Computes and forwards the device timestamp according to the
specification.
Many devices use a 16-bit timestamp field, with a resolution
of 100us, therefore rolling around very frequently (every
6.5 seconds). To make sure there is no ambiguity, the
timestamp reported to the input stack reset to 0 whenever
the time between 2 received events is greater than
MAX_TIMESTAMP_INTERVAL (1 second).
Signed-off-by: Nicolas Boichat <[email protected]>
---
Inspired from Benjamin Tissoires's patch here:
https://patchwork.kernel.org/patch/1742181/, and changing the
logic to resynchronize the timestamps to use received time
instead of a potentially more fragile difference between
the 2 deltas.
drivers/hid/hid-multitouch.c | 42 ++++++++++++++++++++++++++++++++++++++++++
include/linux/hid.h | 1 +
2 files changed, 43 insertions(+)
diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 440b999304a5..996bdc9bf0e5 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -43,6 +43,7 @@
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/input/mt.h>
+#include <linux/jiffies.h>
#include <linux/string.h>
#include <linux/timer.h>
@@ -136,6 +137,9 @@ 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 */
+ int timestamp; /* the timestamp to be sent */
};
static void mt_post_parse_default_settings(struct mt_device *td);
@@ -177,6 +181,12 @@ static void mt_post_parse(struct mt_device *td);
#define MT_DEFAULT_MAXCONTACT 10
#define MT_MAX_MAXCONTACT 250
+/*
+ * Resync device and local timestamps after that many microseconds without
+ * receiving data.
+ */
+#define MAX_TIMESTAMP_INTERVAL 1000000
+
#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)
@@ -583,6 +593,12 @@ static int mt_touch_input_mapping(struct hid_device *hdev, struct hid_input *hi,
cls->sn_pressure);
mt_store_field(usage, td, hi);
return 1;
+ case HID_DG_SCANTIME:
+ hid_map_usage(hi, usage, bit, max,
+ EV_MSC, MSC_TIMESTAMP);
+ input_set_capability(hi->input, EV_MSC, MSC_TIMESTAMP);
+ mt_store_field(usage, td, hi);
+ return 1;
case HID_DG_CONTACTCOUNT:
/* Ignore if indexes are out of bounds. */
if (field->index >= field->report->maxfield ||
@@ -718,6 +734,7 @@ 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;
if (test_bit(MT_IO_FLAGS_ACTIVE_SLOTS, &td->mt_io_flags))
@@ -727,6 +744,28 @@ static void mt_sync_frame(struct mt_device *td, struct input_dev *input)
clear_bit(MT_IO_FLAGS_ACTIVE_SLOTS, &td->mt_io_flags);
}
+static int 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 us. */
+ delta *= 100;
+
+ if (jdelta > MAX_TIMESTAMP_INTERVAL)
+ /* No data received for a while, resync the timestamp. */
+ return 0;
+ else
+ return td->timestamp + delta;
+}
+
static int mt_touch_event(struct hid_device *hid, struct hid_field *field,
struct hid_usage *usage, __s32 value)
{
@@ -787,6 +826,9 @@ static void mt_process_mt_event(struct hid_device *hid, struct hid_field *field,
case HID_DG_HEIGHT:
td->curdata.h = value;
break;
+ case HID_DG_SCANTIME:
+ td->timestamp = mt_compute_timestamp(td, field, value);
+ break;
case HID_DG_CONTACTCOUNT:
break;
case HID_DG_TOUCH:
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
--
2.14.1.480.gb18f417b89-goog