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

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

[Ping Cheng]

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

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

[Jiri Kosina]

Both applied to hid.git#for-6.18/core, thanks.

-- 
Jiri Kosina
SUSE Labs

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

[Cheng, Ping]

Hi Jiri,

Please revert this patchset since I need help from Benjamin to make the selftest real. Patch 2 does not do its job...

Thank you for your effort. And sorry for the trouble.
Ping

________________________________________
From: Jiri Kosina <jikos@kernel.org>
Sent: Tuesday, August 12, 2025 5:35 AM
To: Ping Cheng <pinglinux@gmail.com>
Cc: linux-input@vger.kernel.org <linux-input@vger.kernel.org>; bentiss@kernel.org <bentiss@kernel.org>; Dmitry.Torokhov@gmail.com <Dmitry.Torokhov@gmail.com>; stable@kernel.org <stable@kernel.org>; Cheng, Ping <Ping.Cheng@wacom.com>
Subject: Re: [PATCH 1/2] HID: input: map HID_GD_Z to ABS_DISTANCE for stylus/pen

Both applied to hid.git#for-6.18/core, thanks.

--
Jiri Kosina
SUSE Labs

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

[Benjamin Tissoires]

On Aug 12 2025, Cheng, Ping wrote:
> Hi Jiri,
> 
> Please revert this patchset since I need help from Benjamin to make the selftest real. Patch 2 does not do its job...

Furthermore:
  CC      drivers/hid/hid-input.o
drivers/hid/hid-input.c: In function 'hidinput_configure_usage':
drivers/hid/hid-input.c:863:28: error: this statement may fall through [-Werror=implicit-fallthrough=]
  863 |                         if ((field->application & 0xff) == 0x02) {
      |                            ^
drivers/hid/hid-input.c:872:17: note: here
  872 |                 case HID_GD_X: case HID_GD_Y:
      |                 ^~~~

So this breaks compilation entirely :(

[Sorry I'm just back from vacations, and hadn't had the time to look at
the pile of emails]

Cheers,
Benjamin

> 
> Thank you for your effort. And sorry for the trouble.
> Ping
> 
> ________________________________________
> From: Jiri Kosina <jikos@kernel.org>
> Sent: Tuesday, August 12, 2025 5:35 AM
> To: Ping Cheng <pinglinux@gmail.com>
> Cc: linux-input@vger.kernel.org <linux-input@vger.kernel.org>; bentiss@kernel.org <bentiss@kernel.org>; Dmitry.Torokhov@gmail.com <Dmitry.Torokhov@gmail.com>; stable@kernel.org <stable@kernel.org>; Cheng, Ping <Ping.Cheng@wacom.com>
> Subject: Re: [PATCH 1/2] HID: input: map HID_GD_Z to ABS_DISTANCE for stylus/pen
> 
> Both applied to hid.git#for-6.18/core, thanks.
> 
> --
> Jiri Kosina
> SUSE Labs

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

[Jiri Kosina]

On Tue, 12 Aug 2025, Benjamin Tissoires wrote:

> On Aug 12 2025, Cheng, Ping wrote:
> > Hi Jiri,
> > 
> > Please revert this patchset since I need help from Benjamin to make the selftest real. Patch 2 does not do its job...
> 
> Furthermore:
>   CC      drivers/hid/hid-input.o
> drivers/hid/hid-input.c: In function 'hidinput_configure_usage':
> drivers/hid/hid-input.c:863:28: error: this statement may fall through [-Werror=implicit-fallthrough=]
>   863 |                         if ((field->application & 0xff) == 0x02) {
>       |                            ^
> drivers/hid/hid-input.c:872:17: note: here
>   872 |                 case HID_GD_X: case HID_GD_Y:
>       |                 ^~~~
> 
> So this breaks compilation entirely :(

Hm, I really wonder how this escaped me, as I always run a compile+boot 
battery before pushing out.
Sorry for the hassle, I'll investigate more where the glitch was on the 
side of my automation.

Now dropped.

-- 
Jiri Kosina
SUSE Labs