> > > , but I'd go for fixing the documentation. And re-reading it, it's not
> > > clear that the doc tells us to have [0,90]. It mentions negative values
> > > and out of ranges too, so we might just as well simply clarify that we
> > > rather have [-90,90], with 0 being "north".
> >
> > ... I'd like the documentation fix to go in together in one go with this
> > patch if possible.
> >
>
> Sounds like a plan.
How about this patch?
Henrik
---
>From b14f92066dfab3f8a255ec7b5a30cb1a864dc62f Mon Sep 17 00:00:00 2001
From: Henrik Rydberg <rydberg@xxxxxxxxxxx>
Date: Wed, 11 Oct 2017 22:41:39 +0200
Subject: [PATCH] Input: docs - clarify the usage of ABS_MT_ORIENTATION
As more drivers start to support touch orientation, clarify how the
value range should be set to match the expected behavior in
userland.
Signed-off-by: Henrik Rydberg <rydberg@xxxxxxxxxxx>
---
Documentation/input/multi-touch-protocol.rst | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/Documentation/input/multi-touch-protocol.rst b/Documentation/input/multi-touch-protocol.rst
index 8035868..a0c5c03 100644
--- a/Documentation/input/multi-touch-protocol.rst
+++ b/Documentation/input/multi-touch-protocol.rst
@@ -269,15 +269,17 @@ ABS_MT_ORIENTATION
The orientation of the touching ellipse. The value should describe a signed
quarter of a revolution clockwise around the touch center. The signed value
range is arbitrary, but zero should be returned for an ellipse aligned with
- the Y axis of the surface, a negative value when the ellipse is turned to
- the left, and a positive value when the ellipse is turned to the
- right. When completely aligned with the X axis, the range max should be
- returned.
+ the Y axis of the surface (north). A negative value should be returned when
+ the ellipse is turned to the left (west), with the smallest value reported
+ when aligned with the negative X axis. The largest value should be returned
+ when aligned with the positive X axis.
+
+ The value range should be specified as [-range_max, range_max].
Touch ellipsis are symmetrical by default. For devices capable of true 360
- degree orientation, the reported orientation must exceed the range max to
+ degree orientation, the reported orientation will exceed range_max, in order to
indicate more than a quarter of a revolution. For an upside-down finger,
- range max * 2 should be returned.
+ +- 2 * range_max should be returned.
Orientation can be omitted if the touch area is circular, or if the
information is not available in the kernel driver. Partial orientation
--
2.14.1
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