[PATCH 4.15 030/128] HID: multitouch: Only look at non touch fields in first packet of a frame

Greg Kroah-Hartman
2018-03-16T15:40:25Z

From: Hans de Goede <hdegoede@redhat.com>

[ Upstream commit 55746d28d66860bccaae20a67b55b9d5db7c14af ]

Devices in "single finger hybrid mode" will send one report per finger,
on some devices only the first report of such a multi-packet frame will
contain a value for BTN_LEFT, in subsequent reports (if multiple fingers
are down) the value is always 0, causing hid-mt to report BTN_LEFT going
1 - 0 - 1 - 0 when pressing a clickpad and putting down a second finger.
This happens for example on USB 0603:0002 mt touchpads.

This commit fixes this by only reporting non touch fields for the first
packet of a (possibly) multi-packet frame.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/hid/hid-multitouch.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 65ea23be9677..397592959238 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -778,9 +778,11 @@ static int mt_touch_event(struct hid_device *hid, struct hid_field *field,
}

static void mt_process_mt_event(struct hid_device *hid, struct hid_field *field,
- struct hid_usage *usage, __s32 value)
+ struct hid_usage *usage, __s32 value,
+ bool first_packet)
{
struct mt_device *td = hid_get_drvdata(hid);
+ __s32 cls = td->mtclass.name;
__s32 quirks = td->mtclass.quirks;
struct input_dev *input = field->hidinput->input;

@@ -837,6 +839,15 @@ static void mt_process_mt_event(struct hid_device *hid, struct hid_field *field,
break;

default:
+ /*
+ * For Win8 PTP touchpads we should only look at
+ * non finger/touch events in the first_packet of
+ * a (possible) multi-packet frame.
+ */
+ if ((cls == MT_CLS_WIN_8 || cls == MT_CLS_WIN_8_DUAL) &&
+ !first_packet)
+ return;
+
if (usage->type)
input_event(input, usage->type, usage->code,
value);
@@ -856,6 +867,7 @@ static void mt_touch_report(struct hid_device *hid, struct hid_report *report)
{
struct mt_device *td = hid_get_drvdata(hid);
struct hid_field *field;
+ bool first_packet;
unsigned count;
int r, n;

@@ -874,6 +886,7 @@ static void mt_touch_report(struct hid_device *hid, struct hid_report *report)
td->num_expected = value;
}

+ first_packet = td->num_received == 0;
for (r = 0; r < report->maxfield; r++) {
field = report->field[r];
count = field->report_count;
@@ -883,7 +896,7 @@ static void mt_touch_report(struct hid_device *hid, struct hid_report *report)

for (n = 0; n < count; n++)
mt_process_mt_event(hid, field, &field->usage[n],
- field->value[n]);
+ field->value[n], first_packet);
}

if (td->num_received >= td->num_expected)
--
2.16.2