ACPI: allow a native cpuidle driver to displace ACPI

The ACPI driver would fail probe when it found that
another driver had previously registered with cpuidle.

But this is a natural situation, as a native hardware
cpuidle driver should be able to bind instead of ACPI,
and the ACPI processor driver should be able to handle
yielding control of C-states while still handling
P-states and T-states.

Add a KERN_DEBUG line showing when acpi_idle
does successfully register.
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/processor_driver.c

@@ -616,6 +616,7 @@ static int __cpuinit acpi_processor_add(struct acpi_device *device)
 	acpi_processor_get_limit_info(pr);
 
 
+	if (cpuidle_get_driver() == &acpi_idle_driver)
 		acpi_processor_power_init(pr, device);
 
 	pr->cdev = thermal_cooling_device_register("Processor", device,
@@ -920,9 +921,10 @@ static int __init acpi_processor_init(void)
 	if (!acpi_processor_dir)
 		return -ENOMEM;
 #endif
-	result = cpuidle_register_driver(&acpi_idle_driver);
-	if (result < 0)
-		goto out_proc;
+
+	if (!cpuidle_register_driver(&acpi_idle_driver))
+		printk(KERN_DEBUG "ACPI: %s registered with cpuidle\n",
+			acpi_idle_driver.name);
 
 	result = acpi_bus_register_driver(&acpi_processor_driver);
 	if (result < 0)
@@ -941,7 +943,6 @@ static int __init acpi_processor_init(void)
 out_cpuidle:
 	cpuidle_unregister_driver(&acpi_idle_driver);
 
-out_proc:
 #ifdef CONFIG_ACPI_PROCFS
 	remove_proc_entry(ACPI_PROCESSOR_CLASS, acpi_root_dir);
 #endif