[PATCH v1 1/2] hpet: Check ACPI_COMPANION() against NULL at probe time

["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
hpet driver.

Fixes: 71f0a267346b ("hpet: Convert ACPI driver to a platform one")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/char/hpet.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/char/hpet.c
+++ b/drivers/char/hpet.c
@@ -976,10 +976,14 @@ static acpi_status hpet_resources(struct
 
 static int hpet_acpi_probe(struct platform_device *pdev)
 {
-	struct acpi_device *device = ACPI_COMPANION(&pdev->dev);
+	struct acpi_device *device;
 	acpi_status result;
 	struct hpet_data data;
 
+	device = ACPI_COMPANION(&pdev->dev);
+	if (!device)
+		return -ENODEV;
+
 	memset(&data, 0, sizeof(data));
 
 	result =