From: Angela Czubak <aczubak@google.com>

Add a flag to generate ABS_PRESSURE as sum of ABS_MT_PRESSURE across
all slots.
This flag should be set if one knows a device reports true force and would
like to report total force to the userspace.

Signed-off-by: Angela Czubak <aczubak@google.com>
Co-developed-by: Jonathan Denose <jdenose@google.com>
Signed-off-by: Jonathan Denose <jdenose@google.com>
---
 drivers/input/input-mt.c | 14 ++++++++++----
 include/linux/input/mt.h |  1 +
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/input/input-mt.c b/drivers/input/input-mt.c
index 337006dd9dcf72ef2eeb8580e4dd83babf8100be..09f518897d4a71a4a7625367dc2c652ee6035d98 100644
--- a/drivers/input/input-mt.c
+++ b/drivers/input/input-mt.c
@@ -198,6 +198,7 @@ void input_mt_report_pointer_emulation(struct input_dev *dev, bool use_count)
 	struct input_mt *mt = dev->mt;
 	struct input_mt_slot *oldest;
 	int oldid, count, i;
+	int p, reported_p = 0;
 
 	if (!mt)
 		return;
@@ -216,6 +217,13 @@ void input_mt_report_pointer_emulation(struct input_dev *dev, bool use_count)
 			oldest = ps;
 			oldid = id;
 		}
+		if (test_bit(ABS_MT_PRESSURE, dev->absbit)) {
+			p = input_mt_get_value(ps, ABS_MT_PRESSURE);
+			if (mt->flags & INPUT_MT_TOTAL_FORCE)
+				reported_p += p;
+			else if (oldid == id)
+				reported_p = p;
+		}
 		count++;
 	}
 
@@ -245,10 +253,8 @@ void input_mt_report_pointer_emulation(struct input_dev *dev, bool use_count)
 		input_event(dev, EV_ABS, ABS_X, x);
 		input_event(dev, EV_ABS, ABS_Y, y);
 
-		if (test_bit(ABS_MT_PRESSURE, dev->absbit)) {
-			int p = input_mt_get_value(oldest, ABS_MT_PRESSURE);
-			input_event(dev, EV_ABS, ABS_PRESSURE, p);
-		}
+		if (test_bit(ABS_MT_PRESSURE, dev->absbit))
+			input_event(dev, EV_ABS, ABS_PRESSURE, reported_p);
 	} else {
 		if (test_bit(ABS_MT_PRESSURE, dev->absbit))
 			input_event(dev, EV_ABS, ABS_PRESSURE, 0);
diff --git a/include/linux/input/mt.h b/include/linux/input/mt.h
index 2cf89a538b18bbc7c99c8705c2d22bdc95065238..d30286298a00a356bc9db954ae362f034cdd359b 100644
--- a/include/linux/input/mt.h
+++ b/include/linux/input/mt.h
@@ -17,6 +17,7 @@
 #define INPUT_MT_DROP_UNUSED	0x0004	/* drop contacts not seen in frame */
 #define INPUT_MT_TRACK		0x0008	/* use in-kernel tracking */
 #define INPUT_MT_SEMI_MT	0x0010	/* semi-mt device, finger count handled manually */
+#define INPUT_MT_TOTAL_FORCE	0x0020	/* calculate total force from slots pressure */
 
 /**
  * struct input_mt_slot - represents the state of an input MT slot

-- 
2.51.0.rc1.163.g2494970778-goog