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Commit 52ea8996 authored by Peter Hutterer's avatar Peter Hutterer Committed by Benjamin Tissoires
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Input: add `REL_WHEEL_HI_RES` and `REL_HWHEEL_HI_RES` 

This event code represents scroll reports from high-resolution wheels and
is modelled after the approach Windows uses. The value 120 is one detent
(wheel click) of movement. Mice with higher-resolution scrolling can send
fractions of 120 which must be accumulated in userspace. Userspace can either
wait for a full 120 to accumulate or scroll by fractions of one logical scroll
movement as the events come in. 120 was picked as magic number because it has
a high number of integer fractions that can be used by high-resolution wheels.

For more information see
https://docs.microsoft.com/en-us/previous-versions/windows/hardware/design/dn613912(v=vs.85)



These new axes obsolete REL_WHEEL and REL_HWHEEL. The legacy axes are emulated
by the kernel but the most accurate (and most granular) data is available
through the new axes.

Signed-off-by: default avatarPeter Hutterer <peter.hutterer@who-t.net>
Acked-by: default avatarDmitry Torokhov <dmitry.torokhov@gmail.com>
Verified-by: default avatarHarry Cutts <hcutts@chromium.org>
Signed-off-by: default avatarBenjamin Tissoires <benjamin.tissoires@redhat.com>
parent e195ca6c

Documentation/input/event-codes.rst

+20 −1
Original line number Diff line number Diff line
@@ -190,7 +190,26 @@ A few EV_REL codes have special meanings: 
* REL_WHEEL, REL_HWHEEL:



  - These codes are used for vertical and horizontal scroll wheels,

    respectively.

    respectively. The value is the number of detents moved on the wheel, the

    physical size of which varies by device. For high-resolution wheels

    this may be an approximation based on the high-resolution scroll events,

    see REL_WHEEL_HI_RES. These event codes are legacy codes and

    REL_WHEEL_HI_RES and REL_HWHEEL_HI_RES should be preferred where

    available.



* REL_WHEEL_HI_RES, REL_HWHEEL_HI_RES:



  - High-resolution scroll wheel data. The accumulated value 120 represents

    movement by one detent. For devices that do not provide high-resolution

    scrolling, the value is always a multiple of 120. For devices with

    high-resolution scrolling, the value may be a fraction of 120.



    If a vertical scroll wheel supports high-resolution scrolling, this code

    will be emitted in addition to REL_WHEEL or REL_HWHEEL. The REL_WHEEL

    and REL_HWHEEL may be an approximation based on the high-resolution

    scroll events. There is no guarantee that the high-resolution data

    is a multiple of 120 at the time of an emulated REL_WHEEL or REL_HWHEEL

    event.



EV_ABS

------

include/uapi/linux/input-event-codes.h

+2 −0
Original line number Diff line number Diff line
@@ -716,6 +716,8 @@ 
 * the situation described above.

 */

#define REL_RESERVED		0x0a

#define REL_WHEEL_HI_RES	0x0b

#define REL_HWHEEL_HI_RES	0x0c

#define REL_MAX			0x0f

#define REL_CNT			(REL_MAX+1)