ACPI / PM: Introduce __acpi_bus_get_power()

It sometimes is necessary to get the power state of an ACPI device
without updating its device->power.state field, for example to
avoid inconsistencies between device->power.state and the reference
counters of the device's power resources.  For this purpose introduce
__acpi_bus_get_power() that will return the given device's power
state via a pointer (instead of modifying device->power.state)
and make acpi_bus_get_power() use it.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 29 insertions, 19 deletions

diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index a9fe8e6bc40e..9657abc4a7fb 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -196,34 +196,24 @@ EXPORT_SYMBOL(acpi_bus_get_private_data);
                                  Power Management
    -------------------------------------------------------------------------- */
 
-int acpi_bus_get_power(acpi_handle handle, int *state)
+static int __acpi_bus_get_power(struct acpi_device *device, int *state)
 {
         int result = 0;
         acpi_status status = 0;
-        struct acpi_device *device = NULL;
         unsigned long long psc = 0;
 
-
-        result = acpi_bus_get_device(handle, &device);
-        if (result)
-                return result;
+        if (!device || !state)
+                return -EINVAL;
 
         *state = ACPI_STATE_UNKNOWN;
 
-        if (!device->flags.power_manageable) {
-                /* TBD: Non-recursive algorithm for walking up hierarchy */
-                if (device->parent)
-                        *state = device->parent->power.state;
-                else
-                        *state = ACPI_STATE_D0;
-        } else {
+        if (device->flags.power_manageable) {
                 /*
                  * Get the device's power state either directly (via _PSC) or
                  * indirectly (via power resources).
                  */
                 if (device->power.flags.power_resources) {
-                        result = acpi_power_get_inferred_state(device,
-                                                        &device->power.state);
+                        result = acpi_power_get_inferred_state(device, state);
                         if (result)
                                 return result;
                 } else if (device->power.flags.explicit_get) {
@@ -231,20 +221,40 @@ int acpi_bus_get_power(acpi_handle handle, int *state)
                                                        NULL, &psc);
                         if (ACPI_FAILURE(status))
                                 return -ENODEV;
-                        device->power.state = (int)psc;
+                        *state = (int)psc;
                 }
-
-                *state = device->power.state;
+        } else {
+                /* TBD: Non-recursive algorithm for walking up hierarchy. */
+                *state = device->parent ?
+                        device->parent->power.state : ACPI_STATE_D0;
         }
 
         ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Device [%s] power state is D%d\n",
-                          device->pnp.bus_id, device->power.state));
+                          device->pnp.bus_id, *state));
 
         return 0;
 }
 
+
+int acpi_bus_get_power(acpi_handle handle, int *state)
+{
+        struct acpi_device *device;
+        int result;
+
+        result = acpi_bus_get_device(handle, &device);
+        if (result)
+                return result;
+
+        result = __acpi_bus_get_power(device, state);
+        if (result)
+                return result;
+
+        device->power.state = *state;
+        return 0;
+}
 EXPORT_SYMBOL(acpi_bus_get_power);
 
+
 int acpi_bus_set_power(acpi_handle handle, int state)
 {
         int result = 0;