FAILED: patch "[PATCH] HID: multitouch: fix sticky fingers" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 46f781e0d151844589dc2125c8cce3300546f92a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025102010-botch-underling-438f@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 46f781e0d151844589dc2125c8cce3300546f92a Mon Sep 17 00:00:00 2001
From: Benjamin Tissoires <bentiss@kernel.org>
Date: Wed, 8 Oct 2025 16:06:58 +0200
Subject: [PATCH] HID: multitouch: fix sticky fingers

The sticky fingers quirk (MT_QUIRK_STICKY_FINGERS) was only considering
the case when slots were not released during the last report.
This can be problematic if the firmware forgets to release a finger
while others are still present.

This was observed on the Synaptics DLL0945 touchpad found on the Dell
XPS 9310 and the Dell Inspiron 5406.

Fixes: 4f4001bc76fd ("HID: multitouch: fix rare Win 8 cases when the touch up event gets missing")
Cc: stable@vger.kernel.org
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 513b8673ad8d..179dc316b4b5 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -94,9 +94,8 @@ enum report_mode {
 	TOUCHPAD_REPORT_ALL = TOUCHPAD_REPORT_BUTTONS | TOUCHPAD_REPORT_CONTACTS,
 };
 
-#define MT_IO_FLAGS_RUNNING		0
-#define MT_IO_FLAGS_ACTIVE_SLOTS	1
-#define MT_IO_FLAGS_PENDING_SLOTS	2
+#define MT_IO_SLOTS_MASK		GENMASK(7, 0) /* reserve first 8 bits for slot tracking */
+#define MT_IO_FLAGS_RUNNING		32
 
 static const bool mtrue = true;		/* default for true */
 static const bool mfalse;		/* default for false */
@@ -172,7 +171,11 @@ struct mt_device {
 	struct timer_list release_timer;	/* to release sticky fingers */
 	struct hid_haptic_device *haptic;	/* haptic related configuration */
 	struct hid_device *hdev;	/* hid_device we're attached to */
-	unsigned long mt_io_flags;	/* mt flags (MT_IO_FLAGS_*) */
+	unsigned long mt_io_flags;	/* mt flags (MT_IO_FLAGS_RUNNING)
+					 * first 8 bits are reserved for keeping the slot
+					 * states, this is fine because we only support up
+					 * to 250 slots (MT_MAX_MAXCONTACT)
+					 */
 	__u8 inputmode_value;	/* InputMode HID feature value */
 	__u8 maxcontacts;
 	bool is_buttonpad;	/* is this device a button pad? */
@@ -986,6 +989,7 @@ static void mt_release_pending_palms(struct mt_device *td,
 
 	for_each_set_bit(slotnum, app->pending_palm_slots, td->maxcontacts) {
 		clear_bit(slotnum, app->pending_palm_slots);
+		clear_bit(slotnum, &td->mt_io_flags);
 
 		input_mt_slot(input, slotnum);
 		input_mt_report_slot_inactive(input);
@@ -1019,12 +1023,6 @@ static void mt_sync_frame(struct mt_device *td, struct mt_application *app,
 	app->left_button_state = 0;
 	if (td->is_haptic_touchpad)
 		hid_haptic_pressure_reset(td->haptic);
-
-	if (test_bit(MT_IO_FLAGS_ACTIVE_SLOTS, &td->mt_io_flags))
-		set_bit(MT_IO_FLAGS_PENDING_SLOTS, &td->mt_io_flags);
-	else
-		clear_bit(MT_IO_FLAGS_PENDING_SLOTS, &td->mt_io_flags);
-	clear_bit(MT_IO_FLAGS_ACTIVE_SLOTS, &td->mt_io_flags);
 }
 
 static int mt_compute_timestamp(struct mt_application *app, __s32 value)
@@ -1202,7 +1200,9 @@ static int mt_process_slot(struct mt_device *td, struct input_dev *input,
 		input_event(input, EV_ABS, ABS_MT_TOUCH_MAJOR, major);
 		input_event(input, EV_ABS, ABS_MT_TOUCH_MINOR, minor);
 
-		set_bit(MT_IO_FLAGS_ACTIVE_SLOTS, &td->mt_io_flags);
+		set_bit(slotnum, &td->mt_io_flags);
+	} else {
+		clear_bit(slotnum, &td->mt_io_flags);
 	}
 
 	return 0;
@@ -1337,7 +1337,7 @@ static void mt_touch_report(struct hid_device *hid,
 	 * defect.
 	 */
 	if (app->quirks & MT_QUIRK_STICKY_FINGERS) {
-		if (test_bit(MT_IO_FLAGS_PENDING_SLOTS, &td->mt_io_flags))
+		if (td->mt_io_flags & MT_IO_SLOTS_MASK)
 			mod_timer(&td->release_timer,
 				  jiffies + msecs_to_jiffies(100));
 		else
@@ -1814,6 +1814,7 @@ static void mt_release_contacts(struct hid_device *hid)
 			for (i = 0; i < mt->num_slots; i++) {
 				input_mt_slot(input_dev, i);
 				input_mt_report_slot_inactive(input_dev);
+				clear_bit(i, &td->mt_io_flags);
 			}
 			input_mt_sync_frame(input_dev);
 			input_sync(input_dev);
@@ -1836,7 +1837,7 @@ static void mt_expired_timeout(struct timer_list *t)
 	 */
 	if (test_and_set_bit_lock(MT_IO_FLAGS_RUNNING, &td->mt_io_flags))
 		return;
-	if (test_bit(MT_IO_FLAGS_PENDING_SLOTS, &td->mt_io_flags))
+	if (td->mt_io_flags & MT_IO_SLOTS_MASK)
 		mt_release_contacts(hdev);
 	clear_bit_unlock(MT_IO_FLAGS_RUNNING, &td->mt_io_flags);
 }