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AUTOCONF(9) Kernel Developer's Manual AUTOCONF(9)
NAME
autoconf, config_search, config_found, config_match, config_attach,
config_attach_pseudo, config_detach, config_detach_children,
config_deactivate, config_defer, config_interrupts, config_mountroot,
config_pending_incr, config_pending_decr, config_finalize_register -
autoconfiguration framework
SYNOPSIS
#include <sys/param.h>
#include <sys/device.h>
#include <sys/errno.h>
cfdata_t
config_search(device_t parent, void *aux, const struct cfargs *);
device_t
config_found(device_t parent, void *aux, cfprint_t print,
const struct cfargs *);
int
config_match(device_t parent, cfdata_t cf, void *aux);
int
config_probe(device_t parent, cfdata_t cf, void *aux);
device_t
config_attach(device_t parent, cfdata_t cf, void *aux, cfprint_t print,
const struct cfargs *);
device_t
config_attach_pseudo(cfdata_t cf);
int
config_detach(device_t dev, int flags);
int
config_detach_children(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
autoconfiguration, giving a unique address for each instance.
Several of the autoconfiguration functions take a strongly-typed variadic
list of arguments to pass information from driver autoconfiguration
functions to the kernel's autoconfiguration system. This list is
constructed using the CFARGS() macro, like this example:
config_search(self, NULL,
CFARGS(.search = mainbus_search,
.iattr = "mainbus"));
Each tag is followed by a tag-specific value.
submatch A pointer to a `submatch' function used in direct
configuration.
search A pointer to a `search' function used in indirect
configuration.
iattr A pointer to a constant C string (const char *)
specifying an interface attribute. If a parent
device carries only a single interface attribute,
then this argument may be omitted. If an interface
attribute is specified that the parent device does
not carry, or no interface attribute is specified
and the parent device carries more than one,
behavior is undefined. On kernels built with the
DIAGNOSTIC option, this may result in an assertion
panic.
locators A pointer to a constant array of integers (const int
*) containing interface attribute-specific locators.
devhandle A devhandle_t (passed by value) corresponding to the
device being attached.
If no arguments are to be passed, the special value CFARGS_NONE may be
used in place of the CFARGS() macro.
FUNCTIONS
config_search(parent, aux, cfargs)
Cfargs consumed: search, iattr, locators.
Performs indirect configuration of physical devices.
config_search() iterates over all potential children, calling
the given search function If no search function is specified,
applies the potential child's match function instead. The
argument parent is the pointer to the parent's device
structure. If an interface attribute is specified, only
potential children eligible to attach to that interface
attribute will be consulted. If specified, the locators
argument lists the locator values for the device and are
passed to the search function. The given aux argument
describes the device that has been found and is simply passed
on through the search function to the child. config_search()
returns a pointer to the configuration data that indicates
the best-matched child or NULL otherwise.
The role of the search function is to call config_probe() for
each potential child and call config_attach() for any
positive matches. If no search function is specified, 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(parent, aux, print, cfargs)
Cfargs consumed: submatch, iattr, locators, devhandle.
Performs direct configuration on a physical device.
config_found() is called by the parent and in turn calls the
specified submatch function as determined by the
configuration table. The submatch function compares user-
specified locators from the machine description file against
those specifying a found device, calling config_match() if
they match (including wildcard matching). If a submatch
function is not specified, then driver match functions are
called directly. The argument parent is the pointer to the
parent's device structure. If an interface attribute is
specified, only potential children eligible to attach to that
interface attribute will be consulted. If specified, the
locators argument lists the locator values for the found
device and may be used by the submatch function and will be
recorded in the device structure of the child device. The
given aux argument describes the device that has been found.
config_found() internally uses config_search(). 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. 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. If a device handle
is specified, that handle will be associated with the
resulting child device structure if a driver matches.
config_found() returns a pointer to the attached device's
device structure if the device is attached, NULL otherwise.
Most callers can ignore this value, since the system will
already have printed a diagnostic.
config_match(parent, cf, aux)
Match a device (direct configuration). Invokes the driver's
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_probe(parent, cf, aux)
Probe for a device (indirect configuration). Invokes the
driver's match function according to the configuration table.
The config_probe() function returns a nonzero integer to
indicate a successful probe and a value of 0 otherwise.
Unlike config_match(), the return value of config_probe() is
not intended to reflect a confidence value.
config_attach(parent, cf, aux, print, cfargs)
Cfargs consumed: locators, devhandle.
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 a pointer to the device structure. If unsuccessful,
it returns 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()
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
context, allowing condition variables to be used while the
device detaches itself.
config_detach_children(dev, flags)
Iterate through all attached devices, calling config_detach()
for each child of dev, passing flags. If detaching any child
results in an error, the iteration will halt and any
remaining devices will not be detached.
config_detach_children() returns zero if successful and an
error code otherwise.
config_deactivate(dev)
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.
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 function 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 system.
config_pending_decr()
Decrement the config_pending semaphore. It is used to
account for deferred configurations before mounting the root
file system.
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 ALSO
config(1), config(5), condvar(9), config(9), driver(9)
HISTORY
Autoconfiguration first appeared in 4.1BSD. The autoconfiguration
framework was completely revised in 4.4BSD. The detach and deactivate
interfaces appeared in NetBSD 1.5.
NetBSD 10.99 August 7, 2021 NetBSD 10.99