PM / domains: factor out code to get the generic PM domain from a struct device

The PM domain code contains two methods to get the generic PM domain
for a struct device.  One is dev_to_genpd() which is only safe when
we know for certain that the device has a generic PM domain attached.
The other is coded into genpd_dev_pm_detach() which ensures that the
PM domain in the struct device is a generic PM domain (and so is safer).

This commit factors out the safer version, documents it, and hides the
unsafe dev_to_genpd().

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 35 insertions, 17 deletions

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 2e2e6af1f3fe..da25c0630789 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -68,7 +68,36 @@ static struct generic_pm_domain *pm_genpd_lookup_name(const char *domain_name)
         return genpd;
 }
 
-struct generic_pm_domain *dev_to_genpd(struct device *dev)
+/*
+ * Get the generic PM domain for a particular struct device.
+ * This validates the struct device pointer, the PM domain pointer,
+ * and checks that the PM domain pointer is a real generic PM domain.
+ * Any failure results in NULL being returned.
+ */
+struct generic_pm_domain *pm_genpd_lookup_dev(struct device *dev)
+{
+        struct generic_pm_domain *genpd = NULL, *gpd;
+
+        if (IS_ERR_OR_NULL(dev) || IS_ERR_OR_NULL(dev->pm_domain))
+                return NULL;
+
+        mutex_lock(&gpd_list_lock);
+        list_for_each_entry(gpd, &gpd_list, gpd_list_node) {
+                if (&gpd->domain == dev->pm_domain) {
+                        genpd = gpd;
+                        break;
+                }
+        }
+        mutex_unlock(&gpd_list_lock);
+
+        return genpd;
+}
+
+/*
+ * This should only be used where we are certain that the pm_domain
+ * attached to the device is a genpd domain.
+ */
+static struct generic_pm_domain *dev_to_genpd(struct device *dev)
 {
         if (IS_ERR_OR_NULL(dev->pm_domain))
                 return ERR_PTR(-EINVAL);
@@ -2093,21 +2122,10 @@ EXPORT_SYMBOL_GPL(of_genpd_get_from_provider);
  */
 static void genpd_dev_pm_detach(struct device *dev, bool power_off)
 {
-        struct generic_pm_domain *pd = NULL, *gpd;
+        struct generic_pm_domain *pd;
         int ret = 0;
 
-        if (!dev->pm_domain)
-                return;
-
-        mutex_lock(&gpd_list_lock);
-        list_for_each_entry(gpd, &gpd_list, gpd_list_node) {
-                if (&gpd->domain == dev->pm_domain) {
-                        pd = gpd;
-                        break;
-                }
-        }
-        mutex_unlock(&gpd_list_lock);
-
+        pd = pm_genpd_lookup_dev(dev);
         if (!pd)
                 return;
 
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 080e778118ba..681ccb053f72 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -127,7 +127,7 @@ static inline struct generic_pm_domain_data *dev_gpd_data(struct device *dev)
         return to_gpd_data(dev->power.subsys_data->domain_data);
 }
 
-extern struct generic_pm_domain *dev_to_genpd(struct device *dev);
+extern struct generic_pm_domain *pm_genpd_lookup_dev(struct device *dev);
 extern int __pm_genpd_add_device(struct generic_pm_domain *genpd,
                                  struct device *dev,
                                  struct gpd_timing_data *td);
@@ -163,9 +163,9 @@ static inline struct generic_pm_domain_data *dev_gpd_data(struct device *dev)
 {
         return ERR_PTR(-ENOSYS);
 }
-static inline struct generic_pm_domain *dev_to_genpd(struct device *dev)
+static inline struct generic_pm_domain *pm_genpd_lookup_dev(struct device *dev)
 {
-        return ERR_PTR(-ENOSYS);
+        return NULL;
 }
 static inline int __pm_genpd_add_device(struct generic_pm_domain *genpd,
                                         struct device *dev,