platform/x86: ideapad-laptop: Disable touchpad_switch for ELAN0634

Newer ideapads (e.g.: Yoga 14s, 720S 14) come with ELAN0634 touchpad do not
use EC to switch touchpad.

Reading VPCCMD_R_TOUCHPAD will return zero thus touchpad may be blocked
unexpectedly.
Writing VPCCMD_W_TOUCHPAD may cause a spurious key press.

Add has_touchpad_switch to workaround these machines.
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: stable@vger.kernel.org # 5.4+
--
v2: Specify touchpad to ELAN0634
v3: Stupid missing ! in v2
v4: Correct acpi_dev_present usage (Hans)
Link: https://lore.kernel.org/r/20210107144438.12605-1-jiaxun.yang@flygoat.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/ideapad-laptop.c

@@ -92,6 +92,7 @@ struct ideapad_private {
 	struct dentry *debug;
 	unsigned long cfg;
 	bool has_hw_rfkill_switch;
+	bool has_touchpad_switch;
 	const char *fnesc_guid;
 };
 
@@ -535,7 +536,9 @@ static umode_t ideapad_is_visible(struct kobject *kobj,
 	} else if (attr == &dev_attr_fn_lock.attr) {
 		supported = acpi_has_method(priv->adev->handle, "HALS") &&
 			acpi_has_method(priv->adev->handle, "SALS");
-	} else
+	} else if (attr == &dev_attr_touchpad.attr)
+		supported = priv->has_touchpad_switch;
+	else
 		supported = true;
 
 	return supported ? attr->mode : 0;
@@ -867,6 +870,9 @@ static void ideapad_sync_touchpad_state(struct ideapad_private *priv)
 {
 	unsigned long value;
 
+	if (!priv->has_touchpad_switch)
+		return;
+
 	/* Without reading from EC touchpad LED doesn't switch state */
 	if (!read_ec_data(priv->adev->handle, VPCCMD_R_TOUCHPAD, &value)) {
 		/* Some IdeaPads don't really turn off touchpad - they only
@@ -989,6 +995,9 @@ static int ideapad_acpi_add(struct platform_device *pdev)
 	priv->platform_device = pdev;
 	priv->has_hw_rfkill_switch = dmi_check_system(hw_rfkill_list);
 
+	/* Most ideapads with ELAN0634 touchpad don't use EC touchpad switch */
+	priv->has_touchpad_switch = !acpi_dev_present("ELAN0634", NULL, -1);
+
 	ret = ideapad_sysfs_init(priv);
 	if (ret)
 		return ret;
@@ -1006,6 +1015,10 @@ static int ideapad_acpi_add(struct platform_device *pdev)
 	if (!priv->has_hw_rfkill_switch)
 		write_ec_cmd(priv->adev->handle, VPCCMD_W_RF, 1);
 
+	/* The same for Touchpad */
+	if (!priv->has_touchpad_switch)
+		write_ec_cmd(priv->adev->handle, VPCCMD_W_TOUCHPAD, 1);
+
 	for (i = 0; i < IDEAPAD_RFKILL_DEV_NUM; i++)
 		if (test_bit(ideapad_rfk_data[i].cfgbit, &priv->cfg))
 			ideapad_register_rfkill(priv, i);