autoconf - autoconfiguration framework
#include <sys/param.h>
#include <sys/device.h>
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
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.
void
config_init(void);
The config_init() function initializes the autoconfiguration
data structures.
INDIRECT CONFIGURATION [Toc] [Back] 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 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
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.
ATTACHING AND DETACHING DEVICES [Toc] [Back] struct device *
config_attach(struct device *parent, void *cf, void *aux,
cfprint_t print);
int
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
flags:
#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).
DEVICE ACTIVATION/DEACTIVATION
int
config_activate(struct device *dev);
int
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).
config_activate()
is called from interrupt context after the device has been
attached.
The config_deactivate() function is called by the parent to
deactivate
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.
DEFERRED CONFIGURATION [Toc] [Back] 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.
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.
autoconf(4), files.conf(5), config(8)
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
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