linux-kernel - Re: [PATCH] arm64: dts: qcom: sc7280: Enable keyboard backlight for villager

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Date:   Fri, 20 May 2022 13:29:37 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH] arm64: dts: qcom: sc7280: Enable keyboard backlight for
 villager

On Fri, May 20, 2022 at 12:57:50PM -0700, Doug Anderson wrote:
> Hi,
> 
> On Fri, May 20, 2022 at 12:48 PM Matthias Kaehlcke <mka@...omium.org> wrote:
> >
> > Villager has a backlit keyboard, enable support for the backlight.
> >
> > Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> > ---
> >
> >  arch/arm64/boot/dts/qcom/sc7280-herobrine-villager-r0.dts | 8 ++++++++
> >  arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi            | 2 +-
> >  2 files changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/boot/dts/qcom/sc7280-herobrine-villager-r0.dts b/arch/arm64/boot/dts/qcom/sc7280-herobrine-villager-r0.dts
> > index d3d6ffad4eff..b6a6a1454883 100644
> > --- a/arch/arm64/boot/dts/qcom/sc7280-herobrine-villager-r0.dts
> > +++ b/arch/arm64/boot/dts/qcom/sc7280-herobrine-villager-r0.dts
> > @@ -58,6 +58,10 @@ &ap_sar_sensor1 {
> >         status = "okay";
> >  };
> >
> > +&keyboard_backlight {
> > +       status = "okay";
> > +};
> 
> Instead of doing this, can you just get rid of the status = "disabled"
> in herobrine.dtsi? I don't think there's any benefit to having two
> levels of "disabled" in the herobrine device tree.

Sure.

I guess the 'disabled' status was put as a micro-optimization to avoid
probing the 'pwm-leds' driver on boards that don't have any such LEDs. In
practical terms it shouldn't really make a difference in terms of memory
or CPU.