[PATCH 1/2] HID: input: map HID_GD_Z to ABS_DISTANCE for stylus/pen

[Ping Cheng <pinglinux@gmail.com>]

HID_GD_Z is mapped to ABS_Z for stylus and pen in hid-input.c. But HID_GD_Z
should be used to report ABS_DISTANCE for stylus and pen as described at:
Documentation/input/event-codes.rst#n226

* ABS_DISTANCE:

  - Used to describe the distance of a tool from an interaction surface. This
    event should only be emitted while the tool is hovering, meaning in close
    proximity of the device and while the value of the BTN_TOUCH code is 0. If
    the input device may be used freely in three dimensions, consider ABS_Z
    instead.
  - BTN_TOOL_<name> should be set to 1 when the tool comes into detectable
    proximity and set to 0 when the tool leaves detectable proximity.
    BTN_TOOL_<name> signals the type of tool that is currently detected by the
    hardware and is otherwise independent of ABS_DISTANCE and/or BTN_TOUCH.

This patch makes the correct mapping. The ABS_DISTANCE is currently not mapped
by any HID usage in hid-generic driver.

Signed-off-by: Ping Cheng <ping.cheng@wacom.com>
---
 drivers/hid/hid-input.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index ff1784b5c2a4..240bc8a5f3bc 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -858,8 +858,18 @@ static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_fiel
 			goto ignore;
 
 		switch (usage->hid) {
+		case HID_GD_Z:
+			/* HID_GD_Z is mapped to ABS_DISTANCE for stylus/pen */
+			if ((field->application & 0xff) == 0x02) {
+				if (field->flags & HID_MAIN_ITEM_RELATIVE)
+					map_rel(usage->hid & 0xf);
+				else
+					map_abs_clear(ABS_DISTANCE);
+				break;
+			}
+			/* fall through for other devices/tools */
 		/* These usage IDs map directly to the usage codes. */
-		case HID_GD_X: case HID_GD_Y: case HID_GD_Z:
+		case HID_GD_X: case HID_GD_Y:
 		case HID_GD_RX: case HID_GD_RY: case HID_GD_RZ:
 			if (field->flags & HID_MAIN_ITEM_RELATIVE)
 				map_rel(usage->hid & 0xf);
-- 
2.50.0