HID: wacom: Don’t report anything prior to the tool entering range [Linux 4.14.129]

HID: wacom: Don’t report anything prior to the tool entering range [Linux 4.14.129]

This Linux kernel change "HID: wacom: Don’t report anything prior to the tool entering range" is included in the Linux 4.14.129 release. This change is authored by Jason Gerecke <jason.gerecke [at] wacom.com> on Wed Apr 24 15:12:58 2019 -0700. The commit for this change in Linux stable tree is 6fff9ed (patch) which is from upstream commit e92a7be. The same Linux upstream change may have been applied to various maintained Linux releases and you can find all Linux releases containing changes from upstream e92a7be.

HID: wacom: Don't report anything prior to the tool entering range

commit e92a7be7fe5b2510fa60965eaf25f9e3dc08b8cc upstream.

If the tool spends some time in prox before entering range, a series of
events (e.g. ABS_DISTANCE, MSC_SERIAL) can be sent before we or userspace
have any clue about the pen whose data is being reported. We need to hold
off on reporting anything until the pen has entered range. Since we still
want to report events that occur "in prox" after the pen has *left* range
we use 'wacom-tool[0]' as the indicator that the pen did at one point
enter range and provide us/userspace with tool type and serial number
information.

Fixes: a48324de6d4d ("HID: wacom: Bluetooth IRQ for Intuos Pro should handle prox/range")
Cc: <[email protected]> # 4.11+
Signed-off-by: Jason Gerecke <[email protected]>
Reviewed-by: Aaron Armstrong Skomra <[email protected]>
Signed-off-by: Benjamin Tissoires <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

There are 24 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/hid/wacom_wac.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
index 5336336..2748672 100644
--- a/drivers/hid/wacom_wac.c
+++ b/drivers/hid/wacom_wac.c
@@ -1271,17 +1271,19 @@ static void wacom_intuos_pro2_bt_pen(struct wacom_wac *wacom)
            input_report_abs(pen_input, ABS_Z, rotation);
            input_report_abs(pen_input, ABS_WHEEL, get_unaligned_le16(&frame[11]));
        }
-       input_report_abs(pen_input, ABS_PRESSURE, get_unaligned_le16(&frame[5]));
-       input_report_abs(pen_input, ABS_DISTANCE, range ? frame[13] : wacom->features.distance_max);
-
-       input_report_key(pen_input, BTN_TOUCH, frame[0] & 0x01);
-       input_report_key(pen_input, BTN_STYLUS, frame[0] & 0x02);
-       input_report_key(pen_input, BTN_STYLUS2, frame[0] & 0x04);
-
-       input_report_key(pen_input, wacom->tool[0], prox);
-       input_event(pen_input, EV_MSC, MSC_SERIAL, wacom->serial[0]);
-       input_report_abs(pen_input, ABS_MISC,
-                wacom_intuos_id_mangle(wacom->id[0])); /* report tool id */
+       if (wacom->tool[0]) {
+           input_report_abs(pen_input, ABS_PRESSURE, get_unaligned_le16(&frame[5]));
+           input_report_abs(pen_input, ABS_DISTANCE, range ? frame[13] : wacom->features.distance_max);
+
+           input_report_key(pen_input, BTN_TOUCH, frame[0] & 0x01);
+           input_report_key(pen_input, BTN_STYLUS, frame[0] & 0x02);
+           input_report_key(pen_input, BTN_STYLUS2, frame[0] & 0x04);
+
+           input_report_key(pen_input, wacom->tool[0], prox);
+           input_event(pen_input, EV_MSC, MSC_SERIAL, wacom->serial[0]);
+           input_report_abs(pen_input, ABS_MISC,
+                    wacom_intuos_id_mangle(wacom->id[0])); /* report tool id */
+       }

        wacom->shared->stylus_in_proximity = prox;

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