linux-kernel - Re: [PATCH v9 02/11] dt-bindings: drm: Introduce the DP AUX bus

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Date:   Wed, 9 Jun 2021 13:05:08 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Sam Ravnborg <sam@...nborg.org>,
        Rob Clark <robdclark@...omium.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Stanislav Lisovskiy <stanislav.lisovskiy@...el.com>,
        Steev Klimaszewski <steev@...i.org>,
        MSM <linux-arm-msm@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Thierry Reding <treding@...dia.com>,
        Lyude Paul <lyude@...hat.com>,
        "open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Rob Herring <robh@...nel.org>, Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Rob Herring <robh+dt@...nel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 02/11] dt-bindings: drm: Introduce the DP AUX bus

On Mon, Jun 7, 2021 at 7:06 PM Douglas Anderson <dianders@...omium.org> wrote:

> We want to be able to list an eDP panel as a child of an eDP
> controller node to represent the fact that the panel is connected to
> the controller's DP AUX bus. Though the panel and the controller are
> connected in several ways, the DP AUX bus is the primary control
> interface between the two and thus makes the most sense to model in
> device tree hierarchy.
>
> Listing a panel in this way makes it possible for the panel driver to
> easily get access to the DP AUX bus that it resides on, which can be
> useful to help in auto-detecting the panel and for turning on various
> bits.
>
> NOTE: historically eDP panels were _not_ listed under their controller
> but were listed at the top level of the device tree. This will still
> be supported for backward compatibility (and while DP controller
> drivers are adapted to support the new DT syntax) but should be
> considered deprecated since there is no downside to listing the panel
> under the controller.
>
> For now, the DP AUX bus bindings will only support an eDP panel
> underneath. It's possible it could be extended to allow having a DP
> connector under it in the future.
>
> NOTE: there is no "Example" in this bindings file. Yikes! This avoids
> duplicating the same example lots of places. See users of the aux bus
> (like ti-sn65dsi86) for examples.
>
> The idea for this bus's design was hashed out over IRC [1].
>
> [1] https://people.freedesktop.org/~cbrill/dri-log/?channel=dri-devel&date=2021-05-11
>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> Reviewed-by: Rob Herring <robh@...nel.org>

I overall like this approach a lot:
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij