test

Writing Device Drivers

Callback Handler Function

Use the registered callback handling function to receive callback actions and receive arguments that are specific to each action to be processed.

typedef int (*ddi_cb_func_t)(dev_info_t *dip, ddi_cb_action_t cbaction,
                             void *cbarg, void *arg1, void *arg2);

The cbaction parameter specifies what action the driver is receiving a callback to process.

typedef enum {
        DDI_CB_INTR_ADD,
        DDI_CB_INTR_REMOVE
} ddi_cb_action_t;

A DDI_CB_INTR_ADD action means that the driver now has more interrupts available to use. A DDI_CB_INTR_REMOVE action means that the driver now has fewer interrupts available to use. Cast the cbarg parameter to an int to determine the number of interrupts added or removed. The cbarg value represents the change in the number of interrupts that are available.

For example, get the change in the number of interrupts available:

count = (int)(uintptr_t)cbarg;

If the cbaction is DDI_CB_INTR_ADD, add cbarg number of interrupt vectors. If the cbaction is DDI_CB_INTR_REMOVE, free cbarg number of interrupt vectors.

See ddi_cb_register(9F) for an explanation of arg1 and arg2.

The callback handling function must be able to perform correctly for the entire time that the function is registered. The callback function cannot depend upon any data structures that might be destroyed before the callback function is successfully unregistered.

The callback handling function must return one of the following values: