linux-kernel - Re: [PATCH 2/2] arm64: dts: qcom: sm8650: Add support for Oneplus Pad Pro (caihong)

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Message-ID: <20250602134431.114469-1-mitltlatltl@gmail.com>
Date: Mon,  2 Jun 2025 21:44:30 +0800
From: Pengyu Luo <mitltlatltl@...il.com>
To: konrad.dybcio@....qualcomm.com
Cc: andersson@...nel.org,
	conor+dt@...nel.org,
	devicetree@...r.kernel.org,
	konradybcio@...nel.org,
	krzk+dt@...nel.org,
	linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	mitltlatltl@...il.com,
	robh@...nel.org
Subject: Re: [PATCH 2/2] arm64: dts: qcom: sm8650: Add support for Oneplus Pad Pro (caihong)

On Tue, May 27, 2025 at 7:11 PM Konrad Dybcio <konrad.dybcio@....qualcomm.com> wrote:
> On 5/25/25 12:51 PM, Pengyu Luo wrote:
> > On Thu, May 22, 2025 at 11:05 PM Konrad Dybcio <konrad.dybcio@....qualcomm.com> wrote:
> >> On 5/21/25 10:37 AM, Pengyu Luo wrote:
> >>> On Wed, May 21, 2025 at 5:54 AM Konrad Dybcio <konrad.dybcio@....qualcomm.com> wrote:
> >>>> On 5/20/25 6:42 PM, Pengyu Luo wrote:
> >>>>> The OnePlus Pad Pro is an Android tablet based on the Qualcomm SM8650
> >>>>> platform. Its device codename is "caihong". This patch adds an initial
> >>>>> devicetree for basic functionality.
> >>
> >> [...]
> >>
> >>>>> +&i2c2 {
> >>>>> +     status = "okay";
> >>>>> +
> >>>>> +     /* secondary kinetic,ktz8866@11 */
> >>>>
> >>>> You can describe it, the driver sets some nonzero default brightness
> >>>>
> >>>
> >>> But the backlight framework won't index them, which causes sysfs
> >>> collision when the second instance is registering.
> >>
> >> Have you talked to the backlight maintainers? This shouldn't be too
> >> complex to figure out
> >
> > Last time I tried to touch ktz8866 source, the reviewer advised me to
> > add an backlight API to register the secondary devie. Since I am still
> > working on the other parts when I am free, it remains unresolved. Now
> > that you reminded me, then I tried to do it.
> >
> > https://lore.kernel.org/linux-fbdev/20250525104022.1326997-1-mitltlatltl@gmail.com/
>
> I think this should be made more generic, so that devices with e.g.
> quad backlight can be easily accommodated for too.. Perhaps you could
> do something like PLATFORM_DEVID_AUTO with incrementing suffixes and

Agree, thanks.

> make `backlight = <&foo>;` on the panel accept an array of devices
> that would be controlled together

In this way, we keep them independent, but we control every backlight
in drm_panel. The questions are the systemd and distribution(sorry, I
am just a junior, I use them). Generally, the systemd will create
serivce for every backlight sysfs. I encountered that they saved
different backlight values, even if I set the same value manually.
As for distribution, it seems that only half backlight is controlled.
I encountered that only half backlight got dimmed.

Best wishes,
Pengyu