From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
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: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
On top of the linux-next branch in the linux-pm.git tree.
---
drivers/acpi/device_pm.c | 6 +++++-
drivers/acpi/internal.h | 7 +++++++
include/acpi/acpi_bus.h | 1 -
3 files changed, 12 insertions(+), 2 deletions(-)
Index: linux-pm/drivers/acpi/device_pm.c
===================================================================
--- linux-pm.orig/drivers/acpi/device_pm.c
+++ linux-pm/drivers/acpi/device_pm.c
@@ -66,6 +66,11 @@ static int acpi_dev_pm_explicit_get(stru
* 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)
{
@@ -130,7 +135,6 @@ int acpi_device_get_power(struct acpi_de
return 0;
}
-EXPORT_SYMBOL(acpi_device_get_power);
static int acpi_dev_pm_explicit_set(struct acpi_device *adev, int state)
{
Index: linux-pm/include/acpi/acpi_bus.h
===================================================================
--- linux-pm.orig/include/acpi/acpi_bus.h
+++ linux-pm/include/acpi/acpi_bus.h
@@ -506,7 +506,6 @@ int acpi_bus_get_status(struct acpi_devi
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);
Index: linux-pm/drivers/acpi/internal.h
===================================================================
--- linux-pm.orig/drivers/acpi/internal.h
+++ linux-pm/drivers/acpi/internal.h
@@ -139,8 +139,15 @@ int acpi_power_get_inferred_state(struct
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
