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From:   Vasily Khoruzhick <anarsoul@gmail.com>
Date:   Fri, 17 May 2019 08:25:53 -0700
Message-ID: <CA+E=qVcpMeFfC0EEZRpp3Hc_yBGFMv6cGKGSQENpUTw_ZH7UwQ@mail.gmail.com>
Subject: Re: [PATCH 4/4] arm64: DTS: allwinner: a64: enable ANX6345 bridge on Teres-I
To:     Torsten Duwe <duwe@lst.de>
Cc:     Maxime Ripard <maxime.ripard@bootlin.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Chen-Yu Tsai <wens@csie.org>,
        Andrzej Hajda <a.hajda@samsung.com>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Icenowy Zheng <icenowy@aosc.io>,
        Sean Paul <seanpaul@chromium.org>,
        Harald Geyer <harald@ccbib.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        devicetree <devicetree@vger.kernel.org>,
        arm-linux <linux-arm-kernel@lists.infradead.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
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On Fri, May 17, 2019 at 2:47 AM Torsten Duwe <duwe@lst.de> wrote:
>
> On Fri, May 17, 2019 at 11:08:45AM +0200, Maxime Ripard wrote:
> > >
> > > So for all current practical purposes, we can assume the Teres-I panel
> > > to be powered properly and providing valid EDID; nothing to worry about
> > > in software.
> >
> > You're creating a generic binding for all the users of that bridge,
> > while considering only the specific case of the Teres-I.
>
> All I'm saying is that _this_ usage is also valid. Nothing keeps other
> users from defining the output panel; on the contrary: the driver at hand
> already considers an _optional_ panel and handles it, conditionally. So
> driver and binding spec are 100% in sync here.

Well, endpoint is not necessarily a panel. It can be another bridge or
connector - that's why panel can be optional in driver. But it don't
think that you can just omit an endpoint.

> This is much more straightforward than requiring an output and making up
> some dummy code and params because it cannot reasonably be handled.
> (Remember, if there is an output, the driver will make calls to the
> "attached device" driver.)

They aren't dummy. Moreover you have to attach backlight somewhere (to
panel) so it can be disabled when output is disabled.

Try 'xrandr --output eDP-1 --off' on teres with your current code and
see that backlight stays on.

>
>         Torsten
>