[PATCH] HID: hid-multitouch: send the device timestamp when present

[Henrik Rydberg]

Compute and relay the device timestamp when present. The counter
value range varies between devices, but the MSC_TIMESTAMP event
is always 32 bits long. A value of zero means the time since the
previous event is unknown.

Signed-off-by: Henrik Rydberg <rydberg@xxxxxxxxxxx>
---
 drivers/hid/hid-multitouch.c | 36 +++++++++++++++++++++++++++++++++---
 include/linux/hid.h          |  1 +
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 61543c0..586f9c6 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -98,6 +98,8 @@ struct mt_device {
 	bool serial_maybe;	/* need to check for serial protocol */
 	bool curvalid;		/* is the current contact valid? */
 	unsigned mt_flags;	/* flags to pass to input-mt */
+	unsigned dev_time;	/* device scan time in units of 100 us */
+	unsigned timestamp;	/* the timestamp to be sent */
 };
 
 /* classes of device behavior */
@@ -458,12 +460,19 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 			mt_store_field(usage, td, hi);
 			td->last_field_index = field->index;
 			return 1;
+		case HID_DG_SCANTIME:
+			hid_map_usage(hi, usage, bit, max,
+				EV_MSC, MSC_TIMESTAMP);
+			set_bit(MSC_TIMESTAMP, hi->input->mscbit);
+			td->last_field_index = field->index;
+			return 1;
 		case HID_DG_CONTACTCOUNT:
 			td->last_field_index = field->index;
 			return 1;
 		case HID_DG_CONTACTMAX:
-			/* we don't set td->last_slot_field as contactcount and
-			 * contact max are global to the report */
+			/* we don't set td->last_slot_field as scan time,
+			 * contactcount and contact max are global to the
+			 * report */
 			td->last_field_index = field->index;
 			return -1;
 		case HID_DG_TOUCH:
@@ -492,7 +501,8 @@ static int mt_input_mapped(struct hid_device *hdev, struct hid_input *hi,
 		struct hid_field *field, struct hid_usage *usage,
 		unsigned long **bit, int *max)
 {
-	if (usage->type == EV_KEY || usage->type == EV_ABS)
+	if (usage->type == EV_KEY || usage->type == EV_ABS ||
+	    usage->type == EV_MSC)
 		set_bit(usage->type, hi->input->evbit);
 
 	return -1;
@@ -571,10 +581,27 @@ static void mt_complete_slot(struct mt_device *td, struct input_dev *input)
 static void mt_sync_frame(struct mt_device *td, struct input_dev *input)
 {
 	input_mt_sync_frame(input);
+	input_event(input, EV_MSC, MSC_TIMESTAMP, td->timestamp);
 	input_sync(input);
 	td->num_received = 0;
 }
 
+static void mt_compute_timestamp(struct mt_device *td, struct hid_field *field,
+				 unsigned value)
+{
+	unsigned dt;
+
+	if (value) {
+		dt = (value - td->dev_time) % (field->logical_maximum + 1);
+		td->timestamp += 100 * dt;
+		td->timestamp += !td->timestamp;
+	} else {
+		td->timestamp = 0;
+	}
+
+	td->dev_time = value;
+}
+
 static int mt_event(struct hid_device *hid, struct hid_field *field,
 				struct hid_usage *usage, __s32 value)
 {
@@ -622,6 +649,9 @@ static int mt_event(struct hid_device *hid, struct hid_field *field,
 		case HID_DG_HEIGHT:
 			td->curdata.h = value;
 			break;
+		case HID_DG_SCANTIME:
+			mt_compute_timestamp(td, field, value);
+			break;
 		case HID_DG_CONTACTCOUNT:
 			/*
 			 * Includes multi-packet support where subsequent
diff --git a/include/linux/hid.h b/include/linux/hid.h
index d2c42dd..eb7ec6c 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -242,6 +242,7 @@ struct hid_item {
 #define HID_DG_DEVICEINDEX	0x000d0053
 #define HID_DG_CONTACTCOUNT	0x000d0054
 #define HID_DG_CONTACTMAX	0x000d0055
+#define HID_DG_SCANTIME		0x000d0056
 
 /*
  * HID report types --- Ouch! HID spec says 1 2 3!
-- 
1.8.0

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