[PATCH] bcm5974: report ABS_MT_PRESSURE

[Ryan Hendrickson <ryan.hendrickson@alum.mit.edu>]

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Report ABS_MT_PRESSURE in the bcm5974 driver with the same data used for
ABS_PRESSURE.

Some touchpad improvements in recent versions of libinput, such as
pressure-based palm detection, will only work if ABS_MT_PRESSURE is
reported.

Signed-off-by: Ryan Hendrickson <ryan.hendrickson@alum.mit.edu>

---

Please treat all of this with an extra grain of salt; this is my first real
foray into both evdev/libinput internals and kernel development. That said,
I have been running this patch on my daily-use MacBookPro5,1 for several
months, so I have reason to believe it's stable. It might not be the
‘right’ way to do this though; I mostly just copied the corresponding code
for ABS_PRESSURE, which from this[1] blog post I've inferred should have
the same values and range.

[1]: http://who-t.blogspot.com/2016/09/understanding-evdev.html

Patch was originally submitted as bug 197909[2], which can be closed if
this is accepted.

[2]: https://bugzilla.kernel.org/show_bug.cgi?id=197909

--- linux-4.13/drivers/input/mouse/bcm5974.c.orig	2017-12-01 11:36:35.258890243 -0500
+++ linux-4.13/drivers/input/mouse/bcm5974.c	2017-12-01 11:48:55.187342210 -0500
@@ -548,6 +548,8 @@ static void setup_events_to_report(struc
  	set_abs(input_dev, ABS_MT_POSITION_X, &cfg->x);
  	set_abs(input_dev, ABS_MT_POSITION_Y, &cfg->y);

+	set_abs(input_dev, ABS_MT_PRESSURE, &cfg->p);
+
  	__set_bit(EV_KEY, input_dev->evbit);
  	__set_bit(BTN_LEFT, input_dev->keybit);

@@ -575,10 +577,14 @@ static int report_bt_state(struct bcm597
  	return 0;
  }

-static void report_finger_data(struct input_dev *input, int slot,
+static void report_finger_data(struct input_dev *input,
+			       const struct bcm5974_config *cfg,
+			       int slot,
  			       const struct input_mt_pos *pos,
  			       const struct tp_finger *f)
  {
+	int abs_p;
+
  	input_mt_slot(input, slot);
  	input_mt_report_slot_state(input, MT_TOOL_FINGER, true);

@@ -594,6 +600,9 @@ static void report_finger_data(struct in
  			 MAX_FINGER_ORIENTATION - raw2int(f->orientation));
  	input_report_abs(input, ABS_MT_POSITION_X, pos->x);
  	input_report_abs(input, ABS_MT_POSITION_Y, pos->y);
+
+	abs_p = clamp_val(256 * raw2int(f->touch_major) / cfg->p.max, 0, 255);
+	input_report_abs(input, ABS_MT_PRESSURE, abs_p);
  }

  static void report_synaptics_data(struct input_dev *input,
@@ -640,7 +649,7 @@ static int report_tp_state(struct bcm597
  	input_mt_assign_slots(input, dev->slots, dev->pos, n, 0);

  	for (i = 0; i < n; i++)
-		report_finger_data(input, dev->slots[i],
+		report_finger_data(input, c, dev->slots[i],
  				   &dev->pos[i], dev->index[i]);

  	input_mt_sync_frame(input);