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Subject[PATCH 4/4] HID: input: work around Win8 stylus-on-touchscreen reporting
With this, these devices now behave as tablets as expected by userspace

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
---
drivers/hid/hid-input.c | 41 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 41 insertions(+)

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index a5ba92978473..b8813fc3e9d2 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -1273,6 +1273,41 @@ static void hidinput_handle_scroll(struct hid_usage *usage,
input_event(input, EV_REL, usage->code, hi_res);
}

+/*
+ * Win8 tablet stylus devices send, in order:
+ * HID_DG_TIPSWITCH (BTN_TOUCH)
+ * HID_DG_INVERT (BTN_TOOL_RUBBER)
+ * HID_DG_ERASER (BTN_TOUCH)
+ * HID_DG_INRANGE (BTN_TOOL_PEN)
+ *
+ * For each of these states:
+ * hover : INRANGE
+ * touching : TIPSWITCH
+ * hover+2 : INVERT INRANGE
+ * touching+2: ERASER INRANGE
+ *
+ * Which means we'd send BTN_TOUCH=0 + BTN_TOOL_PEN=1 on proximity,
+ * then BTN_TOUCH=1 and BTN_TOOL_PEN=0 in consecutive groups when touched,
+ * indicating the stylus leaving the screen as soon as the two meet.
+ */
+static void hidinput_fixup_win8_inrange(struct hid_device *hid, struct hid_field *field, __s32 *value)
+{
+ unsigned f, u;
+ struct hid_field *rfield;
+
+ if (!*value) {
+ for (f = 0; f < field->report->maxfield; ++f) {
+ rfield = field->report->field[f];
+ for (u = 0; u < rfield->maxusage; ++u) {
+ if (rfield->usage[u].hid == HID_DG_TIPSWITCH) {
+ *value = rfield->value[u];
+ return;
+ }
+ }
+ }
+ }
+}
+
void hidinput_hid_event(struct hid_device *hid, struct hid_field *field, struct hid_usage *usage, __s32 value)
{
struct input_dev *input;
@@ -1306,7 +1341,13 @@ void hidinput_hid_event(struct hid_device *hid, struct hid_field *field, struct
return;
}

+ if (usage->hid == HID_DG_ERASER && value)
+ *quirks |= HID_QUIRK_INVERT;
+
if (usage->hid == HID_DG_INRANGE) {
+ if (hid->group == HID_GROUP_MULTITOUCH_WIN_8)
+ hidinput_fixup_win8_inrange(hid, field, &value);
+
if (value) {
input_event(input, usage->type, (*quirks & HID_QUIRK_INVERT) ? BTN_TOOL_RUBBER : usage->code, 1);
return;
--
2.20.1[unhandled content-type:application/pgp-signature]
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