[PATCH v4 14/14] HID: hid-multitouch: forwards MSC_TIMESTAMP

[Benjamin Tissoires]

Computes the device timestamp according to the specification.
It also ensures that if the time between two events is greater
than MAX_TIMESTAMP_INTERVAL, the timestamp will be reset.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxx>
---
 drivers/hid/hid-multitouch.c | 46 +++++++++++++++++++++++++++++++++++++++++---
 include/linux/hid.h          |  1 +
 2 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index efae60c..47ccf3a 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -32,6 +32,7 @@
 #include <linux/slab.h>
 #include <linux/usb.h>
 #include <linux/input/mt.h>
+#include <linux/jiffies.h>
 #include "usbhid/usbhid.h"
 
 
@@ -98,6 +99,9 @@ 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 */
+	__s32 dev_time;		/* the scan time provided by the device */
+	unsigned long jiffies;	/* the frame's jiffies */
+	unsigned timestamp;	/* the timestamp to be sent */
 };
 
 /* classes of device behavior */
@@ -126,6 +130,8 @@ struct mt_device {
 #define MT_DEFAULT_MAXCONTACT	10
 #define MT_MAX_MAXCONTACT	250
 
+#define MAX_TIMESTAMP_INTERVAL	500000
+
 #define MT_USB_DEVICE(v, p)	HID_DEVICE(BUS_USB, HID_GROUP_MULTITOUCH, v, p)
 #define MT_BT_DEVICE(v, p)	HID_DEVICE(BUS_BLUETOOTH, HID_GROUP_MULTITOUCH, v, p)
 
@@ -459,12 +465,19 @@ 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;
 		}
@@ -493,7 +506,8 @@ 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;
@@ -572,10 +586,33 @@ 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,
+		__s32 value)
+{
+	long delta = value - td->dev_time;
+	unsigned long jdelta = jiffies_to_usecs(jiffies - td->jiffies);
+
+	td->jiffies = jiffies;
+	td->dev_time = value;
+
+	if (delta < 0)
+		delta += field->logical_maximum;
+
+	/* HID_DG_SCANTIME is expressed in 100us, we want it in ms. */
+	delta *= 100;
+
+	if (abs(delta - jdelta) > MAX_TIMESTAMP_INTERVAL)
+		/* obviously wrong clock -> the device time has been reset */
+		td->timestamp = 0;
+	else
+		td->timestamp += delta;
+}
+
 static int mt_event(struct hid_device *hid, struct hid_field *field,
 				struct hid_usage *usage, __s32 value)
 {
@@ -623,6 +660,9 @@ 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 ce14c32..aaba0e7 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -279,6 +279,7 @@ 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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