ACPI: PM: Unexport acpi_device_get_power()

Using acpi_device_get_power() outside of ACPI device initialization
and ACPI sysfs is problematic due to the way in which power resources
are handled by it, so unexport it and add a paragraph explaining the
pitfalls to its kerneldoc comment.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: NMika Westerberg <mika.westerberg@linux.intel.com>

drivers/acpi/device_pm.c

@@ -53,6 +53,11 @@ const char *acpi_power_state_string(int state)
  * This function does not update the device's power.state field, but it may
  * update its parent's power.state field (when the parent's power state is
  * unknown and the device's power state turns out to be D0).
+ *
+ * Also, it does not update power resource reference counters to ensure that
+ * the power state returned by it will be persistent and it may return a power
+ * state shallower than previously set by acpi_device_set_power() for @device
+ * (if that power state depends on any power resources).
  */
 int acpi_device_get_power(struct acpi_device *device, int *state)
 {
@@ -118,7 +123,6 @@ int acpi_device_get_power(struct acpi_device *device, int *state)
 
 	return 0;
 }
-EXPORT_SYMBOL(acpi_device_get_power);
 
 static int acpi_dev_pm_explicit_set(struct acpi_device *adev, int state)
 {

drivers/acpi/internal.h

@@ -139,8 +139,15 @@ int acpi_power_get_inferred_state(struct acpi_device *device, int *state);
 int acpi_power_on_resources(struct acpi_device *device, int state);
 int acpi_power_transition(struct acpi_device *device, int state);
 
+/* --------------------------------------------------------------------------
+                              Device Power Management
+   -------------------------------------------------------------------------- */
+int acpi_device_get_power(struct acpi_device *device, int *state);
 int acpi_wakeup_device_init(void);
 
+/* --------------------------------------------------------------------------
+                                  Processor
+   -------------------------------------------------------------------------- */
 #ifdef CONFIG_ARCH_MIGHT_HAVE_ACPI_PDC
 void acpi_early_processor_set_pdc(void);
 #else

include/acpi/acpi_bus.h

@@ -506,7 +506,6 @@ int acpi_bus_get_status(struct acpi_device *device);
 
 int acpi_bus_set_power(acpi_handle handle, int state);
 const char *acpi_power_state_string(int state);
-int acpi_device_get_power(struct acpi_device *device, int *state);
 int acpi_device_set_power(struct acpi_device *device, int state);
 int acpi_bus_init_power(struct acpi_device *device);
 int acpi_device_fix_up_power(struct acpi_device *device);