[PATCH v3 13/13] HID: hid-multitouch: forwards ABS_SCAN_TIME

[Benjamin Tissoires <benjamin.tissoires@gmail.com>]

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

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
---
 drivers/hid/hid-multitouch.c | 45 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 43 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 1f3d1e0..5902567 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 scan_time;	/* the scan time to be sent */
 };
 
 /* classes of device behavior */
@@ -126,6 +130,9 @@ struct mt_device {
 #define MT_DEFAULT_MAXCONTACT	10
 #define MT_MAX_MAXCONTACT	250
 
+#define MAX_SCAN_TIME		INT_MAX
+#define MAX_SCAN_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)
 
@@ -451,12 +458,20 @@ 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_ABS, ABS_SCAN_TIME);
+			input_set_abs_params(hi->input,
+				ABS_SCAN_TIME, 0, MAX_SCAN_TIME, 0, 0);
+			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;
 		}
@@ -565,11 +580,34 @@ 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_event(input, EV_ABS, ABS_SCAN_TIME, td->scan_time);
 	input_mt_sync_frame(input);
 	input_sync(input);
 	td->num_received = 0;
 }
 
+static void mt_compute_scan_time(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_SCAN_INTERVAL)
+		/* obviously wrong clock -> the device time has been reset */
+		td->scan_time = 0;
+	else
+		td->scan_time += delta;
+}
+
 static int mt_event(struct hid_device *hid, struct hid_field *field,
 				struct hid_usage *usage, __s32 value)
 {
@@ -617,6 +655,9 @@ 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_scan_time(td, field, value);
+			break;
 		case HID_DG_CONTACTCOUNT:
 			/*
 			 * Includes multi-packet support where subsequent
-- 
1.7.11.7