Input: of_touchscreen - add support for touchscreen-min-x|y

Some touchscreens, depending on the firmware and/or the digitizer, report
coordinates which never reach 0 along one or both of their axis.

This has been seen for example on the Silead touchscreens on a Onda V891w
and a Point of View mobii TAB-P800w(v2.0).

This commit adds support for touchscreen-min-x and touchscreen-min-y
device-properties which can be set to communicate the actual start
coordinates (rather then 0,0) to userspace.

This commit also drop the "(in pixels)" comment from the documentation
of the touchscreen-size-x and touchscreen-size-y properties. The comment
suggested that there is a relation between the range of reported
coordinates and the display resolution, which is only true for some
devices. The "(in pixels)" comment is replaced with "(maximum x coordinate
reported + 1)" to mirror the language describing the new touchscreen-min-x
and -min-y properties.

When set this fixes e.g. not being able to click things in the GNOME3
top-bar on the 2 example tablets.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt

 General Touchscreen Properties:
 
 Optional properties for Touchscreens:
+ - touchscreen-min-x		: minimum x coordinate reported (0 if not set)
+ - touchscreen-min-y		: minimum y coordinate reported (0 if not set)
  - touchscreen-size-x		: horizontal resolution of touchscreen
-				  (in pixels)
+				  (maximum x coordinate reported + 1)
  - touchscreen-size-y		: vertical resolution of touchscreen
-				  (in pixels)
+				  (maximum y coordinate reported + 1)
  - touchscreen-max-pressure	: maximum reported pressure (arbitrary range
 				  dependent on the controller)
  - touchscreen-fuzz-x		: horizontal noise value of the absolute input

drivers/input/touchscreen/of_touchscreen.c

@@ -35,7 +35,7 @@ static bool touchscreen_get_prop_u32(struct device *dev,
 
 static void touchscreen_set_params(struct input_dev *dev,
 				   unsigned long axis,
-				   int max, int fuzz)
+				   int min, int max, int fuzz)
 {
 	struct input_absinfo *absinfo;
 
@@ -47,6 +47,7 @@ static void touchscreen_set_params(struct input_dev *dev,
 	}
 
 	absinfo = &dev->absinfo[axis];
+	absinfo->minimum = min;
 	absinfo->maximum = max;
 	absinfo->fuzz = fuzz;
 }
@@ -68,8 +69,9 @@ void touchscreen_parse_properties(struct input_dev *input, bool multitouch,
 				  struct touchscreen_properties *prop)
 {
 	struct device *dev = input->dev.parent;
+	struct input_absinfo *absinfo;
 	unsigned int axis;
-	unsigned int maximum, fuzz;
+	unsigned int minimum, maximum, fuzz;
 	bool data_present;
 
 	input_alloc_absinfo(input);
@@ -77,7 +79,10 @@ void touchscreen_parse_properties(struct input_dev *input, bool multitouch,
 		return;
 
 	axis = multitouch ? ABS_MT_POSITION_X : ABS_X;
-	data_present = touchscreen_get_prop_u32(dev, "touchscreen-size-x",
+	data_present = touchscreen_get_prop_u32(dev, "touchscreen-min-x",
+						input_abs_get_min(input, axis),
+						&minimum) |
+		       touchscreen_get_prop_u32(dev, "touchscreen-size-x",
 						input_abs_get_max(input,
 								  axis) + 1,
 						&maximum) |
@@ -85,10 +90,13 @@ void touchscreen_parse_properties(struct input_dev *input, bool multitouch,
 						input_abs_get_fuzz(input, axis),
 						&fuzz);
 	if (data_present)
-		touchscreen_set_params(input, axis, maximum - 1, fuzz);
+		touchscreen_set_params(input, axis, minimum, maximum - 1, fuzz);
 
 	axis = multitouch ? ABS_MT_POSITION_Y : ABS_Y;
-	data_present = touchscreen_get_prop_u32(dev, "touchscreen-size-y",
+	data_present = touchscreen_get_prop_u32(dev, "touchscreen-min-y",
+						input_abs_get_min(input, axis),
+						&minimum) |
+		       touchscreen_get_prop_u32(dev, "touchscreen-size-y",
 						input_abs_get_max(input,
 								  axis) + 1,
 						&maximum) |
@@ -96,7 +104,7 @@ void touchscreen_parse_properties(struct input_dev *input, bool multitouch,
 						input_abs_get_fuzz(input, axis),
 						&fuzz);
 	if (data_present)
-		touchscreen_set_params(input, axis, maximum - 1, fuzz);
+		touchscreen_set_params(input, axis, minimum, maximum - 1, fuzz);
 
 	axis = multitouch ? ABS_MT_PRESSURE : ABS_PRESSURE;
 	data_present = touchscreen_get_prop_u32(dev,
@@ -108,7 +116,7 @@ void touchscreen_parse_properties(struct input_dev *input, bool multitouch,
 						input_abs_get_fuzz(input, axis),
 						&fuzz);
 	if (data_present)
-		touchscreen_set_params(input, axis, maximum, fuzz);
+		touchscreen_set_params(input, axis, 0, maximum, fuzz);
 
 	if (!prop)
 		return;
@@ -117,13 +125,25 @@ void touchscreen_parse_properties(struct input_dev *input, bool multitouch,
 
 	prop->max_x = input_abs_get_max(input, axis);
 	prop->max_y = input_abs_get_max(input, axis + 1);
+
 	prop->invert_x =
 		device_property_read_bool(dev, "touchscreen-inverted-x");
+	if (prop->invert_x) {
+		absinfo = &input->absinfo[axis];
+		absinfo->maximum -= absinfo->minimum;
+		absinfo->minimum = 0;
+	}
+
 	prop->invert_y =
 		device_property_read_bool(dev, "touchscreen-inverted-y");
+	if (prop->invert_y) {
+		absinfo = &input->absinfo[axis + 1];
+		absinfo->maximum -= absinfo->minimum;
+		absinfo->minimum = 0;
+	}
+
 	prop->swap_x_y =
 		device_property_read_bool(dev, "touchscreen-swapped-x-y");
-
 	if (prop->swap_x_y)
 		swap(input->absinfo[axis], input->absinfo[axis + 1]);
 }