[PATCH v1] ACPI: PAD: xen: Check ACPI_COMPANION() against NULL

["Rafael J. Wysocki" <rafael@kernel.org>]

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

Every platform driver can be forced to match a device that doesn't match
its list of device IDs because of device_match_driver_override(), so
platform drivers that rely on the existence of a device's ACPI companion
object need to verify its presence.

Accordingly, add a requisite ACPI_COMPANION() check against NULL to the
Xen variant of the ACPI processor aggregator device (PAD) driver.

Fixes: 112b2f978afe ("ACPI: PAD: xen: Convert to a platform driver")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/xen/xen-acpi-pad.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/xen/xen-acpi-pad.c
+++ b/drivers/xen/xen-acpi-pad.c
@@ -110,9 +110,13 @@ static void acpi_pad_notify(acpi_handle
 
 static int acpi_pad_probe(struct platform_device *pdev)
 {
-	struct acpi_device *device = ACPI_COMPANION(&pdev->dev);
+	struct acpi_device *device;
 	acpi_status status;
 
+	device = ACPI_COMPANION(&pdev->dev);
+	if (!device)
+		return -ENODEV;
+
 	strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
 	strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);