[PATCH v7 2/3] platform/x86: thinkpad_acpi: Add sysfs control for TrackPoint double-tap

[Vishnu Sankar <vishnuocv@gmail.com>]

Add a sysfs attribute to enable or disable TrackPoint double-tap hotkey
events at the kernel level.

The TrackPoint firmware enables double-tap support automatically. This
interface allows userspace to control whether double-tap events are
forwarded to userspace.

The attribute is available at:

  /sys/devices/platform/thinkpad_acpi/doubletap_enable

  0 - Disable double-tap hotkey events
  1 - Enable double-tap hotkey events (default)

Filtering is implemented by suppressing ACPI hotkey delivery without
injecting synthetic input events.

Signed-off-by: Vishnu Sankar <vishnuocv@gmail.com>
Suggested-by: Mark Pearson <mpearson-lenovo@squebb.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

Changes in v5:
- Rename doubletap_filter to doubletap_enable to match actual behavior
- Fix inverted logic so events are emitted only when doubletap is enabled
- Register sysfs attribute via hotkey_attributes[] (no device_create_file)
---
---
 drivers/platform/x86/lenovo/thinkpad_acpi.c | 42 +++++++++++++++++----
 1 file changed, 35 insertions(+), 7 deletions(-)

diff --git a/drivers/platform/x86/lenovo/thinkpad_acpi.c b/drivers/platform/x86/lenovo/thinkpad_acpi.c
index cc19fe520ea9..ca01323c990a 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_enable:1;
 	struct quirk_entry *quirks;
 } tp_features;
 
@@ -3018,6 +3018,31 @@ static const struct attribute_group adaptive_kbd_attr_group = {
 	.attrs = adaptive_kbd_attributes,
 };
 
+/* sysfs doubletap enable --------------------------------------------- */
+static ssize_t doubletap_enable_show(struct device *dev,
+				     struct device_attribute *attr,
+				     char *buf)
+{
+	return sysfs_emit(buf, "%d\n", tp_features.trackpoint_doubletap_enable);
+}
+
+static ssize_t doubletap_enable_store(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf, size_t count)
+{
+	bool enable;
+	int err;
+
+	err = kstrtobool(buf, &enable);
+	if (err)
+		return err;
+
+	tp_features.trackpoint_doubletap_enable = enable;
+	return count;
+}
+
+static DEVICE_ATTR_RW(doubletap_enable);
+
 /* --------------------------------------------------------------------- */
 
 static struct attribute *hotkey_attributes[] = {
@@ -3032,6 +3057,7 @@ static struct attribute *hotkey_attributes[] = {
 	&dev_attr_hotkey_recommended_mask.attr,
 	&dev_attr_hotkey_tablet_mode.attr,
 	&dev_attr_hotkey_radio_sw.attr,
+	&dev_attr_doubletap_enable.attr,
 #ifdef CONFIG_THINKPAD_ACPI_HOTKEY_POLL
 	&dev_attr_hotkey_source_mask.attr,
 	&dev_attr_hotkey_poll_freq.attr,
@@ -3557,8 +3583,8 @@ 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 TrackPoint doubletap event reporting by default. */
+	tp_features.trackpoint_doubletap_enable = 1;
 
 	return 0;
 }
@@ -3863,9 +3889,9 @@ 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)
-			tpacpi_input_send_key(hkey, send_acpi_ev);
-
+		/* Only send event if doubletap is enabled */
+		if (!tp_features.trackpoint_doubletap_enable)
+			*send_acpi_ev = false;
 		return true;
 	default:
 		return false;
@@ -11285,7 +11311,9 @@ 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_enable =
+			!tp_features.trackpoint_doubletap_enable;
 		return true;
 	case TP_HKEY_EV_PROFILE_TOGGLE:
 	case TP_HKEY_EV_PROFILE_TOGGLE2:
-- 
2.51.0