[PATCH v6 1/2] platform/x86/lenovo: lenovo-ymc: Suppress probe on Yoga Book 9 14IAH10

[Dave Carey <carvsdriver@gmail.com>]

The Yoga Book 9 14IAH10 (DMI product name "83KJ") has a dedicated
yb9-kbdock WMI driver that registers an input device reporting
SW_TABLET_MODE to track the detachable Bluetooth keyboard.

lenovo-ymc also loads on this machine and creates an input node with the
SW_TABLET_MODE capability bit set.  For input switches, the presence of
the capability bit has semantic meaning: userspace (e.g. GNOME) reads
the switch state at startup from every node advertising the capability
and does not expect more than one such node.

Add a DMI match for the Yoga Book 9 14IAH10 to probe() so that
lenovo-ymc returns -ENODEV on this hardware, leaving yb9-kbdock as the
sole SW_TABLET_MODE source.  The ymc_ec_trigger EC write, the only
other action taken in response to a YMC event, is guarded by a separate
DMI table that excludes this machine; no other functionality is affected.

Signed-off-by: Dave Carey <carvsdriver@gmail.com>
---
 drivers/platform/x86/lenovo/ymc.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/platform/x86/lenovo/ymc.c b/drivers/platform/x86/lenovo/ymc.c
--- a/drivers/platform/x86/lenovo/ymc.c
+++ b/drivers/platform/x86/lenovo/ymc.c
@@ -23,7 +23,23 @@ module_param(force, bool, 0444);
 static bool force;
 module_param(force, bool, 0444);
 MODULE_PARM_DESC(force, "Force loading on boards without a convertible DMI chassis-type");

+static const struct dmi_system_id lenovo_ymc_nosupport_dmi_table[] = {
+	{
+		/*
+		 * Yoga Book 9 14IAH10: SW_TABLET_MODE is reported by the
+		 * yb9-kbdock driver.  Suppress lenovo-ymc on this machine to
+		 * avoid userspace seeing two input nodes that both advertise
+		 * the SW_TABLET_MODE capability.
+		 */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "83KJ"),
+		},
+	},
+	{ }
+};
+
 static const struct dmi_system_id allowed_chasis_types_dmi_table[] = {
 	{
 		.matches = {
@@ -100,7 +116,10 @@ static int lenovo_ymc_probe(struct wmi_device *wdev, const void *ctx)
 	struct lenovo_ymc_private *priv;
 	struct input_dev *input_dev;
 	int err;

+	if (dmi_check_system(lenovo_ymc_nosupport_dmi_table))
+		return -ENODEV;
+
 	if (!dmi_check_system(allowed_chasis_types_dmi_table)) {
 		if (force)
 			dev_info(&wdev->dev, "Force loading Lenovo YMC support\n");
--
2.54.0