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

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 buses.

The autoconfiguration framework supports where the bus driver can determine the devices present.

The autoconfiguration framework also supports 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
(void);

The () function initializes the autoconfiguration data structures.

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

void *
config_rootsearch(cfmatch_t func, char *rootname, void *aux);

The () 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 best-matched child or NULL otherwise.

The role of func is to call the match function for each device and call () 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 () 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 *
(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 () 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 () 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 () macro expands to config_found_sm(parent, aux, print, submatch) with submatch set to NULL and is provided for compatibility with older drivers.

The () 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);

int
config_detach(struct device *dev, int flags);

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

int
config_activate(struct device *dev);

int
config_deactivate(struct device *dev);

The () 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 () 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.

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

The () 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.

June 4, 2013 OpenBSD-5.4