PM / Domains: Introduce dev_pm_domain_attach_by_name()

For the multiple PM domain case, let's introduce a new API called
dev_pm_domain_attach_by_name(). This allows a consumer driver to associate
its device with one of its PM domains, by using a name based lookup.

Do note that, currently it's only genpd that supports multiple PM domains
per device, but dev_pm_domain_attach_by_name() can easily by extended to
cover other PM domain types, if/when needed.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Rajendra Nayak <rnayak@codeaurora.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/common.c

@@ -152,6 +152,23 @@ struct device *dev_pm_domain_attach_by_id(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(dev_pm_domain_attach_by_id);
 
+/**
+ * dev_pm_domain_attach_by_name - Associate a device with one of its PM domains.
+ * @dev: The device used to lookup the PM domain.
+ * @name: The name of the PM domain.
+ *
+ * For a detailed function description, see dev_pm_domain_attach_by_id().
+ */
+struct device *dev_pm_domain_attach_by_name(struct device *dev,
+					    char *name)
+{
+	if (dev->pm_domain)
+		return ERR_PTR(-EEXIST);
+
+	return genpd_dev_pm_attach_by_name(dev, name);
+}
+EXPORT_SYMBOL_GPL(dev_pm_domain_attach_by_name);
+
 /**
  * dev_pm_domain_detach - Detach a device from its PM domain.
  * @dev: Device to detach.

include/linux/pm_domain.h

@@ -309,6 +309,8 @@ struct generic_pm_domain *of_genpd_remove_last(struct device_node *np)
 int dev_pm_domain_attach(struct device *dev, bool power_on);
 struct device *dev_pm_domain_attach_by_id(struct device *dev,
 					  unsigned int index);
+struct device *dev_pm_domain_attach_by_name(struct device *dev,
+					    char *name);
 void dev_pm_domain_detach(struct device *dev, bool power_off);
 void dev_pm_domain_set(struct device *dev, struct dev_pm_domain *pd);
 #else
@@ -321,6 +323,11 @@ static inline struct device *dev_pm_domain_attach_by_id(struct device *dev,
 {
 	return NULL;
 }
+static inline struct device *dev_pm_domain_attach_by_name(struct device *dev,
+							  char *name)
+{
+	return NULL;
+}
 static inline void dev_pm_domain_detach(struct device *dev, bool power_off) {}
 static inline void dev_pm_domain_set(struct device *dev,
 				     struct dev_pm_domain *pd) {}