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author | Peter Hutterer <peter.hutterer@who-t.net> | 2018-12-05 03:42:21 +0300 |
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committer | Benjamin Tissoires <benjamin.tissoires@redhat.com> | 2018-12-07 18:27:11 +0300 |
commit | 52ea899637c746984d657b508da6e3f2686adfca (patch) | |
tree | 5e710d864a62c37567fce0ad91a5bce45486b2f5 /Documentation/input | |
parent | e195ca6cb6f21633e56322d5aa11ed59cdb22fb2 (diff) |
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: Peter Hutterer <peter.hutterer@who-t.net>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Verified-by: Harry Cutts <hcutts@chromium.org>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Diffstat (limited to 'Documentation/input')
-rw-r--r-- | Documentation/input/event-codes.rst | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/Documentation/input/event-codes.rst b/Documentation/input/event-codes.rst index a8c0873beb95..b24b5343f5eb 100644 --- a/Documentation/input/event-codes.rst +++ b/Documentation/input/event-codes.rst @@ -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 ------ |