On Fri, Dec 15, 2023 at 12:19:51PM +0100, Artur Rojek wrote:
> On 2023-12-15 03:40, Chris Morgan wrote:
> > From: Chris Morgan <macromorgan@xxxxxxxxxxx>
> >
> > uinput refuses to work with abs devices where the min value is greater
> > than the max value. uinput_validate_absinfo() returns -EINVAL if this
> > is the case and prevents using uinput on such a device. Since uinput
> > has worked this way since at least kernel 2.6 (or prior) I presume that
> > this is the correct way of doing things, and that this documentation
> > needs to be clarified that min must always be less than max.
> >
> > uinput is used in my use case to bind together adc-joystick devices
> > with gpio-keys devices to create a single unified gamepad for
> > userspace.
> >
> > Note that there are several boards that will need to be corrected,
> > all but a few of them I maintain. Submitting as an RFC for now to get
> > comments from the input team and the original author in case there is
> > something I am missing.
> >
> > Fixes: 7956b0d4694f ("dt-bindings: input: Add docs for ADC driven
> > joystick")
> >
> > Signed-off-by: Chris Morgan <macromorgan@xxxxxxxxxxx>
> > ---
> > Documentation/devicetree/bindings/input/adc-joystick.yaml | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/input/adc-joystick.yaml
> > b/Documentation/devicetree/bindings/input/adc-joystick.yaml
> > index 6c244d66f8ce..8f5cdd5ef190 100644
> > --- a/Documentation/devicetree/bindings/input/adc-joystick.yaml
> > +++ b/Documentation/devicetree/bindings/input/adc-joystick.yaml
> > @@ -73,8 +73,9 @@ patternProperties:
> > description: >
> > Minimum and maximum values produced by the axis.
> > For an ABS_X axis this will be the left-most and right-most
> > - inclination of the joystick. If min > max, it is left to
> > userspace to
> > - treat the axis as inverted.
> > + inclination of the joystick. The axis must always be
> > expressed as
> > + min < max, if the axis is inverted it is left to userspace to
> > handle
> > + the inversion.
>
> Hi Chris,
>
> Device Tree is supposed to depict the actual state of the hardware.
> I worded the adc-joytick's adc-range property specifically, so that it
> covers a case of GCW Zero hardware [1], which has a joystick, where the
> ABS_X axis reports increasing values for the left-wards inclination of
> the joystick, and decreasing values for the right-wards inclination. You
> are saying that there are even more boards that need to be corrected -
> those are all situations, where DT depicts the actual behavior of the
> hardware.
> What you are trying to do is change hardware description, because of how
> a driver in an OS works. You should instead fix behavior of said driver,
> even if nobody stumbled upon that issue since 2.6 :) We fixed libSDL [2]
> for the same reason.
>
> Cheers,
> Artur
>
> PS. cc'd Paul to the conversation.
>
> [1] https://github.com/OpenDingux/linux/blob/jz-6.1/arch/mips/boot/dts/ingenic/gcw0.dts#L273C12-L273C12
> [2] https://github.com/libsdl-org/SDL-1.2/commit/46806790ad043
Thank you. Okay, I'll update uinput instead to drop checks for
min > max, since that's valid/allowed.
Chris
>
> > This property is interpreted as two signed 32 bit values.
> >
> > abs-fuzz:
>
