kern_control.h

Introduction

This header defines an API to communicate between a kernel extension and a process outside of the kernel.

Structs and Unions

struct ctl_event_data { 
    u_int32_t ctl_id; /* Kernel Controller ID */
    u_int32_t ctl_unit; 
};  

Fields

ctl_id

The kernel control id.

ctl_unit

The kernel control unit.

Discussion

This structure is used for KEV_CTL_SUBCLASS kernel events.

struct ctl_info { 
    u_int32_t ctl_id; /* Kernel Controller ID */
    char ctl_name[96  ]; /* Kernel Controller Name (a C string) */
};  

Fields

ctl_id

The kernel control id, filled out upon return.

ctl_name

The kernel control name to find.

Discussion

This structure is used with the CTLIOCGINFO ioctl to translate from a kernel control name to a control id.

struct sockaddr_ctl { 
    u_char sc_len; /* depends on size of bundle ID string */
    u_char sc_family; /* AF_SYSTEM */
    u_int16_t ss_sysaddr; /* AF_SYS_KERNCONTROL */
    u_int32_t sc_id; /* Controller unique identifier */
    u_int32_t sc_unit; /* Developer private unit number */
    u_int32_t sc_reserved[5]; 
};  

Fields

sc_len

The length of the structure.

sc_family

AF_SYSTEM.

ss_sysaddr

AF_SYS_KERNCONTROL.

sc_id

Controller unique identifier.

sc_unit

Kernel controller private unit number.

sc_reserved

Reserved, must be set to zero.

Discussion

The controller address structure is used to establish contact between a user client and a kernel controller. The sc_id/sc_unit uniquely identify each controller. sc_id is a unique identifier assigned to the controller. The identifier can be assigned by the system at registration time or be a 32-bit creator code obtained from Apple Computer. sc_unit is a unit number for this sc_id, and is privately used by the kernel controller to identify several instances of the controller.

#defines

#define CTLIOCGCOUNT _IOR(
    'N', 2, int) /* get number of control structures registered */

Discussion

The CTLIOCGCOUNT ioctl can be used to determine the number of kernel controllers registered.

#define CTLIOCGINFO _IOWR(
    'N', 3, struct ctl_info) /* get id from name */

Discussion

The CTLIOCGINFO ioctl can be used to convert a kernel control name to a kernel control id.

#define KEV_CTL_DEREGISTERED 2 /* a controller disappears */

Discussion

The event code indicating a controller was unregistered. The data portion will contain a ctl_event_data.

#define KEV_CTL_REGISTERED 1 /* a new controller appears */

Discussion

The event code indicating a new controller was registered. The data portion will contain a ctl_event_data.

#define KEV_CTL_SUBCLASS 2 

Discussion

The kernel event subclass for kernel control events.

#define MAX_KCTL_NAME 96 

Discussion

Kernel control names must be no longer than MAX_KCTL_NAME.