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 framework

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 autoconfiguration, 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, calling 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 structure. 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 locator 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 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.

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 compatibility 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 context, 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 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.