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authorPeter Hutterer <peter.hutterer@who-t.net>2018-12-05 03:42:21 +0300
committerBenjamin Tissoires <benjamin.tissoires@redhat.com>2018-12-07 18:27:11 +0300
commit52ea899637c746984d657b508da6e3f2686adfca (patch)
tree5e710d864a62c37567fce0ad91a5bce45486b2f5 /Documentation/input
parente195ca6cb6f21633e56322d5aa11ed59cdb22fb2 (diff)
downloadlinux-52ea899637c746984d657b508da6e3f2686adfca.tar.xz
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.rst21
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
------