linux-kernel - Re: [PATCH 1/9] dt-bindings: HID: i2c-hid: Add "panel" property to i2c-hid backed panels

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Message-ID: <CAD=FV=XJhVaFNcLZ_wA=vnYCVVxjq1NFxdV794C0mmxpqvPL6g@mail.gmail.com>
Date:   Tue, 30 May 2023 09:52:25 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel@...ts.freedesktop.org, linux-input@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>, hsinyi@...gle.com,
        devicetree@...r.kernel.org,
        yangcong5@...qin.corp-partner.google.com,
        linux-kernel@...r.kernel.org, Daniel Vetter <daniel@...ll.ch>,
        linux-arm-msm@...r.kernel.org, cros-qcom-dts-watchers@...omium.org
Subject: Re: [PATCH 1/9] dt-bindings: HID: i2c-hid: Add "panel" property to
 i2c-hid backed panels

Hi,

On Tue, May 30, 2023 at 8:34 AM Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> On 23/05/2023 21:27, Douglas Anderson wrote:
> > As talked about in the patch ("drm/panel: Add a way for other devices
> > to follow panel state"), touchscreens that are connected to panels are
> > generally expected to be power sequenced together with the panel
> > they're attached to. Today, nothing provides information allowing you
> > to find out that a touchscreen is connected to a panel. Let's add a
> > phandle for this.
> >
> > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> > ---
> >
> >  Documentation/devicetree/bindings/input/elan,ekth6915.yaml  | 6 ++++++
> >  Documentation/devicetree/bindings/input/goodix,gt7375p.yaml | 6 ++++++
> >  Documentation/devicetree/bindings/input/hid-over-i2c.yaml   | 6 ++++++
> >  3 files changed, 18 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/input/elan,ekth6915.yaml b/Documentation/devicetree/bindings/input/elan,ekth6915.yaml
> > index 05e6f2df604c..d55b03bd3ec4 100644
> > --- a/Documentation/devicetree/bindings/input/elan,ekth6915.yaml
> > +++ b/Documentation/devicetree/bindings/input/elan,ekth6915.yaml
> > @@ -24,6 +24,12 @@ properties:
> >    interrupts:
> >      maxItems: 1
> >
> > +  panel:
> > +    description: If this is a touchscreen, the panel it's connected to. This
>
> Hm, can there be different setup? Touchscreen without panel? What would
> it be then?

For a touchscreen that's a discrete device (not sharing logic / power
rails with the panel) you'd just leave off the panel node like we've
always done. Assuming folks like this series in general, I'll try to
improve the wording for v2.


> Why only these touchscreens? This looks generic, so maybe in
> touchscreen.yaml?

Ah, that makes sense. I guess we need to add an include of that file
from the elan and goodix bindings. The hid-over-i2c.yaml already has
it, though. I'm not 100% sure the existing "hid-over-i2c" driver in
Linux actually calls the function to parse all those properties, but I
guess that's a Linux problem and not a DT bindings problem. ;-)

-Doug