[PATCH v3 3/9] PM / Domains: Add APIs to attach/detach a PM domain for a device

To maintain scalability let's add common methods to attach and detach
a PM domain for a device, dev_pm_domain_attach|detach().

Typically dev_pm_domain_attach() shall be invoked from subsystem level
code at the probe phase to try to attach a device to its PM domain.
The reversed actions may be done a the remove phase and then by invoking
dev_pm_domain_detach().

The supported PM domains at this point are the ACPI and the generic
PM domains.

Signed-off-by: Ulf Hansson <redacted>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
---
 drivers/base/power/common.c | 56 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/pm.h          | 14 ++++++++++++
 2 files changed, 70 insertions(+)

diff --git a/drivers/base/power/common.c b/drivers/base/power/common.c
index df2e5ee..9a86b16 100644
--- a/drivers/base/power/common.c
+++ b/drivers/base/power/common.c

@@ -11,6 +11,8 @@
 #include <linux/export.h>
 #include <linux/slab.h>
 #include <linux/pm_clock.h>
+#include <linux/acpi.h>
+#include <linux/pm_domain.h>
 
 /**
  * dev_pm_get_subsys_data - Create or refcount power.subsys_data for device.

@@ -82,3 +84,57 @@ int dev_pm_put_subsys_data(struct device *dev)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(dev_pm_put_subsys_data);
+
+/**
+ * dev_pm_domain_attach - Attach a device to its PM domain.
+ * @dev: Device to attach.
+ * @power_on: Used to indicate whether we should power on the device.
+ *
+ * The @dev may only be attached to a single PM domain. By iterating through
+ * the available alternatives we try to find a valid PM domain for the device.
+ *
+ * This function should typically be invoked from subsystem level code during
+ * the probe phase. Especially for those that holds devices which requires
+ * power management through PM domains.
+ *
+ * Callers must ensure proper synchronization of this function with power
+ * management callbacks.
+ *
+ * Returns 0 on successfully attached PM domain or negative error code.
+ */
+int dev_pm_domain_attach(struct device *dev, bool power_on)
+{
+	int ret;
+
+	ret = acpi_dev_pm_attach(dev, power_on);
+	if (!ret || ret == -EPROBE_DEFER)

+		return ret;
+
+	return genpd_dev_pm_attach(dev);

+}
+EXPORT_SYMBOL_GPL(dev_pm_domain_attach);
+
+/**
+ * dev_pm_domain_detach - Detach a device from its PM domain.
+ * @dev: Device to attach.
+ * @power_off: Used to indicate whether we should power off the device.
+ *
+ * The @dev may be attached to a PM domain. By iterating through the available
+ * alternatives we detach it from its PM domain.
+ *
+ * This functions will reverse the actions from dev_pm_domain_attach() and thus
+ * detach the @dev from its PM domain. Typically it should be invoked from
+ * subsystem level code during the remove phase.
+ *
+ * Callers must ensure proper synchronization of this function with power
+ * management callbacks.
+ *
+ * Returns 0 on successfully detached PM domain or negative error code.
+ */
+int dev_pm_domain_detach(struct device *dev, bool power_off)
+{
+	if (acpi_dev_pm_detach(dev, power_off))
+		return genpd_dev_pm_detach(dev);

+	return 0;
+}
+EXPORT_SYMBOL_GPL(dev_pm_domain_detach);

diff --git a/include/linux/pm.h b/include/linux/pm.h
index 72c0fe0..8176b07 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h

@@ -621,6 +621,20 @@ struct dev_pm_domain {
 	struct dev_pm_ops	ops;
 };
 
+#ifdef CONFIG_PM
+extern int dev_pm_domain_attach(struct device *dev, bool power_on);
+extern int dev_pm_domain_detach(struct device *dev, bool power_off);
+#else
+static inline int dev_pm_domain_attach(struct device *dev, bool power_on)
+{
+	return -ENODEV;
+}
+static inline int dev_pm_domain_detach(struct device *dev, bool power_off)
+{
+	return -ENODEV;
+}
+#endif
+
 /*
  * The PM_EVENT_ messages are also used by drivers implementing the legacy
  * suspend framework, based on the ->suspend() and ->resume() callbacks common