man pages section 9: DDI and DKI Kernel Functions

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Updated: July 2014



ldi_add_event_handler - add NDI event service callback handler


#include <sys/ddi_obsolete.h>

int ldi_add_event_handler(ldi_handle_t lh, ddi_eventcookie_t ec, 
     void (*handler)(ldi_handle_t, ddi_eventcookie_t,
     void *, void *) void *arg, ldi_callback_id_t *id);

Interface Level



ldi_handle_t lh

Layered handle representing event notification device.

ddi_eventcookie_t ec

Cookie returned from call to ldi_get_eventcookie(9F).

void (*handler)(ldi_handle_t, ddi_eventcookie_t, void *, void *)

Callback handler for NDI event service notification.

void *arg

Pointer to opaque data supplied by caller. Typically, this is a pointer to the layered driver's softstate structure.

ldi_callback_id_t *id

Pointer to registration id, where a unique registration id is returned. Registration id must be saved and used when calling ldi_remove_event_handler(9F) to unregister a callback handler.


This function is obsolete and is only maintained for compatibility. Use of this function is strongly discouraged. For equivalent functionality provided by new interfaces, see ldi_ev_get_cookie(9F) and ldi_ev_register_callbacks(9F).

The ldi_add_event_handler() function adds a callback handler to be invoked at the occurance of the event specified by the cookie. Adding a callback handler is also known as subscribing to an event. Upon successful subscription, the handler is invoked when the event occurs. You can unregister the handler by using ldi_remove_event_handler(9F).

An instance of a layered driver can register multiple handlers for an event or a single handler for multiple events. Callback order is not defined and should be assumed to be random.

The routine handler is invoked with the following arguments:

ldi_handle_t lh

Layered handle representing the device for which the event notification is requested.

ddi_eventcookie_t ec

Structure describing event that occurred.

void *arg

Opaque data pointer provided by the driver during callback registration.

void *impl_data

Pointer to event specific data defined by the framework that invokes the callback function.

Return Values


Callback handler registered successfully.


Failed to register callback handler. Possible reasons include lack of resources or a bad cookie.


The ldi_add_event_handler() function can be called from user and kernel contexts only.

See also

ldi_ev_get_cookie(9F), ldi_ev_register_callbacks(9F), ldi_get_eventcookie(9F), ldi_remove_event_handler(9F)

Writing Device Drivers


Layered drivers must remove all registered callback handlers for a device instance, represented by the layered handle, by calling ldi_remove_event_handler(9F) before the layered driver's detach(9E) routine completes.