platform/x86: ideapad-laptop: Only toggle ps2 aux port on/off on select models

Recently there have been multiple patches to disable the ideapad-laptop's
touchpad control code, because it is causing issues on various laptops:

Commit d69cd7ee ("platform/x86: ideapad-laptop: Disable touchpad_switch for ELAN0634")
Commit a231224a ("platform/x86: ideapad-laptop: Disable touchpad_switch")

The turning on/off of the ps2 aux port was added specifically for
the IdeaPad Z570, where the EC does toggle the touchpad on/off LED and
toggles the value returned by reading VPCCMD_R_TOUCHPAD, but it does not
actually turn on/off the touchpad.

The ideapad-laptop code really should not be messing with the i8042
controller on all devices just for this special case.

Add a new ctrl_ps2_aux_port flag set based on a DMI based allow-list
for devices which need this workaround, populating it with just
the Ideapad Z570 for now.

This also adds a module parameter so that this behavior can easily
be enabled on other models which may need it.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Tested-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Tested-by: Maxim Mikityanskiy <maxtram95@gmail.com>
Link: https://lore.kernel.org/r/20221117110244.67811-4-hdegoede@redhat.com

drivers/platform/x86/ideapad-laptop.c

@@ -143,6 +143,7 @@ struct ideapad_private {
 		bool hw_rfkill_switch     : 1;
 		bool kbd_bl               : 1;
 		bool touchpad_ctrl_via_ec : 1;
+		bool ctrl_ps2_aux_port    : 1;
 		bool usb_charging         : 1;
 	} features;
 	struct {
@@ -174,6 +175,12 @@ MODULE_PARM_DESC(set_fn_lock_led,
 	"Enable driver based updates of the fn-lock LED on fn-lock changes. "
 	"If you need this please report this to: platform-driver-x86@vger.kernel.org");
 
+static bool ctrl_ps2_aux_port;
+module_param(ctrl_ps2_aux_port, bool, 0444);
+MODULE_PARM_DESC(ctrl_ps2_aux_port,
+	"Enable driver based PS/2 aux port en-/dis-abling on touchpad on/off toggle. "
+	"If you need this please report this to: platform-driver-x86@vger.kernel.org");
+
 /*
  * shared data
  */
@@ -1507,6 +1514,7 @@ static void ideapad_sync_touchpad_state(struct ideapad_private *priv, bool send_
 	 * touchpad off and on. We send KEY_TOUCHPAD_OFF and
 	 * KEY_TOUCHPAD_ON to not to get out of sync with LED
 	 */
+	if (priv->features.ctrl_ps2_aux_port)
 		i8042_command(&param, value ? I8042_CMD_AUX_ENABLE : I8042_CMD_AUX_DISABLE);
 
 	if (send_events) {
@@ -1615,6 +1623,23 @@ static const struct dmi_system_id hw_rfkill_list[] = {
 	{}
 };
 
+/*
+ * On some models the EC toggles the touchpad muted LED on touchpad toggle
+ * hotkey presses, but the EC does not actually disable the touchpad itself.
+ * On these models the driver needs to explicitly enable/disable the i8042
+ * (PS/2) aux port.
+ */
+static const struct dmi_system_id ctrl_ps2_aux_port_list[] = {
+	{
+	/* Lenovo Ideapad Z570 */
+	.matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_VERSION, "Ideapad Z570"),
+		},
+	},
+	{}
+};
+
 static const struct dmi_system_id no_touchpad_switch_list[] = {
 	{
 	.ident = "Lenovo Yoga 3 Pro 1370",
@@ -1642,6 +1667,8 @@ static void ideapad_check_features(struct ideapad_private *priv)
 		set_fn_lock_led || dmi_check_system(set_fn_lock_led_list);
 	priv->features.hw_rfkill_switch =
 		hw_rfkill_switch || dmi_check_system(hw_rfkill_list);
+	priv->features.ctrl_ps2_aux_port =
+		ctrl_ps2_aux_port || dmi_check_system(ctrl_ps2_aux_port_list);
 
 	/* Most ideapads with ELAN0634 touchpad don't use EC touchpad switch */
 	if (acpi_dev_present("ELAN0634", NULL, -1))