Input: allow drivers specify timestamp for input events

Currently, evdev stamps events with timestamps acquired in evdev_events()
However, this timestamping may not be accurate in terms of measuring
when the actual event happened.

Let's allow individual drivers specify timestamp in order to provide a more
accurate sense of time for the event. It is expected that drivers will set the
timestamp in their hard interrupt routine.

Signed-off-by: Atif Niyaz <atifniyaz@google.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/drivers/input/input.c b/drivers/input/input.c
index 7f3c5fcb9ed6..7494a0dede79 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -1895,6 +1895,46 @@ void input_free_device(struct input_dev *dev)
 EXPORT_SYMBOL(input_free_device);
 
 /**
+ * input_set_timestamp - set timestamp for input events
+ * @dev: input device to set timestamp for
+ * @timestamp: the time at which the event has occurred
+ *   in CLOCK_MONOTONIC
+ *
+ * This function is intended to provide to the input system a more
+ * accurate time of when an event actually occurred. The driver should
+ * call this function as soon as a timestamp is acquired ensuring
+ * clock conversions in input_set_timestamp are done correctly.
+ *
+ * The system entering suspend state between timestamp acquisition and
+ * calling input_set_timestamp can result in inaccurate conversions.
+ */
+void input_set_timestamp(struct input_dev *dev, ktime_t timestamp)
+{
+	dev->timestamp[INPUT_CLK_MONO] = timestamp;
+	dev->timestamp[INPUT_CLK_REAL] = ktime_mono_to_real(timestamp);
+	dev->timestamp[INPUT_CLK_BOOT] = ktime_mono_to_any(timestamp,
+							   TK_OFFS_BOOT);
+}
+EXPORT_SYMBOL(input_set_timestamp);
+
+/**
+ * input_get_timestamp - get timestamp for input events
+ * @dev: input device to get timestamp from
+ *
+ * A valid timestamp is a timestamp of non-zero value.
+ */
+ktime_t *input_get_timestamp(struct input_dev *dev)
+{
+	const ktime_t invalid_timestamp = ktime_set(0, 0);
+
+	if (!ktime_compare(dev->timestamp[INPUT_CLK_MONO], invalid_timestamp))
+		input_set_timestamp(dev, ktime_get());
+
+	return dev->timestamp;
+}
+EXPORT_SYMBOL(input_get_timestamp);
+
+/**
  * input_set_capability - mark device as capable of a certain event
  * @dev: device that is capable of emitting or accepting event
  * @type: type of the event (EV_KEY, EV_REL, etc...)