HID: hid-multitouch: forward MSC_TIMESTAMP
authorNicolas Boichat <drinkcat@chromium.org>
Tue, 22 Aug 2017 01:10:11 +0000 (09:10 +0800)
committerJiri Kosina <jkosina@suse.cz>
Thu, 5 Oct 2017 09:18:18 +0000 (11:18 +0200)
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 <drinkcat@chromium.org>
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
drivers/hid/hid-multitouch.c
include/linux/hid.h

index 440b999..996bdc9 100644 (file)
@@ -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:
index ab05a86..47dd962 100644 (file)
@@ -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