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From:   Prashant Malani <pmalani@chromium.org>
To:     linux-kernel@vger.kernel.org
Cc:     Prashant Malani <pmalani@chromium.org>, Alyssa Ross <hi@alyssa.is>,
        Tzung-Bi Shih <tzungbi@google.com>,
        Benson Leung <bleung@chromium.org>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        Guenter Roeck <groeck@chromium.org>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>
Subject: [PATCH v2] platform/chrome: cros_ec_typec: Check for EC device
Date:   Wed, 26 Jan 2022 19:02:20 +0000
Message-Id: <20220126190219.3095419-1-pmalani@chromium.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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: fdc6b21e2444 ("platform/chrome: Add Type C connector class driver")
Reported-by: Alyssa Ross <hi@alyssa.is>
Reviewed-by: Tzung-Bi Shih <tzungbi@google.com>
Signed-off-by: Prashant Malani <pmalani@chromium.org>
---
Hi Alyssa, could you kindly test this with your existing setup? Thanks!

Changes in v2:
- Added newlines as suggested by reviewers.
- Added Reviewed-by tag from Tzung-Bi.

 drivers/platform/chrome/cros_ec_typec.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
index 5de0bfb0bc4d..952c1756f59e 100644
--- a/drivers/platform/chrome/cros_ec_typec.c
+++ b/drivers/platform/chrome/cros_ec_typec.c
@@ -1075,7 +1075,13 @@ 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);
-- 
2.35.0.rc0.227.g00780c9af4-goog