PM driver callbacks helper

callback.c

// Using the && (logical AND) operator.

#define pm_driver_has_callback(__device, __callback) \
        ((__device)->driver && (__device)->driver->pm && (__device)->driver->pm->__callback)

#define pm_driver_do_callback(__device, __callback) \
        (pm_driver_has_callback(__device, __callback) ? (__device)->driver->pm->__callback(__device) : 0)

// Using a statement expression to avoid using ternary operator...

#define pm_driver_has_callback(__device, __callback) \
({ \
    int __result = -EINVAL; \
    if ((__device)->driver && (__device)->driver->pm && (__device)->driver->pm->__callback) \
        __result = 0; \
    __result; \
})

#define pm_driver_do_callback(__device, __callback) \
({ \
    int __result = -EINVAL; \
    if (pm_driver_has_callback(__device, __callback)) \
        __result = (__device)->driver->pm->__callback(__device); \
    __result; \
})

patch.diff

 static int gb_bundle_suspend(struct device *dev)
 {
 	struct gb_bundle *bundle = to_gb_bundle(dev);
-	const struct dev_pm_ops *pm = dev->driver->pm;
 	int ret;

-	if (pm && pm->runtime_suspend) {
-		ret = pm->runtime_suspend(&bundle->dev);
+	if (pm_driver_has_callback(dev, runtime_suspend)) {
+		ret = pm_driver_do_callback(&bundle->dev, runtime_suspend);
 		if (ret)
 			return ret;
 	} else {
@@ -121,8 +142,8 @@ static int gb_bundle_suspend(struct device *dev)

 	ret = gb_control_bundle_suspend(bundle->intf->control, bundle->id);
 	if (ret) {
-		if (pm && pm->runtime_resume)
-			ret = pm->runtime_resume(dev);
+		if (pm_driver_has_callback(dev, runtime_resume))
+			ret = pm_driver_do_callback(dev, runtime_resume);
 		else
 			gb_bundle_enable_all_connections(bundle);