HID: multitouch: enable palm rejection for Windows Precision Touchpad

The usage Confidence is mandary to Windows Precision Touchpad devices. If
it is examined in input_mapping on a WIndows Precision Touchpad, a new add
quirk MT_QUIRK_CONFIDENCE desgned for such devices will be applied to the
device. A touch with the confidence bit is not set is determined as
invalid.

Tested on Dell XPS13 9343

Cc: stable@vger.kernel.org # v4.5+
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Tested-by: Andy Lutomirski <luto@kernel.org> # XPS 13 9350, BIOS 1.4.3
Signed-off-by: Allen Hung <allen_hung@dell.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 15 insertions, 3 deletions

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 4ef700688657..fb6f1f447279 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -61,6 +61,7 @@ MODULE_LICENSE("GPL");
 #define MT_QUIRK_ALWAYS_VALID           (1 << 4)
 #define MT_QUIRK_VALID_IS_INRANGE       (1 << 5)
 #define MT_QUIRK_VALID_IS_CONFIDENCE    (1 << 6)
+#define MT_QUIRK_CONFIDENCE             (1 << 7)
 #define MT_QUIRK_SLOT_IS_CONTACTID_MINUS_ONE    (1 << 8)
 #define MT_QUIRK_NO_AREA                (1 << 9)
 #define MT_QUIRK_IGNORE_DUPLICATES      (1 << 10)
@@ -78,6 +79,7 @@ struct mt_slot {
         __s32 contactid;        /* the device ContactID assigned to this slot */
         bool touch_state;       /* is the touch valid? */
         bool inrange_state;     /* is the finger in proximity of the sensor? */
+        bool confidence_state;  /* is the touch made by a finger? */
 };
 
 struct mt_class {
@@ -502,6 +504,9 @@ static int mt_touch_input_mapping(struct hid_device *hdev, struct hid_input *hi,
                         mt_store_field(usage, td, hi);
                         return 1;
                 case HID_DG_CONFIDENCE:
+                        if (cls->name == MT_CLS_WIN_8 &&
+                                field->application == HID_DG_TOUCHPAD)
+                                cls->quirks |= MT_QUIRK_CONFIDENCE;
                         mt_store_field(usage, td, hi);
                         return 1;
                 case HID_DG_TIPSWITCH:
@@ -614,6 +619,7 @@ static void mt_complete_slot(struct mt_device *td, struct input_dev *input)
                 return;
 
         if (td->curvalid || (td->mtclass.quirks & MT_QUIRK_ALWAYS_VALID)) {
+                int active;
                 int slotnum = mt_compute_slot(td, input);
                 struct mt_slot *s = &td->curdata;
                 struct input_mt *mt = input->mt;
@@ -628,10 +634,14 @@ static void mt_complete_slot(struct mt_device *td, struct input_dev *input)
                                 return;
                 }
 
+                if (!(td->mtclass.quirks & MT_QUIRK_CONFIDENCE))
+                        s->confidence_state = 1;
+                active = (s->touch_state || s->inrange_state) &&
+                                                        s->confidence_state;
+
                 input_mt_slot(input, slotnum);
-                input_mt_report_slot_state(input, MT_TOOL_FINGER,
-                        s->touch_state || s->inrange_state);
-                if (s->touch_state || s->inrange_state) {
+                input_mt_report_slot_state(input, MT_TOOL_FINGER, active);
+                if (active) {
                         /* this finger is in proximity of the sensor */
                         int wide = (s->w > s->h);
                         /* divided by two to match visual scale of touch */
@@ -696,6 +706,8 @@ static void mt_process_mt_event(struct hid_device *hid, struct hid_field *field,
                         td->curdata.touch_state = value;
                         break;
                 case HID_DG_CONFIDENCE:
+                        if (quirks & MT_QUIRK_CONFIDENCE)
+                                td->curdata.confidence_state = value;
                         if (quirks & MT_QUIRK_VALID_IS_CONFIDENCE)
                                 td->curvalid = value;
                         break;