERENCES    [Toc]    [Back]

     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    [Toc]    [Back]

     autoconf(4), files.conf(5), config(8)

HISTORY    [Toc]    [Back]

     Autoconfiguration first appeared in 4.1BSD.  The autoconfiguration framework
 was completely revised in 4.4BSD.  The detach and activate/deactivate
 interfaces appeared in NetBSD 1.5.

OpenBSD      3.6                          August     25,     2002
[ Back ]
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