[PATCH v3 1/3] input: mouse: trackpoint: Add doubletap enable/disable support

[PATCH v3 1/3] input: mouse: trackpoint: Add doubletap enable/disable support

[Vishnu Sankar]

Add support for enabling and disabling doubletap on TrackPoint devices
that support this functionality. The feature is detected using firmware
ID and exposed via sysfs as `doubletap_enabled`.

The feature is only available on newer ThinkPads (2023 and later).The driver
exposes this capability via a new sysfs attribute:
"/sys/bus/serio/devices/seriox/doubletap_enabled".

The attribute is only created if the device is detected to be capable of
doubletap via firmware and variant ID checks. This functionality will be
used by platform drivers such as thinkpad_acpi to expose and control doubletap
via user interfaces.

Signed-off-by: Vishnu Sankar <vishnuocv@gmail.com>
Suggested-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Suggested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
Changes in v2:
- Improve commit messages
- Sysfs attributes moved to trackpoint.c
- Removed unnecessary comments
- Removed unnecessary debug messages
- Using strstarts() instead of strcmp()
- is_trackpoint_dt_capable() modified
- Removed _BIT suffix and used BIT() define.
- Reverse the trackpoint_doubletap_status() logic to return error first.
- Removed export functions as a result of the design change
- Changed trackpoint_dev->psmouse to parent_psmouse
- The path of trackpoint.h is not changed.
Changes in v3:
- No changes.
---
 drivers/input/mouse/trackpoint.c | 149 +++++++++++++++++++++++++++++++
 drivers/input/mouse/trackpoint.h |  15 ++++
 2 files changed, 164 insertions(+)

diff --git a/drivers/input/mouse/trackpoint.c b/drivers/input/mouse/trackpoint.c
index 5f6643b69a2c..c6f17b0dec3a 100644
--- a/drivers/input/mouse/trackpoint.c
+++ b/drivers/input/mouse/trackpoint.c
@@ -16,6 +16,8 @@
 #include "psmouse.h"
 #include "trackpoint.h"
 
+static struct trackpoint_data *trackpoint_dev;
+
 static const char * const trackpoint_variants[] = {
 	[TP_VARIANT_IBM]		= "IBM",
 	[TP_VARIANT_ALPS]		= "ALPS",
@@ -63,6 +65,21 @@ static int trackpoint_write(struct ps2dev *ps2dev, u8 loc, u8 val)
 	return ps2_command(ps2dev, param, MAKE_PS2_CMD(3, 0, TP_COMMAND));
 }
 
+/* Read function for TrackPoint extended registers */
+static int trackpoint_extended_read(struct ps2dev *ps2dev, u8 loc, u8 *val)
+{
+	u8 ext_param[2] = {TP_READ_MEM, loc};
+	int error;
+
+	error = ps2_command(ps2dev,
+			    ext_param, MAKE_PS2_CMD(2, 1, TP_COMMAND));
+
+	if (!error)
+		*val = ext_param[0];
+
+	return error;
+}
+
 static int trackpoint_toggle_bit(struct ps2dev *ps2dev, u8 loc, u8 mask)
 {
 	u8 param[3] = { TP_TOGGLE, loc, mask };
@@ -393,6 +410,131 @@ static int trackpoint_reconnect(struct psmouse *psmouse)
 	return 0;
 }
 
+/* List of known incapable device PNP IDs */
+static const char * const dt_incompatible_devices[] = {
+	"LEN0304",
+	"LEN0306",
+	"LEN0317",
+	"LEN031A",
+	"LEN031B",
+	"LEN031C",
+	"LEN031D",
+};
+
+/*
+ * checks if it’s a doubletap capable device
+ * The PNP ID format eg: is "PNP: LEN030d PNP0f13".
+ */
+static bool is_trackpoint_dt_capable(const char *pnp_id)
+{
+	const char *id_start;
+	char id[8];
+
+	if (!strstarts(pnp_id, "PNP: LEN03"))
+		return false;
+
+	/* Points to "LEN03xxxx" */
+	id_start = pnp_id + 5;
+	if (sscanf(id_start, "%7s", id) != 1)
+		return false;
+
+	/* Check if it's blacklisted */
+	for (size_t i = 0; i < ARRAY_SIZE(dt_incompatible_devices); ++i) {
+		if (strcmp(id, dt_incompatible_devices[i]) == 0)
+			return false;
+	}
+	return true;
+}
+
+/* Trackpoint doubletap status function */
+static int trackpoint_doubletap_status(bool *status)
+{
+	struct trackpoint_data *tp = trackpoint_dev;
+	struct ps2dev *ps2dev = &tp->parent_psmouse->ps2dev;
+	u8 reg_val;
+	int rc;
+
+	/* Reading the Doubletap register using extended read */
+	rc = trackpoint_extended_read(ps2dev, TP_DOUBLETAP, &reg_val);
+	if (rc)
+		return rc;
+
+	*status = reg_val & TP_DOUBLETAP_STATUS ? true : false;
+
+	return 0;
+}
+
+/* Trackpoint doubletap enable/disable function */
+static int trackpoint_set_doubletap(bool enable)
+{
+	struct trackpoint_data *tp = trackpoint_dev;
+	struct ps2dev *ps2dev = &tp->parent_psmouse->ps2dev;
+	static u8 doubletap_state;
+	u8 new_val;
+
+	if (!tp)
+		return -ENODEV;
+
+	new_val = enable ? TP_DOUBLETAP_ENABLE : TP_DOUBLETAP_DISABLE;
+
+	if (doubletap_state == new_val)
+		return 0;
+
+	doubletap_state = new_val;
+
+	return trackpoint_write(ps2dev, TP_DOUBLETAP, new_val);
+}
+
+/*
+ * Trackpoint Doubletap Interface
+ * Control/Monitoring of Trackpoint Doubletap from:
+ * /sys/bus/serio/devices/seriox/doubletap_enabled
+ */
+static ssize_t doubletap_enabled_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct serio *serio = to_serio_port(dev);
+	struct psmouse *psmouse = psmouse_from_serio(serio);
+	struct trackpoint_data *tp = psmouse->private;
+	bool status;
+	int rc;
+
+	if (!tp || !tp->doubletap_capable)
+		return -ENODEV;
+
+	rc = trackpoint_doubletap_status(&status);
+	if (rc)
+		return rc;
+
+	return sysfs_emit(buf, "%d\n", status ? 1 : 0);
+}
+
+static ssize_t doubletap_enabled_store(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t count)
+{
+	struct serio *serio = to_serio_port(dev);
+	struct psmouse *psmouse = psmouse_from_serio(serio);
+	struct trackpoint_data *tp = psmouse->private;
+	bool enable;
+	int err;
+
+	if (!tp || !tp->doubletap_capable)
+		return -ENODEV;
+
+	err = kstrtobool(buf, &enable);
+	if (err)
+		return err;
+
+	err = trackpoint_set_doubletap(enable);
+	if (err)
+		return err;
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(doubletap_enabled);
+
 int trackpoint_detect(struct psmouse *psmouse, bool set_properties)
 {
 	struct ps2dev *ps2dev = &psmouse->ps2dev;
@@ -425,6 +567,9 @@ int trackpoint_detect(struct psmouse *psmouse, bool set_properties)
 	psmouse->reconnect = trackpoint_reconnect;
 	psmouse->disconnect = trackpoint_disconnect;
 
+	trackpoint_dev = psmouse->private;
+	trackpoint_dev->parent_psmouse = psmouse;
+
 	if (variant_id != TP_VARIANT_IBM) {
 		/* Newer variants do not support extended button query. */
 		button_info = 0x33;
@@ -470,6 +615,10 @@ int trackpoint_detect(struct psmouse *psmouse, bool set_properties)
 		     psmouse->vendor, firmware_id,
 		     (button_info & 0xf0) >> 4, button_info & 0x0f);
 
+	tp->doubletap_capable = is_trackpoint_dt_capable(ps2dev->serio->firmware_id);
+	if (tp->doubletap_capable)
+		device_create_file(&psmouse->ps2dev.serio->dev, &dev_attr_doubletap_enabled);
+
 	return 0;
 }
 
diff --git a/drivers/input/mouse/trackpoint.h b/drivers/input/mouse/trackpoint.h
index eb5412904fe0..256e8cb35581 100644
--- a/drivers/input/mouse/trackpoint.h
+++ b/drivers/input/mouse/trackpoint.h
@@ -8,6 +8,8 @@
 #ifndef _TRACKPOINT_H
 #define _TRACKPOINT_H
 
+#include <linux/bitops.h>
+
 /*
  * These constants are from the TrackPoint System
  * Engineering documentation Version 4 from IBM Watson
@@ -69,6 +71,8 @@
 					/* (how hard it is to drag */
 					/* with Z-axis pressed) */
 
+#define TP_DOUBLETAP		0x58	/* TrackPoint doubletap register */
+
 #define TP_MINDRAG		0x59	/* Minimum amount of force needed */
 					/* to trigger dragging */
 
@@ -139,6 +143,14 @@
 #define TP_DEF_TWOHAND		0x00
 #define TP_DEF_SOURCE_TAG	0x00
 
+/* Doubletap register values */
+#define TP_DOUBLETAP_ENABLE	0xFF	/* Enable value */
+#define TP_DOUBLETAP_DISABLE	0xFE	/* Disable value */
+
+#define TP_DOUBLETAP_STATUS_BIT 0	/* 0th bit defines enable/disable */
+
+#define TP_DOUBLETAP_STATUS   BIT(TP_DOUBLETAP_STATUS_BIT)
+
 #define MAKE_PS2_CMD(params, results, cmd) ((params<<12) | (results<<8) | (cmd))
 
 struct trackpoint_data {
@@ -150,11 +162,14 @@ struct trackpoint_data {
 	u8 thresh, upthresh;
 	u8 ztime, jenks;
 	u8 drift_time;
+	bool doubletap_capable;
 
 	/* toggles */
 	bool press_to_select;
 	bool skipback;
 	bool ext_dev;
+
+	struct psmouse *parent_psmouse;
 };
 
 int trackpoint_detect(struct psmouse *psmouse, bool set_properties);
-- 
2.48.1

[PATCH v3 2/3] Documentation/ABI: Add sysfs documentation for TrackPoint doubletap

[Vishnu Sankar]

Adding sysfs documentation for trackpoint doubletap.

Signed-off-by: Vishnu Sankar <vishnuocv@gmail.com>
---
Changes in v3:
- Add sysfs documentation.
---
 .../testing/sysfs-driver-trackpoint-doubletap   | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-driver-trackpoint-doubletap

diff --git a/Documentation/ABI/testing/sysfs-driver-trackpoint-doubletap b/Documentation/ABI/testing/sysfs-driver-trackpoint-doubletap
new file mode 100644
index 000000000000..d7cd63005523
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-trackpoint-doubletap
@@ -0,0 +1,17 @@
+What:          /sys/bus/serio/devices/serioX/doubletap_enabled
+Date:          Aug 2025
+KernelVersion: 6.17
+Contact:       linux-input@vger.kernel.org, platform-driver-x86@vger.kernel.org
+Description:
+               A read/write attribute controlling TrackPoint doubletap.
+
+               Reading returns the current state:
+               0 - disabled
+               1 - enabled
+
+               Writing:
+               0 - disable doubletap
+               1 - enable doubletap
+
+               The attribute is only present if the TrackPoint firmware
+               supports doubletap functionality.
-- 
2.48.1

[PATCH v3 3/3] platform/x86: thinkpad_acpi: Use trackpoint doubletap interface via sysfs

[Vishnu Sankar]

TrackPoint devices supporting doubletap expose a sysfs attribute under
/sys/devices/.../trackpoint/doubletap_enabled. This patch enables
thinkpad_acpi to detect if the system has a TrackPoint device with
doubletap capability, and allows toggling the feature via sysfs.

This avoids direct linking between subsystems and relies on sysfs
as the interface for coordination between input and platform drivers.

Signed-off-by: Vishnu Sankar <vishnuocv@gmail.com>
Suggested-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Suggested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
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
---
 drivers/platform/x86/lenovo/thinkpad_acpi.c | 155 +++++++++++++++++++-
 1 file changed, 147 insertions(+), 8 deletions(-)

diff --git a/drivers/platform/x86/lenovo/thinkpad_acpi.c b/drivers/platform/x86/lenovo/thinkpad_acpi.c
index cc19fe520ea9..f5070442a7ba 100644
--- a/drivers/platform/x86/lenovo/thinkpad_acpi.c
+++ b/drivers/platform/x86/lenovo/thinkpad_acpi.c
@@ -72,6 +72,13 @@
 #include <linux/units.h>
 #include <linux/workqueue.h>
 
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/err.h>
+#include <linux/fcntl.h>
+#include <linux/namei.h>
+#include <linux/kernel_read_file.h>
+
 #include <acpi/battery.h>
 #include <acpi/video.h>
 
@@ -373,7 +380,8 @@ static struct {
 	u32 hotkey_poll_active:1;
 	u32 has_adaptive_kbd:1;
 	u32 kbd_lang:1;
-	u32 trackpoint_doubletap:1;
+	u32 trackpoint_doubletap_state:1;
+	u32 trackpoint_doubletap_capable:1;
 	struct quirk_entry *quirks;
 } tp_features;
 
@@ -2879,6 +2887,107 @@ static DEVICE_ATTR_RW(hotkey_poll_freq);
 
 #endif /* CONFIG_THINKPAD_ACPI_HOTKEY_POLL */
 
+/*
+ * Trackpoint doubletap handlers
+ * These set of functions will communicate with the sysfs attributes of TrackPoint driver
+ * Attribute : /sys/bus/serio/devices/seriox/doubletap_enabled
+ */
+
+/* Global buffer to reuse path */
+static char trackpoint_doubletap_path[128];
+
+/* Function to find the correct serio path with TrackPoint attribute "doubletap_enabled" */
+static int thinkpad_find_trackpoint_path(void)
+{
+	struct path serio_path;
+	char path_buf[128];
+	int i;
+
+	for (i = 0; i < 10; i++) {
+		snprintf(path_buf, sizeof(path_buf),
+		"/sys/bus/serio/devices/serio%d/doubletap_enabled", i);
+
+		if (!kern_path(path_buf, LOOKUP_FOLLOW, &serio_path)) {
+			path_put(&serio_path);
+			snprintf(trackpoint_doubletap_path, sizeof(trackpoint_doubletap_path),
+				"%s", path_buf);
+			pr_info("ThinkPad ACPI: TrackPoint doubletap found at %s\n",
+				trackpoint_doubletap_path);
+			return 0;
+		}
+	}
+	return -ENODEV;
+}
+
+/* Writing to the sysfs attribute of Trackpoint "doubletap_enabled" */
+static int write_doubletap_sysfs_value(const void *buf, size_t count, loff_t *pos)
+{
+	struct file *filp;
+	ssize_t written;
+
+	if (!buf)
+		return -EINVAL;
+
+	filp = filp_open(trackpoint_doubletap_path, O_WRONLY | O_CREAT, 0644);
+	if (IS_ERR(filp))
+		return PTR_ERR(filp);
+
+	/* Required to avoid EINVAL from vfs checks in some cases */
+	if (!(filp->f_mode & FMODE_CAN_WRITE)) {
+		filp_close(filp, NULL);
+		return -EINVAL;
+	}
+
+	/* Write using kernel_write */
+	written = kernel_write(filp, buf, count, pos);
+	filp_close(filp, NULL);
+
+	return written < 0 ? written : 0;
+}
+
+/* Function to read the TrackPoint doubletap status */
+static int trackpoint_read_doubletap_status(bool *enabled)
+{
+	struct file *filp;
+	loff_t pos = 0;
+	char buf[8];
+	ssize_t ret;
+
+	if (!enabled)
+		return -EINVAL;
+
+	if (!trackpoint_doubletap_path[0])
+		return -ENODEV;
+
+	filp = filp_open(trackpoint_doubletap_path, O_RDONLY, 0);
+	if (IS_ERR(filp))
+		return PTR_ERR(filp);
+
+	ret = kernel_read(filp, buf, sizeof(buf) - 1, &pos);
+	filp_close(filp, NULL);
+
+	if (ret < 0)
+		return ret;
+
+	buf[ret] = '\0'; // Safe: ret < sizeof(buf)
+
+	*enabled = (buf[0] == '1');
+
+	return 0;
+}
+
+/* Function to check the TrackPoint doubletap status */
+static int thinkpad_set_doubletap_status(bool enable)
+{
+	const char *val = enable ? "1" : "0";
+	loff_t pos = 0;
+
+	if (!trackpoint_doubletap_path[0])
+		return -ENODEV;
+
+	return write_doubletap_sysfs_value(val, strlen(val), &pos);
+}
+
 /* sysfs hotkey radio_sw (pollable) ------------------------------------ */
 static ssize_t hotkey_radio_sw_show(struct device *dev,
 			   struct device_attribute *attr,
@@ -3326,6 +3435,8 @@ static int __init hotkey_init(struct ibm_init_struct *iibm)
 	bool radiosw_state  = false;
 	bool tabletsw_state = false;
 	int hkeyv, res, status, camera_shutter_state;
+	bool dt_state;
+	int rc;
 
 	vdbg_printk(TPACPI_DBG_INIT | TPACPI_DBG_HKEY,
 			"initializing hotkey subdriver\n");
@@ -3557,9 +3668,22 @@ static int __init hotkey_init(struct ibm_init_struct *iibm)
 
 	hotkey_poll_setup_safe(true);
 
-	/* Enable doubletap by default */
-	tp_features.trackpoint_doubletap = 1;
+	/* Checking doubletap status by default */
+	rc = thinkpad_find_trackpoint_path();
+	if (rc) {
+		dev_dbg(&tpacpi_pdev->dev, "Could not find TrackPoint doubletap sysfs path\n");
+		tp_features.trackpoint_doubletap_capable = false;
+		return 0;
+	}
+	tp_features.trackpoint_doubletap_capable = true;
 
+	rc = trackpoint_read_doubletap_status(&dt_state);
+	if (rc) {
+		/* Disable if access to register fails */
+		dt_state = false;
+		dev_dbg(&tpacpi_pdev->dev, "Doubletap failed to check status\n");
+	}
+	tp_features.trackpoint_doubletap_state = dt_state;
 	return 0;
 }
 
@@ -3863,9 +3987,7 @@ 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);
-
+		*send_acpi_ev = true;
 		return true;
 	default:
 		return false;
@@ -11194,6 +11316,7 @@ static struct platform_driver tpacpi_hwmon_pdriver = {
 static bool tpacpi_driver_event(const unsigned int hkey_event)
 {
 	int camera_shutter_state;
+	int rc;
 
 	switch (hkey_event) {
 	case TP_HKEY_EV_BRGHT_UP:
@@ -11285,8 +11408,24 @@ 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;
-		return true;
+		if (tp_features.trackpoint_doubletap_capable) {
+			rc = thinkpad_set_doubletap_status(!tp_features.trackpoint_doubletap_state);
+
+			if (rc) {
+				dev_dbg(&tpacpi_pdev->dev, "Trackpoint doubletap toggle failed\n");
+			} else {
+				tp_features.trackpoint_doubletap_state =
+					!tp_features.trackpoint_doubletap_state;
+				dev_dbg(&tpacpi_pdev->dev, "Trackpoint doubletap is %s\n",
+						tp_features.trackpoint_doubletap_state ? "enabled" : "disabled");
+				return true;
+			}
+		}
+		/*
+		 * Suppress the event if Doubletap is not supported
+		 * or if the trackpoint_set_doubletap_status() is failing
+		 */
+		return false;
 	case TP_HKEY_EV_PROFILE_TOGGLE:
 	case TP_HKEY_EV_PROFILE_TOGGLE2:
 		platform_profile_cycle();
-- 
2.48.1