ACPI: scan: Simplify initialization of power and sleep buttons

It should be perfectly fine to use ACPI if the "fixed" power or sleep
buttons cannot be initialized. Moreover, running acpi_bus_scan()
successfully on ACPI_ROOT_OBJECT generally causes many devices to
be enumerated and probed, possibly including the entire PCI bus, so
unregistering acpi_root if the registration of the "fixed" buttons
fails is rather unhelpful.

For this reason, do not fail acpi_scan_init() when
acpi_bus_scan_fixed() fails and turn the latter into a void function.

While at it, drop the outdated and misleading comment from
acpi_bus_scan_fixed().

Signed-off-by: Rafael J. Wysocki <[e-mail]>
Reviewed-by: Mika Westerberg <[e-mail]>
Reviewed-by: Hans de Goede <[e-mail]>

drivers/acpi/scan.c

···
 }
 EXPORT_SYMBOL_GPL(acpi_bus_register_early_device);
 
-static int acpi_bus_scan_fixed(void)
+static void acpi_bus_scan_fixed(void)
 {
-	int result = 0;
-
-	/*
-	 * Enumerate all fixed-feature devices.
-	 */
 	if (!(acpi_gbl_FADT.flags & ACPI_FADT_POWER_BUTTON)) {
-		struct acpi_device *device = NULL;
+		struct acpi_device *adev = NULL;
 
-		result = acpi_add_single_object(&device, NULL,
-						ACPI_BUS_TYPE_POWER_BUTTON, false);
-		if (result)
-			return result;
-
-		device->flags.match_driver = true;
-		result = device_attach(&device->dev);
-		if (result < 0)
-			return result;
-
-		device_init_wakeup(&device->dev, true);
+		acpi_add_single_object(&adev, NULL, ACPI_BUS_TYPE_POWER_BUTTON,
+				       false);
+		if (adev) {
+			adev->flags.match_driver = true;
+			if (device_attach(&adev->dev) >= 0)
+				device_init_wakeup(&adev->dev, true);
+			else
+				dev_dbg(&adev->dev, "No driver\n");
+		}
 	}
 
 	if (!(acpi_gbl_FADT.flags & ACPI_FADT_SLEEP_BUTTON)) {
-		struct acpi_device *device = NULL;
+		struct acpi_device *adev = NULL;
 
-		result = acpi_add_single_object(&device, NULL,
-						ACPI_BUS_TYPE_SLEEP_BUTTON, false);
-		if (result)
-			return result;
-
-		device->flags.match_driver = true;
-		result = device_attach(&device->dev);
+		acpi_add_single_object(&adev, NULL, ACPI_BUS_TYPE_SLEEP_BUTTON,
+				       false);
+		if (adev) {
+			adev->flags.match_driver = true;
+			if (device_attach(&adev->dev) < 0)
+				dev_dbg(&adev->dev, "No driver\n");
+		}
 	}
-
-	return result < 0 ? result : 0;
 }
 
 static void __init acpi_get_spcr_uart_addr(void)
···
 		goto out;
 
 	/* Fixed feature devices do not exist on HW-reduced platform */
-	if (!acpi_gbl_reduced_hardware) {
-		if (acpi_bus_scan_fixed()) {
-			acpi_detach_data(acpi_root->handle,
-					 acpi_scan_drop_device);
-			acpi_device_del(acpi_root);
-			acpi_bus_put_acpi_device(acpi_root);
-			goto out;
-		}
-	}
+	if (!acpi_gbl_reduced_hardware)
+		acpi_bus_scan_fixed();
 
 	acpi_turn_off_unused_power_resources();