Input: cros_ec_keyb - Defer probe until parent EC device is registered

The `cros_ec_keyb` driver can be probed before the cros_ec_device has
completed the registration.  This creates a race condition where
`cros_ec_keyb` might access uninitialized data.

Fix this by calling `cros_ec_device_registered()` to check the parent's
status.  If the device is not yet ready, return -EPROBE_DEFER to ensure
the probe is retried later.

Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Link: https://lore.kernel.org/r/20250828083601.856083-6-tzungbi@kernel.org
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>

Author: Tzung-Bi Shih

drivers/input/keyboard/cros_ec_keyb.c

@@ -705,6 +705,12 @@ static int cros_ec_keyb_probe(struct platform_device *pdev)
 	ec = dev_get_drvdata(pdev->dev.parent);
 	if (!ec)
 		return -EPROBE_DEFER;
+	/*
+	 * Even if the cros_ec_device pointer is available, still need to check
+	 * if the device is fully registered before using it.
+	 */
+	if (!cros_ec_device_registered(ec))
+		return -EPROBE_DEFER;
 
 	ckdev = devm_kzalloc(dev, sizeof(*ckdev), GFP_KERNEL);
 	if (!ckdev)