This patch teaches input_mt_report_pointer_emulation() to synthesize
ABS_TOOL_WIDTH from ABS_MT_WIDTH_MAJOR if the touchpad driver reports
ABS_MT_WIDTH_MAJOR. (As of this commit, the only in-tree drivers that do
are mouse/bcm5974.c and touchscreen/goodix.c.)

Additionally, this patch makes input_mt_report_pointer_emulation() rescale
values from each MT axis range to the respective emulated axis range to
allow touchpad drivers to redefine the emulated axis ranges after calling
input_mt_init_slots(). (The X and Y axes presently are not rescaled.)

Signed-off-by: Matt Whitlock <li...@mattwhitlock.name>
---
 drivers/input/input-mt.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/input/input-mt.c b/drivers/input/input-mt.c
index 54fce56..ccd55d9 100644
--- a/drivers/input/input-mt.c
+++ b/drivers/input/input-mt.c
@@ -23,6 +23,19 @@ static void copy_abs(struct input_dev *dev, unsigned int 
dst, unsigned int src)
        }
 }
 
+static int rescale_abs_value(const struct input_dev *dev, unsigned int dst,
+                       unsigned int src, int value)
+{
+       if (dev->absinfo && test_bit(dst, dev->absbit)
+                       && test_bit(src, dev->absbit)) {
+               struct input_absinfo *di = &dev->absinfo[dst], *si = 
&dev->absinfo[src];
+
+               value = di->minimum + (di->maximum - di->minimum) *
+                               (value - si->minimum) / (si->maximum - 
si->minimum);
+       }
+       return value;
+}
+
 /**
  * input_mt_init_slots() - initialize MT input slots
  * @dev: input device supporting MT events and finger tracking
@@ -65,6 +78,7 @@ int input_mt_init_slots(struct input_dev *dev, unsigned int 
num_slots,
                copy_abs(dev, ABS_X, ABS_MT_POSITION_X);
                copy_abs(dev, ABS_Y, ABS_MT_POSITION_Y);
                copy_abs(dev, ABS_PRESSURE, ABS_MT_PRESSURE);
+               copy_abs(dev, ABS_TOOL_WIDTH, ABS_MT_WIDTH_MAJOR);
        }
        if (flags & INPUT_MT_POINTER) {
                __set_bit(BTN_TOOL_FINGER, dev->keybit);
@@ -230,11 +244,19 @@ void input_mt_report_pointer_emulation(struct input_dev 
*dev, bool use_count)
 
                if (test_bit(ABS_MT_PRESSURE, dev->absbit)) {
                        int p = input_mt_get_value(oldest, ABS_MT_PRESSURE);
+                       p = rescale_abs_value(dev, ABS_PRESSURE, 
ABS_MT_PRESSURE, p);
                        input_event(dev, EV_ABS, ABS_PRESSURE, p);
                }
+               if (test_bit(ABS_MT_WIDTH_MAJOR, dev->absbit)) {
+                       int w = input_mt_get_value(oldest, ABS_MT_WIDTH_MAJOR);
+                       w = rescale_abs_value(dev, ABS_TOOL_WIDTH, 
ABS_MT_WIDTH_MAJOR, w);
+                       input_event(dev, EV_ABS, ABS_TOOL_WIDTH, w);
+               }
        } else {
                if (test_bit(ABS_MT_PRESSURE, dev->absbit))
                        input_event(dev, EV_ABS, ABS_PRESSURE, 0);
+               if (test_bit(ABS_MT_WIDTH_MAJOR, dev->absbit))
+                       input_event(dev, EV_ABS, ABS_TOOL_WIDTH, 0);
        }
 }
 EXPORT_SYMBOL(input_mt_report_pointer_emulation);
-- 
2.4.2

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