PM: runtime: Allow unassigned ->runtime_suspend|resume callbacks

We are currently allowing ->runtime_idle() callbacks to be unassigned
without returning an error code from rpm_idle(). This has been useful to
avoid boilerplate code in drivers. Let's take this approach a step further,
by allowing also unassigned ->runtime_suspend|resume() callbacks.

In this way, a consumer/supplier device link can be used to let a consumer
device be power managed through its supplier device, without requiring
assigned ->runtime_suspend|resume() callbacks for the consumer device, for
example.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 68bebbf81347f55f09f4b1870307ec9d5062e9b7..8a66eaf731e4888354d8aeb61ae3dcc4b9ae74b4 100644 (file)
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -345,7 +345,7 @@ static void rpm_suspend_suppliers(struct device *dev)
 static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
        __releases(&dev->power.lock) __acquires(&dev->power.lock)
 {
-       int retval, idx;
+       int retval = 0, idx;
        bool use_links = dev->power.links_count > 0;
 
        if (dev->power.irq_safe) {
@@ -373,7 +373,8 @@ static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
                }
        }
 
-       retval = cb(dev);
+       if (cb)
+               retval = cb(dev);
 
        if (dev->power.irq_safe) {
                spin_lock(&dev->power.lock);
@@ -484,9 +485,6 @@ static int rpm_callback(int (*cb)(struct device *), struct device *dev)
 {
        int retval;
 
-       if (!cb)
-               return -ENOSYS;
-
        if (dev->power.memalloc_noio) {
                unsigned int noio_flag;