Input: estimate number of events per packet

Calculate a default based on the number of ABS axes, REL axes,
and MT slots for the device during input device registration.

Signed-off-by: Jeff Brown <jeffbrown@android.com>
Reviewed-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

2 files changed, 46 insertions, 0 deletions

diff --git a/drivers/input/input.c b/drivers/input/input.c
index d6e8bd8a851c..ebbceedc92f4 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -1746,6 +1746,42 @@ void input_set_capability(struct input_dev *dev, unsigned int type, unsigned int
 }
 EXPORT_SYMBOL(input_set_capability);
 
+static unsigned int input_estimate_events_per_packet(struct input_dev *dev)
+{
+        int mt_slots;
+        int i;
+        unsigned int events;
+
+        if (dev->mtsize) {
+                mt_slots = dev->mtsize;
+        } else if (test_bit(ABS_MT_TRACKING_ID, dev->absbit)) {
+                mt_slots = dev->absinfo[ABS_MT_TRACKING_ID].maximum -
+                           dev->absinfo[ABS_MT_TRACKING_ID].minimum + 1,
+                clamp(mt_slots, 2, 32);
+        } else if (test_bit(ABS_MT_POSITION_X, dev->absbit)) {
+                mt_slots = 2;
+        } else {
+                mt_slots = 0;
+        }
+
+        events = mt_slots + 1; /* count SYN_MT_REPORT and SYN_REPORT */
+
+        for (i = 0; i < ABS_CNT; i++) {
+                if (test_bit(i, dev->absbit)) {
+                        if (input_is_mt_axis(i))
+                                events += mt_slots;
+                        else
+                                events++;
+                }
+        }
+
+        for (i = 0; i < REL_CNT; i++)
+                if (test_bit(i, dev->relbit))
+                        events++;
+
+        return events;
+}
+
 #define INPUT_CLEANSE_BITMASK(dev, type, bits)                          \
         do {                                                            \
                 if (!test_bit(EV_##type, dev->evbit))                   \
@@ -1793,6 +1829,10 @@ int input_register_device(struct input_dev *dev)
         /* Make sure that bitmasks not mentioned in dev->evbit are clean. */
         input_cleanse_bitmasks(dev);
 
+        if (!dev->hint_events_per_packet)
+                dev->hint_events_per_packet =
+                                input_estimate_events_per_packet(dev);
+
         /*
          * If delay and period are pre-set by the driver, then autorepeating
          * is handled by the driver itself and we don't do it in input.c.
diff --git a/include/linux/input/mt.h b/include/linux/input/mt.h
index b3ac06a4435d..318bb82325a6 100644
--- a/include/linux/input/mt.h
+++ b/include/linux/input/mt.h
@@ -48,6 +48,12 @@ static inline void input_mt_slot(struct input_dev *dev, int slot)
         input_event(dev, EV_ABS, ABS_MT_SLOT, slot);
 }
 
+static inline bool input_is_mt_axis(int axis)
+{
+        return axis == ABS_MT_SLOT ||
+                (axis >= ABS_MT_FIRST && axis <= ABS_MT_LAST);
+}
+
 void input_mt_report_slot_state(struct input_dev *dev,
                                 unsigned int tool_type, bool active);