On Thu, Jan 26, 2017 at 9:06 AM, Jason Gerecke <killertofu@xxxxxxxxx> wrote:
> Commit 025bcc1 performed cleanup work on the 'wacom_pl_irq' function, making
> it follow the standards used in the rest of the codebase. The change
> unintiontionally allowed the function to send input events from reports
> that are not marked as being in prox. This can cause problems as the
> report values for X, Y, etc. are not guaranteed to be correct. In
> particular, occasionally the tablet will send a report with these values
> set to zero. If such a report is received it can caus an unexpected jump
> in the XY position.
>
> This patch surrounds more of the processing code with a proximity check,
> preventing these zeroed reports from overwriting the current state. To
> be safe, only the tool type and ABS_MISC events should be reported when
> the pen is marked as being out of prox.
>
> Fixes: 025bcc1540 ("HID: wacom: Simplify 'wacom_pl_irq'")
> Signed-off-by: Jason Gerecke <jason.gerecke@xxxxxxxxx>
Reviewed-by: Ping Cheng <pingc@xxxxxxxxx>
Cheers,
Ping
P.S., this patch has been tested by users at linuxwacom.sf.net
> ---
> drivers/hid/wacom_wac.c | 28 +++++++++++++++-------------
> 1 file changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
> index 0884dc9554fd..672145b0d8f5 100644
> --- a/drivers/hid/wacom_wac.c
> +++ b/drivers/hid/wacom_wac.c
> @@ -166,19 +166,21 @@ static int wacom_pl_irq(struct wacom_wac *wacom)
> wacom->id[0] = STYLUS_DEVICE_ID;
> }
>
> - pressure = (signed char)((data[7] << 1) | ((data[4] >> 2) & 1));
> - if (features->pressure_max > 255)
> - pressure = (pressure << 1) | ((data[4] >> 6) & 1);
> - pressure += (features->pressure_max + 1) / 2;
> -
> - input_report_abs(input, ABS_X, data[3] | (data[2] << 7) | ((data[1] & 0x03) << 14));
> - input_report_abs(input, ABS_Y, data[6] | (data[5] << 7) | ((data[4] & 0x03) << 14));
> - input_report_abs(input, ABS_PRESSURE, pressure);
> -
> - input_report_key(input, BTN_TOUCH, data[4] & 0x08);
> - input_report_key(input, BTN_STYLUS, data[4] & 0x10);
> - /* Only allow the stylus2 button to be reported for the pen tool. */
> - input_report_key(input, BTN_STYLUS2, (wacom->tool[0] == BTN_TOOL_PEN) && (data[4] & 0x20));
> + if (prox) {
> + pressure = (signed char)((data[7] << 1) | ((data[4] >> 2) & 1));
> + if (features->pressure_max > 255)
> + pressure = (pressure << 1) | ((data[4] >> 6) & 1);
> + pressure += (features->pressure_max + 1) / 2;
> +
> + input_report_abs(input, ABS_X, data[3] | (data[2] << 7) | ((data[1] & 0x03) << 14));
> + input_report_abs(input, ABS_Y, data[6] | (data[5] << 7) | ((data[4] & 0x03) << 14));
> + input_report_abs(input, ABS_PRESSURE, pressure);
> +
> + input_report_key(input, BTN_TOUCH, data[4] & 0x08);
> + input_report_key(input, BTN_STYLUS, data[4] & 0x10);
> + /* Only allow the stylus2 button to be reported for the pen tool. */
> + input_report_key(input, BTN_STYLUS2, (wacom->tool[0] == BTN_TOOL_PEN) && (data[4] & 0x20));
> + }
>
> if (!prox)
> wacom->id[0] = 0;
> --
> 2.11.0
>
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