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: fdc6b21e ("platform/chrome: Add Type C connector class driver")
Reported-by: NAlyssa Ross <hi@alyssa.is>
Reviewed-by: NTzung-Bi Shih <tzungbi@google.com>
Signed-off-by: NPrashant Malani <pmalani@chromium.org>
Acked-by: NHeikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: NAlyssa Ross <hi@alyssa.is>
Tested-by: NAlyssa Ross <hi@alyssa.is>
Link: https://lore.kernel.org/r/20220126190219.3095419-1-pmalani@chromium.orgSigned-off-by: NBenson Leung <bleung@chromium.org>

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);