The Windows Precision Touchpad spec "Figure 4 Button Only Down and Up"
and "Table 9 Report Sequence for Button Only Down and Up" indicate
that the first packet of a (possibly hybrid mode multi-packet) frame
may contain a contact-count of 0 if only a button is pressed and no
fingers are detected.
This means that a value of 0 for contact-count is a valid value and
should be used as expected contact count when it is the first packet
(num_received == 0), as extra check to make sure that this is the first
packet of a buttons only frame, we also check that the timestamp is
different.
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
---
Changes in v2:
-New patch in v2 of this patch-set
Changes in v3:
-Also check timestamps to make sure we're dealing with the first-packet
of a frame
Changes in v4:
-Add Benjamin's Reviewed-by
---
drivers/hid/hid-multitouch.c | 34 ++++++++++++++++++++++++++++++++--
include/linux/hid.h | 1 +
2 files changed, 33 insertions(+), 2 deletions(-)
diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index bb939f6990f1..5d3904d0e89d 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -117,6 +117,9 @@ struct mt_device {
unsigned long mt_io_flags; /* mt flags (MT_IO_FLAGS_*) */
int cc_index; /* contact count field index in the report */
int cc_value_index; /* contact count value index in the field */
+ int scantime_index; /* scantime field index in the report */
+ int scantime_val_index; /* scantime value index in the field */
+ int prev_scantime; /* scantime reported in the previous packet */
unsigned last_slot_field; /* the last field of a slot */
unsigned mt_report_id; /* the report ID of the multitouch device */
unsigned long initial_quirks; /* initial quirks state */
@@ -595,6 +598,14 @@ static int mt_touch_input_mapping(struct hid_device *hdev, struct hid_input *hi,
/* we don't set td->last_slot_field as contactcount and
* contact max are global to the report */
return -1;
+ case HID_DG_SCANTIME:
+ /* Ignore if indexes are out of bounds. */
+ if (field->index >= field->report->maxfield ||
+ usage->usage_index >= field->report_count)
+ return 1;
+ td->scantime_index = field->index;
+ td->scantime_val_index = usage->usage_index;
+ return 1;
case HID_DG_TOUCH:
/* Legacy devices use TIPSWITCH and not TOUCH.
* Let's just ignore this field. */
@@ -812,9 +823,10 @@ static void mt_process_mt_event(struct hid_device *hid, struct hid_field *field,
static void mt_touch_report(struct hid_device *hid, struct hid_report *report)
{
struct mt_device *td = hid_get_drvdata(hid);
+ __s32 cls = td->mtclass.name;
struct hid_field *field;
unsigned count;
- int r, n;
+ int r, n, scantime = 0;
/* sticky fingers release in progress, abort */
if (test_and_set_bit(MT_IO_FLAGS_RUNNING, &td->mt_io_flags))
@@ -824,12 +836,29 @@ static void mt_touch_report(struct hid_device *hid, struct hid_report *report)
* Includes multi-packet support where subsequent
* packets are sent with zero contactcount.
*/
+ if (td->scantime_index >= 0) {
+ field = report->field[td->scantime_index];
+ scantime = field->value[td->scantime_val_index];
+ }
if (td->cc_index >= 0) {
struct hid_field *field = report->field[td->cc_index];
int value = field->value[td->cc_value_index];
- if (value)
+
+ /*
+ * For Win8 PTPs the first packet (td->num_received == 0) may
+ * have a contactcount of 0 if there only is a button event.
+ * We double check that this is not a continuation packet
+ * of a possible multi-packet frame be checking that the
+ * timestamp has changed.
+ */
+ if ((cls == MT_CLS_WIN_8 || cls == MT_CLS_WIN_8_DUAL) &&
+ td->num_received == 0 && td->prev_scantime != scantime)
+ td->num_expected = value;
+ /* A non 0 contact count always indicates a first packet */
+ else if (value)
td->num_expected = value;
}
+ td->prev_scantime = scantime;
for (r = 0; r < report->maxfield; r++) {
field = report->field[r];
@@ -1285,6 +1314,7 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
td->maxcontact_report_id = -1;
td->inputmode_value = MT_INPUTMODE_TOUCHSCREEN;
td->cc_index = -1;
+ td->scantime_index = -1;
td->mt_report_id = -1;
hid_set_drvdata(hdev, td);
diff --git a/include/linux/hid.h b/include/linux/hid.h
index ab05a86269dc..47dd962d9a7a 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -289,6 +289,7 @@ struct hid_item {
#define HID_DG_DEVICEINDEX 0x000d0053
#define HID_DG_CONTACTCOUNT 0x000d0054
#define HID_DG_CONTACTMAX 0x000d0055
+#define HID_DG_SCANTIME 0x000d0056
#define HID_DG_BUTTONTYPE 0x000d0059
#define HID_DG_BARRELSWITCH2 0x000d005a
#define HID_DG_TOOLSERIALNUMBER 0x000d005b
--
2.14.3
--
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