attach(9E)

    int attach(dev_info_t *dip, ddi_attach_cmd_t cmd);

When power is restored to the system, each device with a reg property or with a pm-hardware-state property of value needs-suspend-resume has its attach(9E) entry point called with a command value of DDI_RESUME. If the system shutdown was aborted for some reason, each driver that was suspended is called to resume, even though the power has not been shut off. Consequently, the resume code in attach(9E) must make no assumptions about the state of the hardware; it may or may not have lost power.

The power management framework will consider the power level of the components to be unknown at DDI_RESUME time. Depending on the nature of the device, the driver writer has two choices:

• If it is possible to tell the actual power level of the components of the device without powering them up (by reading a register, for example), then the driver should notify the framework of the power level of each component by calling pm_power_has_changed(9F).

• If it is not possible to determine the power levels of the components, then the driver should mark each of them internally as unknown and be sure to call pm_raise_power(9F) before the first access to each one.

Example 9-7 shows an example of an attach(9E) routine with the DDI_RESUME command.

Example 9-7 attach(9E) Routine Implementing DDI_RESUME

int
xxattach(devinfo_t *dip, ddi_attach_cmd_t cmd)
{
        struct xxstate *xsp;
        int    instance;

        instance = ddi_get_instance(dip);
        xsp = ddi_get_soft_state(statep, instance);

        switch (cmd) {
        case DDI_ATTACH:
        ...

        case DDI_RESUME:
                mutex_enter(&xsp->mu);
                if (xsp->xx_pm_state_saved) {
                        /*
                         * Restore device register contents from
                         * xsp->xx_device_state
                         */
                        ...
                }
                /*
                 * This section is optional and only needed if the
                 * driver maintains a running timeout
                 */
                xsp->xx_timeout_id = timeout(...);

                xsp->xx_suspended = 0;          /* allow new operations */
                cv_broadcast(&xsp->xx_suspend_cv);

                /* If it is possible to determine in a device-specific way what
                 * the power levels of components are without powering the components up,
                 * then the following code is recommended
                 */
                for (i = 0; i < num_components; i++) {
                        xsp->xx_power_level[i] = xx_get_power_level(dip, i);
                        if (xsp->xx_power_level[i] != XX_LEVEL_UNKNOWN)
                                (void) pm_power_has_changed(dip, i, 
                                    xsp->xx_power_level[i]);
                }
                mutex_exit(&xsp->mu);
                return(DDI_SUCCESS);
        default:
                return(DDI_FAILURE);
        }
}

The detach(9E) and attach(9E) interfaces may also be used to resume a system that has been quiesced.