Re: [PATCH v3] platform/x86: ideapad-laptop: do not poke keyboard controller

["Alice Mikityanska" <alice.kernel@fastmail.im>]

On Thu, Oct 22, 2026, at 07:50, Dmitry Torokhov wrote:
> On Ideapad Z570 the driver tries to disable and re-enable data coming
> from the touchpad by poking directly into 8042 keyboard controller.
> This may coincide with the controller resuming and leads to spews in
> dmesg and potentially other instabilities.
>
> Instead of using i8042_command() to control the touchpad state create
> an input handler that serves as a filter and drop events coming from
> the touchpad when it is supposed to be off.
>
> Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> ---
>
> v3:
> - add missing header includes (compiler.h, container_of.h, errno.h,
>   mod_devicetable.h, slab.h, spinlock.h)
> - drop stray blank line in ideapad_tpswitch_filter()
> - collect Reviewed-by from Mark Pearson
>
> v2:
> - fix inverted condition in ideapad_tpswitch_filter()
> - mark the handler as passive_observer so that touchpad is not activated
>   until there are real users
> - use READ_ONCE()/WRITE_ONCE() to access shared state flag
> - drop stray semicolon in to_tpswitch_handle()
> - update comments
>
>  drivers/platform/x86/lenovo/ideapad-laptop.c | 189 ++++++++++++++++++-
>  1 file changed, 180 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/platform/x86/lenovo/ideapad-laptop.c 
> b/drivers/platform/x86/lenovo/ideapad-laptop.c
> index 8213524504ee..be890e82b9ef 100644
> --- a/drivers/platform/x86/lenovo/ideapad-laptop.c
> +++ b/drivers/platform/x86/lenovo/ideapad-laptop.c
> @@ -14,23 +14,28 @@
>  #include <linux/bitops.h>
>  #include <linux/bug.h>
>  #include <linux/cleanup.h>
> +#include <linux/compiler.h>
> +#include <linux/container_of.h>
>  #include <linux/debugfs.h>
>  #include <linux/delay.h>
>  #include <linux/device.h>
>  #include <linux/dmi.h>
> -#include <linux/i8042.h>
> +#include <linux/errno.h>
>  #include <linux/init.h>
>  #include <linux/input.h>
>  #include <linux/input/sparse-keymap.h>
>  #include <linux/jiffies.h>
>  #include <linux/kernel.h>
>  #include <linux/leds.h>
> +#include <linux/mod_devicetable.h>
>  #include <linux/module.h>
>  #include <linux/platform_device.h>
>  #include <linux/platform_profile.h>
>  #include <linux/power_supply.h>
>  #include <linux/rfkill.h>
>  #include <linux/seq_file.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
>  #include <linux/string_choices.h>
>  #include <linux/sysfs.h>
>  #include <linux/types.h>
> @@ -210,6 +215,13 @@ struct ideapad_private {
>  		struct led_classdev led;
>  		unsigned int last_brightness;
>  	} fn_lock;
> +	struct {
> +		bool initialized;
> +		bool active; /* true means touchpad is enabled */
> +		struct input_handler handler;
> +		struct input_dev *tp_dev;
> +		spinlock_t lock;
> +	} tp_switch;
>  };
> 
>  static bool no_bt_rfkill;
> @@ -234,7 +246,7 @@ MODULE_PARM_DESC(set_fn_lock_led,
>  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");
> +		 "Enable driver based suppression of touchpad events on touchpad 
> on/off toggle. If you need this please report this to: 
> platform-driver-x86@vger.kernel.org");
> 
>  static bool touchpad_ctrl_via_ec;
>  module_param(touchpad_ctrl_via_ec, bool, 0444);
> @@ -1462,6 +1474,159 @@ static void 
> ideapad_check_special_buttons(struct ideapad_private *priv)
>  	}
>  }
> 
> +struct ideapad_tpswitch_handle {
> +	struct input_handle handle;
> +	struct ideapad_private *priv;
> +};
> +
> +#define to_tpswitch_handle(h) \
> +	container_of(h, struct ideapad_tpswitch_handle, handle)
> +
> +static int ideapad_tpswitch_connect(struct input_handler *handler,
> +				    struct input_dev *dev,
> +				    const struct input_device_id *id)
> +{
> +	struct ideapad_private *priv =
> +		container_of(handler, struct ideapad_private, tp_switch.handler);
> +	struct ideapad_tpswitch_handle *h;
> +	int error;
> +
> +	h = kzalloc_obj(*h);
> +	if (!h)
> +		return -ENOMEM;
> +
> +	h->priv = priv;
> +	h->handle.dev = dev;
> +	h->handle.handler = handler;
> +	h->handle.name = "ideapad-tpswitch";
> +
> +	error = input_register_handle(&h->handle);
> +	if (error)
> +		goto err_free_handle;
> +
> +	/*
> +	 * We need to open the input handle so the input core invokes our
> +	 * filter, but since we mark our handler as passive observer, this
> +	 * will not cause the underlying touchpad hardware to be started
> +	 * if there are no other users.
> +	 */
> +	error = input_open_device(&h->handle);
> +	if (error)
> +		goto err_unregister_handle;
> +
> +	scoped_guard(spinlock_irq, &priv->tp_switch.lock)
> +		priv->tp_switch.tp_dev = dev;
> +
> +	return 0;
> +
> +err_unregister_handle:
> +	input_unregister_handle(&h->handle);
> +err_free_handle:
> +	kfree(h);
> +	return error;
> +}
> +
> +static void ideapad_tpswitch_disconnect(struct input_handle *handle)
> +{
> +	struct ideapad_tpswitch_handle *h = to_tpswitch_handle(handle);
> +	struct ideapad_private *priv = h->priv;
> +
> +	scoped_guard(spinlock_irq, &priv->tp_switch.lock)
> +		priv->tp_switch.tp_dev = NULL;
> +
> +	input_close_device(handle);
> +	input_unregister_handle(handle);
> +	kfree(h);
> +}
> +
> +static bool ideapad_tpswitch_filter(struct input_handle *handle,
> +				    unsigned int type, unsigned int code,
> +				    int value)
> +{
> +	struct ideapad_tpswitch_handle *h = to_tpswitch_handle(handle);
> +	struct ideapad_private *priv = h->priv;
> +
> +	if (READ_ONCE(priv->tp_switch.active))
> +		return false;
> +
> +	/* Allow passing button release events, drop everything else */
> +	return !(type == EV_KEY && value == 0) &&
> +	       !(type == EV_SYN && code == SYN_REPORT);
> +}
> +
> +static const struct input_device_id ideapad_tpswitch_ids[] = {
> +	{
> +		.flags = INPUT_DEVICE_ID_MATCH_EVBIT |
> +				INPUT_DEVICE_ID_MATCH_KEYBIT |
> +				INPUT_DEVICE_ID_MATCH_ABSBIT,
> +		.bustype = BUS_I8042,
> +		.vendor = 0x0002,
> +		.evbit = { BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS) },
> +		.keybit = { [BIT_WORD(BTN_TOOL_FINGER)] =
> +				BIT_MASK(BTN_TOOL_FINGER) },
> +		.absbit = { BIT_MASK(ABS_X) | BIT_MASK(ABS_Y) |
> +				BIT_MASK(ABS_PRESSURE) |
> +				BIT_MASK(ABS_TOOL_WIDTH) },
> +	},
> +	{ }
> +};
> +
> +static int ideapad_tpswitch_init(struct ideapad_private *priv)
> +{
> +	int error;
> +
> +	if (!priv->features.ctrl_ps2_aux_port)
> +		return 0;
> +
> +	spin_lock_init(&priv->tp_switch.lock);
> +
> +	priv->tp_switch.handler.name = "ideapad-tpswitch";
> +	priv->tp_switch.handler.id_table = ideapad_tpswitch_ids;
> +	priv->tp_switch.handler.filter = ideapad_tpswitch_filter;
> +	priv->tp_switch.handler.connect = ideapad_tpswitch_connect;
> +	priv->tp_switch.handler.disconnect = ideapad_tpswitch_disconnect;
> +	priv->tp_switch.handler.passive_observer = true;
> +
> +	error = input_register_handler(&priv->tp_switch.handler);
> +	if (error) {
> +		dev_err(&priv->platform_device->dev,
> +			"failed to register touchpad switch handler: %d",
> +			error);
> +		return error;
> +	}
> +
> +	priv->tp_switch.initialized = true;
> +	return 0;
> +}
> +
> +static void ideapad_tpswitch_exit(struct ideapad_private *priv)
> +{
> +	if (priv->tp_switch.initialized) {
> +		input_unregister_handler(&priv->tp_switch.handler);
> +		priv->tp_switch.initialized = false;
> +	}
> +}
> +
> +static void ideapad_tpswitch_toggle(struct ideapad_private *priv, bool 
> on)
> +{
> +	guard(spinlock_irq)(&priv->tp_switch.lock);
> +
> +	WRITE_ONCE(priv->tp_switch.active, on);
> +	if (!on) {
> +		struct input_dev *tp_dev = priv->tp_switch.tp_dev;
> +		if (tp_dev) {
> +			input_report_key(tp_dev, BTN_TOUCH, 0);
> +			input_report_key(tp_dev, BTN_TOOL_FINGER, 0);
> +			input_report_key(tp_dev, BTN_TOOL_DOUBLETAP, 0);
> +			input_report_key(tp_dev, BTN_TOOL_TRIPLETAP, 0);
> +			input_report_key(tp_dev, BTN_LEFT, 0);
> +			input_report_key(tp_dev, BTN_RIGHT, 0);
> +			input_report_key(tp_dev, BTN_MIDDLE, 0);

Hello!

Tested-by: Alice Mikityanska <alice.kernel@fastmail.im>

Seems to work well, without any "lost synchronization" messages in
dmesg. There is a new effect, caused by the above lines: if the finger
stays on the surface the entire time, and the user disables and enables
the touchpad, the pointer won't move until the user lifts the finger and
puts it back. Although it's unlikely to break anyone's workflow, I need
to double-check that the evdev doesn't emit some invalid sequence of
events, e.g., touch 0 followed by some movements, or touch 0 followed by
another touch 0.

> +			input_sync(tp_dev);
> +		}
> +	}
> +}
> +
>  /*
>   * backlight
>   */
> @@ -1799,7 +1964,6 @@ static void ideapad_fn_lock_led_exit(struct 
> ideapad_private *priv)
>  static void ideapad_sync_touchpad_state(struct ideapad_private *priv, 
> bool send_events)
>  {
>  	unsigned long value;
> -	unsigned char param;
>  	int ret;
> 
>  	/* Without reading from EC touchpad LED doesn't switch state */
> @@ -1810,12 +1974,11 @@ static void ideapad_sync_touchpad_state(struct 
> ideapad_private *priv, bool send_
> 
>  	/*
>  	 * Some IdeaPads don't really turn off touchpad - they only
> -	 * switch the LED state. We (de)activate KBC AUX port to turn
> -	 * touchpad off and on. We send KEY_TOUCHPAD_OFF and
> -	 * KEY_TOUCHPAD_ON to not to get out of sync with LED
> +	 * switch the LED state. On such devices we use an input filter to
> +	 * suppress events from the touchpad.
>  	 */
>  	if (priv->features.ctrl_ps2_aux_port)
> -		i8042_command(&param, value ? I8042_CMD_AUX_ENABLE : I8042_CMD_AUX_DISABLE);
> +		ideapad_tpswitch_toggle(priv, value);
> 
>  	/*
>  	 * On older models the EC controls the touchpad and toggles it on/off
> @@ -2018,8 +2181,8 @@ 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.
> + * On these models the driver needs to explicitly suppress data coming from
> + * the touchpad.
>   */
>  static const struct dmi_system_id ctrl_ps2_aux_port_list[] = {
>  	{
> @@ -2402,6 +2565,10 @@ static int ideapad_acpi_add(struct platform_device *pdev)
>  	if (err)
>  		goto input_failed;
> 
> +	err = ideapad_tpswitch_init(priv);
> +	if (err)
> +		goto tpswitch_failed;
> +
>  	err = ideapad_kbd_bl_init(priv);
>  	if (err) {
>  		if (err != -ENODEV)
> @@ -2478,6 +2645,9 @@ static int ideapad_acpi_add(struct platform_device *pdev)
> 
>  	ideapad_fn_lock_led_exit(priv);
>  	ideapad_kbd_bl_exit(priv);
> +	ideapad_tpswitch_exit(priv);
> +
> +tpswitch_failed:
>  	ideapad_input_exit(priv);
> 
>  input_failed:
> @@ -2507,6 +2677,7 @@ static void ideapad_acpi_remove(struct 
> platform_device *pdev)
> 
>  	ideapad_fn_lock_led_exit(priv);
>  	ideapad_kbd_bl_exit(priv);
> +	ideapad_tpswitch_exit(priv);
>  	ideapad_input_exit(priv);
>  	ideapad_debugfs_exit(priv);
>  }
>
> -- 
> Dmitry