linux-kernel - Wrongly bound Elantech touchpad on Lenovo Yoga Slim 7

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Date:   Fri, 04 Feb 2022 17:57:14 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     linux-input@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Wrongly bound Elantech touchpad on Lenovo Yoga Slim 7

Hi,

we've got a bug report on openSUSE Bugzilla about the broken touchpad
on Lenovo Yoga Slim 7:
  https://bugzilla.opensuse.org/show_bug.cgi?id=1193064

The touchpad is an Elantech one, connected over i2c, and there are two
drivers supporting it.  Unfortunately, the default one the system
binds, elan-i2c input driver, doesn't seem working properly, while
i2c-hid driver works.

I'm not sure what's the best fix for this, but below a quick
workaround using a deny list with DMI matching.
If this is OK, I can resubmit the patch for merging.

Any comments appreciated.


thanks,

Takashi

-- 8< --
From: Takashi Iwai <tiwai@...e.de>
Subject: [PATCH] Input: elan_i2c: Add deny list for Lenovo Yoga Slim 7

The touchpad on Lenovo Yoga Slim 7 doesn't work well with elan-i2c but
rather better with i2c-hid.  Add a deny list for avoiding to bind with
elan-i2c.

BugLink: https://bugzilla.opensuse.org/show_bug.cgi?id=1193064
Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
 drivers/input/mouse/elan_i2c_core.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/input/mouse/elan_i2c_core.c b/drivers/input/mouse/elan_i2c_core.c
index 47af62c12267..fd08481f7aea 100644
--- a/drivers/input/mouse/elan_i2c_core.c
+++ b/drivers/input/mouse/elan_i2c_core.c
@@ -18,6 +18,7 @@
 #include <linux/acpi.h>
 #include <linux/delay.h>
 #include <linux/device.h>
+#include <linux/dmi.h>
 #include <linux/firmware.h>
 #include <linux/i2c.h>
 #include <linux/init.h>
@@ -1222,6 +1223,20 @@ static void elan_disable_regulator(void *_data)
 	regulator_disable(data->vcc);
 }
 
+static const struct dmi_system_id elan_i2c_denylist[] __initconst = {
+#if IS_ENABLED(CONFIG_I2C_HID_ACPI)
+	{
+		/* Lenovo Yoga Slim 7 is better supported by i2c-hid */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "82A3"),
+			DMI_MATCH(DMI_PRODUCT_VERSION, "Yoga Slim 7 14ITL05"),
+		},
+	},
+#endif
+	{ }
+};
+
 static int elan_probe(struct i2c_client *client,
 		      const struct i2c_device_id *dev_id)
 {
@@ -1233,6 +1248,10 @@ static int elan_probe(struct i2c_client *client,
 
 	if (IS_ENABLED(CONFIG_MOUSE_ELAN_I2C_I2C) &&
 	    i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
+		if (dmi_check_system(elan_i2c_denylist)) {
+			dev_info(dev, "Hits deny list, skipping\n");
+			return -ENODEV;
+		}
 		transport_ops = &elan_i2c_ops;
 	} else if (IS_ENABLED(CONFIG_MOUSE_ELAN_I2C_SMBUS) &&
 		   i2c_check_functionality(client->adapter,
-- 
2.31.1