HID_DG_PEN devices should have a suffix of "Stylus", as pointed out by
commit c0ee1d571626 ("HID: hid-input: Add suffix also for HID_DG_PEN").
However, on multitouch devices, these suffixes may be overridden. Before
that commit, HID_DG_PEN devices would get the "Stylus" suffix, but after
that, multitouch would override them to have an "UNKNOWN" suffix. Just add
HID_DG_PEN to the list of non-overriden suffixes in multitouch.

Before this fix:

[    0.470981] input: ELAN9008:00 04F3:2E14 UNKNOWN as /devices/pci0000:00/0000:00:15.1/i2c_designware.1/i2c-16/i2c-ELAN9008:00/0018:04F3:2E14.0001/input/input8
ELAN9008:00 04F3:2E14 UNKNOWN

After this fix:

[    0.474332] input: ELAN9008:00 04F3:2E14 Stylus as /devices/pci0000:00/0000:00:15.1/i2c_designware.1/i2c-16/i2c-ELAN9008:00/0018:04F3:2E14.0001/input/input8

ELAN9008:00 04F3:2E14 Stylus

Fixes: c0ee1d571626 ("HID: hid-input: Add suffix also for HID_DG_PEN")
Signed-off-by: Thadeu Lima de Souza Cascardo <redacted>
---
 drivers/hid/hid-multitouch.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 2879e65cf303b1456311ac06115adda5a78a2600..513b8673ad8dd7ad135652f787812072d45e6c1a 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c

@@ -1742,6 +1742,7 @@ static int mt_input_configured(struct hid_device *hdev, struct hid_input *hi)
 	case HID_CP_CONSUMER_CONTROL:
 	case HID_GD_WIRELESS_RADIO_CTLS:
 	case HID_GD_SYSTEM_MULTIAXIS:
+	case HID_DG_PEN:
 		/* already handled by hid core */
 		break;
 	case HID_DG_TOUCHSCREEN:

---
base-commit: c746c3b5169831d7fb032a1051d8b45592ae8d78
change-id: 20251008-hid_multitouch_stylus-9d2d20d86108

Best regards,
-- 
Thadeu Lima de Souza Cascardo [off-list ref]