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Date:   Sat, 05 Nov 2022 23:39:32 +0000
From:   Paul Cercueil <paul@crapouillou.net>
Subject: Re: [RFC PATCH 0/2] Input: adc-joystick: add detachable devices
 support
To:     Siarhei Volkau <lis8215@gmail.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Artur Rojek <contact@artur-rojek.eu>,
        linux-input@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
Message-Id: <W1FWKR.P26T1W42X3ND@crapouillou.net>
In-Reply-To: <20221031190159.1341027-1-lis8215@gmail.com>
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Hi Siarhei,

Le lun. 31 oct. 2022 =E0 22:01:57 +0300, Siarhei Volkau=20
<lis8215@gmail.com> a =E9crit :
> For detachable or lock-able joysticks the ADC lanes might
> be biased to GND or AVDD when the joystick is detached/locked.
>=20
> One such kind of joystick is found in the Ritmix RZX-50 handheld.
> The joystick is non-detachable, although ADC lane biased to power
> supply when the "Hold" switch is activated.

But the RZX-50 has no joystick...
Or is the d-pad actually wired to the ADC instead of GPIOs?

> To avoid reporting old/broken measurements valid-range is introduced.
> When measured value is outside valid-range the driver reports
> safe center position for corresponding axis.

First of all, you already have a "valid range", it is called=20
"abs-range"; no need for a new one.

Then, the driver has no business doing events filtering. Notice that=20
when you activate the "hold" button and your joystick values go way=20
off-range, you still get input events in userspace: that's because the=20
kernel is not responsible for enforcing the deadzone, the userspace is.

In your case, you need to update your userspace applications/libraries=20
so that when the joystick values are way off-range, the assumed=20
position is the center.

Cheers,
-Paul