linux-kernel - [PATCH v4 2/3] platform/x86: thinkpad_acpi - Add doubletap

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Message-ID: <20251129002533.9070-3-vishnuocv@gmail.com>
Date: Sat, 29 Nov 2025 09:25:32 +0900
From: Vishnu Sankar <vishnuocv@...il.com>
To: corbet@....net,
	dmitry.torokhov@...il.com,
	hmh@....eng.br,
	derekjohn.clark@...il.com,
	hansg@...nel.org,
	ilpo.jarvinen@...ux.intel.com
Cc: mpearson-lenovo@...ebb.ca,
	linux-doc@...r.kernel.org,
	linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	ibm-acpi-devel@...ts.sourceforge.net,
	platform-driver-x86@...r.kernel.org,
	vsankar@...ovo.com,
	Vishnu Sankar <vishnuocv@...il.com>
Subject: [PATCH v4 2/3] platform/x86: thinkpad_acpi - Add doubletap_filter sysfs interface

Add sysfs interface for controlling TrackPoint doubletap event filtering.
This allows userspace to enable/disable doubletap functionality and
query the current state.

The attribute is available at:
/sys/devices/platform/thinkpad_acpi/doubletap_filter

When set to 1, doubletap events are filtered out (ignored).
When set to 0, doubletap events are processed (default).

This complements the automatic hardware enablement in the trackpoint
driver by providing user control over event processing at the kernel level.

Signed-off-by: Vishnu Sankar <vishnuocv@...il.com>
Suggested-by: Mark Pearson <mpearson-lenovo@...ebb.ca>
---
Changes in v2:
- Updated commit message to clarify dependency on trackpoint driver
- Now handling sysfs read/write of trackpoint driver using file read/write
- Removed sysfs attribute creation of trackpoint double tap here
- Reversed the logic and return false right away
- Dropped unnecessary debug messages
- Using dev_dbg() instead of pr_xxxx()

Changes in v3:
- No changes

Changes in v4:
- Simplified approach: single sysfs attribute for user control
- Clear naming: doubletap_filter instead of doubletap_enabled
- Intuitive behavior: 0=process events, 1=filter events
- No cross-driver dependencies or complex interactions
- Minimal code changes using existing thinkpad_acpi infrastructure
---
---
 drivers/platform/x86/lenovo/thinkpad_acpi.c | 54 +++++++++++++++++++--
 1 file changed, 49 insertions(+), 5 deletions(-)

diff --git a/drivers/platform/x86/lenovo/thinkpad_acpi.c b/drivers/platform/x86/lenovo/thinkpad_acpi.c
index cc19fe520ea9..9b646ecff452 100644
--- a/drivers/platform/x86/lenovo/thinkpad_acpi.c
+++ b/drivers/platform/x86/lenovo/thinkpad_acpi.c
@@ -373,7 +373,7 @@ static struct {
 	u32 hotkey_poll_active:1;
 	u32 has_adaptive_kbd:1;
 	u32 kbd_lang:1;
-	u32 trackpoint_doubletap:1;
+	u32 trackpoint_doubletap_filter:1;
 	struct quirk_entry *quirks;
 } tp_features;
 
@@ -3104,8 +3104,35 @@ static void tpacpi_send_radiosw_update(void)
 	hotkey_radio_sw_notify_change();
 }
 
+static ssize_t doubletap_filter_show(struct device *dev,
+				      struct device_attribute *attr,
+				      char *buf)
+{
+	return sysfs_emit(buf, "%d\n", tp_features.trackpoint_doubletap_filter);
+}
+
+static ssize_t doubletap_filter_store(struct device *dev,
+				       struct device_attribute *attr,
+				       const char *buf, size_t count)
+{
+	bool filter;
+	int err;
+
+	err = kstrtobool(buf, &filter);
+	if (err)
+		return err;
+
+	tp_features.trackpoint_doubletap_filter = filter;
+	return count;
+}
+
+static DEVICE_ATTR_RW(doubletap_filter);
+
 static void hotkey_exit(void)
 {
+	if (tpacpi_pdev)
+		device_remove_file(&tpacpi_pdev->dev, &dev_attr_doubletap_filter);
+
 	mutex_lock(&hotkey_mutex);
 	hotkey_poll_stop_sync();
 	dbg_printk(TPACPI_DBG_EXIT | TPACPI_DBG_HKEY,
@@ -3557,8 +3584,22 @@ static int __init hotkey_init(struct ibm_init_struct *iibm)
 
 	hotkey_poll_setup_safe(true);
 
-	/* Enable doubletap by default */
-	tp_features.trackpoint_doubletap = 1;
+	/*
+	 * Enable kernel-level doubletap event filtering by default.
+	 * This allows doubletap events to reach userspace.
+	 */
+	tp_features.trackpoint_doubletap_filter = 1;
+
+	/* Create doubletap_filter sysfs attribute */
+	if (tpacpi_pdev) {
+		int err = device_create_file(&tpacpi_pdev->dev, &dev_attr_doubletap_filter);
+		if (err) {
+			pr_warn("Unable to create doubletap_filter sysfs attribute\n");
+			/* Continue even if sysfs creation fails */
+		} else {
+			pr_info("ThinkPad ACPI doubletap_filter sysfs attribute created\n");
+		}
+	}
 
 	return 0;
 }
@@ -3863,7 +3904,8 @@ static bool hotkey_notify_8xxx(const u32 hkey, bool *send_acpi_ev)
 {
 	switch (hkey) {
 	case TP_HKEY_EV_TRACK_DOUBLETAP:
-		if (tp_features.trackpoint_doubletap)
+		/* Only send the event if kernel-level filtering allows it */
+		if (tp_features.trackpoint_doubletap_filter)
 			tpacpi_input_send_key(hkey, send_acpi_ev);
 
 		return true;
@@ -11285,7 +11327,9 @@ static bool tpacpi_driver_event(const unsigned int hkey_event)
 		mutex_unlock(&tpacpi_inputdev_send_mutex);
 		return true;
 	case TP_HKEY_EV_DOUBLETAP_TOGGLE:
-		tp_features.trackpoint_doubletap = !tp_features.trackpoint_doubletap;
+		/* Toggle kernel-level doubletap event filtering */
+		tp_features.trackpoint_doubletap_filter =
+			!tp_features.trackpoint_doubletap_filter;
 		return true;
 	case TP_HKEY_EV_PROFILE_TOGGLE:
 	case TP_HKEY_EV_PROFILE_TOGGLE2:
-- 
2.51.0