platform/chrome: cros_ec_typec: Check for EC device

The Type C ACPI device on older Chromebooks is not generated correctly
(since their EC firmware doesn't support the new commands required). In
such cases, the crafted ACPI device doesn't have an EC parent, and it is
therefore not useful (it shouldn't be generated in the first place since
the EC firmware doesn't support any of the Type C commands).

To handle devices which use these older firmware revisions, check for
the parent EC device handle, and fail the probe if it's not found.

Fixes: fdc6b21 ("platform/chrome: Add Type C connector class driver")
Reported-by: Alyssa Ross <[email protected]>
Reviewed-by: Tzung-Bi Shih <[email protected]>
Signed-off-by: Prashant Malani <[email protected]>
Acked-by: Heikki Krogerus <[email protected]>
Reviewed-by: Alyssa Ross <[email protected]>
Tested-by: Alyssa Ross <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Benson Leung <[email protected]>

drivers/platform/chrome/cros_ec_typec.c

@@ -1076,7 +1076,13 @@ static int cros_typec_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	typec->dev = dev;
+
 	typec->ec = dev_get_drvdata(pdev->dev.parent);
+	if (!typec->ec) {
+		dev_err(dev, "couldn't find parent EC device\n");
+		return -ENODEV;
+	}
+
 	platform_set_drvdata(pdev, typec);
 
 	ret = cros_typec_get_cmd_version(typec);