Commit 5e3e8f1b authored by Benjamin Tissoires's avatar Benjamin Tissoires Committed by Jiri Kosina
Browse files

HID: bpf: add heuristics to the Huion Inspiroy 2S eraser button 



When pressing the phsyical eraser button (remapped by us to the
Secondary Barrel Switch) while the tip is down, the device
gives us several false reports with a Tip Switch 0:

         press|           |release
SBS: [0 0 ... 1 1 1 ... 1 0 0 0 0 0 0 ...]
 TS: [1 1 ... 1 0 1 ... 1 1 0 0 0 1 1 ...]

In both press/release the number of Tip Switch 0 reports can be up to 4
and *sometimes* the Tip Switch is released in the same report
as the button press/release event.

Paper over this by forcing the tip down for a few reports if it was down
before the button toggled.

Signed-off-by: default avatarPeter Hutterer <peter.hutterer@who-t.net>
Link: https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/merge_requests/195


Signed-off-by: default avatarBenjamin Tissoires <bentiss@kernel.org>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.com>
parent 88b5468f

drivers/hid/bpf/progs/Huion__Inspiroy-2-S.bpf.c

+27 −2
Original line number Diff line number Diff line
@@ -163,6 +163,9 @@ char EXPECTED_FIRMWARE_ID[] = "HUION_T21j_"; 




__u8 last_button_state;

__u8 last_tip_state;

__u8 last_sec_barrel_state;

__u8 force_tip_down_count;



static const __u8 fixed_rdesc_pad[] = {

	UsagePage_GenericDesktop
@@ -522,9 +525,31 @@ int BPF_PROG(inspiroy_2_fix_events, struct hid_bpf_ctx *hctx) 
			pad_report->wheel = wheel;



			return sizeof(struct pad_report);

		} else if (data[1] & 0x80) { /* Pen reports with InRange 1 */

			__u8 tip_state = data[1] & 0x1;

			__u8 sec_barrel_state = data[1] & 0x4;



			if (force_tip_down_count > 0) {

				data[1] |= 0x1;

				--force_tip_down_count;

				if (tip_state)

					force_tip_down_count = 0;

			}



		/* Pen reports need nothing done */

			/* Tip was down and we just pressed or released the

			 * secondary barrel switch (the physical eraser

			 * button). The device will send up to 4

			 * reports with Tip Switch 0 and sometimes

			 * this report has Tip Switch 0.

			 */

			if (last_tip_state &&

			    last_sec_barrel_state != sec_barrel_state) {

				force_tip_down_count = 4;

				data[1] |= 0x1;

			}

			last_tip_state = tip_state;

			last_sec_barrel_state = sec_barrel_state;

		}

	}



	return 0;