On Wed, 23 Sep 2020, Gerecke, Jason wrote:
From: Jason Gerecke jason.gerecke@wacom.com
It has recently been reported that the "heartbeat" report from devices like the 2nd-gen Intuos Pro (PTH-460, PTH-660, PTH-860) or the 2nd-gen Bluetooth-enabled Intuos tablets (CTL-4100WL, CTL-6100WL) can cause the driver to send a spurious BTN_TOUCH=0 once per second in the middle of drawing. This can result in broken lines while drawing on Chrome OS.
The source of the issue has been traced back to a change which modified the driver to only call `wacom_wac_pad_report()` once per report instead of once per collection. As part of this change, pad-handling code was removed from `wacom_wac_collection()` under the assumption that the `WACOM_PEN_FIELD` and `WACOM_TOUCH_FIELD` checks would not be satisfied when a pad or battery collection was being processed.
To be clear, the macros `WACOM_PAD_FIELD` and `WACOM_PEN_FIELD` do not currently check exclusive conditions. In fact, most "pad" fields will also appear to be "pen" fields simply due to their presence inside of a Digitizer application collection. Because of this, the removal of the check from `wacom_wac_collection()` just causes pad / battery collections to instead trigger a call to `wacom_wac_pen_report()` instead. The pen report function in turn resets the tip switch state just prior to exiting, resulting in the observed BTN_TOUCH=0 symptom.
To correct this, we restore a version of the `WACOM_PAD_FIELD` check in `wacom_wac_collection()` and return early. This effectively prevents pad / battery collections from being reported until the very end of the report as originally intended.
Fixes: d4b8efeb46d9 ("HID: wacom: generic: Correct pad syncing") Cc: stable@vger.kernel.org # v4.17+ Signed-off-by: Jason Gerecke jason.gerecke@wacom.com Reviewed-by: Ping Cheng ping.cheng@wacom.com Tested-by: Ping Cheng ping.cheng@wacom.com
Applied.