Re: [PATCH v8 02/11] dt-bindings: drm: Introduce the DP AUX bus

From: Rob Herring <robh@kernel.org>
To: Douglas Anderson <dianders@chromium.org>
Cc: Thierry Reding <treding@nvidia.com>,
	dri-devel@lists.freedesktop.org,
	Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>,
	Stephen Boyd <swboyd@chromium.org>,
	robdclark@chromium.org,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Daniel Vetter <daniel@ffwll.ch>, David Airlie <airlied@linux.ie>,
	Steev Klimaszewski <steev@kali.org>,
	Neil Armstrong <narmstrong@baylibre.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	Jonas Karlman <jonas@kwiboo.se>, Lyude Paul <lyude@redhat.com>,
	Sam Ravnborg <sam@ravnborg.org>,
	Linus W <linus.walleij@linaro.org>,
	linux-arm-msm@vger.kernel.org,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	Rob Herring <robh+dt@kernel.org>,
	Andrzej Hajda <a.hajda@samsung.com>
Subject: Re: [PATCH v8 02/11] dt-bindings: drm: Introduce the DP AUX bus
Date: Wed, 2 Jun 2021 13:08:13 -0500	[thread overview]
Message-ID: <20210602180813.GA3688734@robh.at.kernel.org> (raw)
In-Reply-To: <20210524165920.v8.2.Id3c048d22e72a9f90084a543b5b4e3f43bc9ab62@changeid>

On Mon, 24 May 2021 17:01:50 -0700, Douglas Anderson 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.
> 
> 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@chromium.org>
> ---
> My DT yaml-fu is still weak. If I did something stupid, please help me
> learn how to do this better!
> 
> NOTE: there is no "Example" in this bindings file. Yikes! This is
> because I wanted to keep this patch separate from the one that enables
> the first eDP controller. See the patch ("dt-bindings: drm/aux-bus:
> Add an example") for the example.
> 
> ALSO: if anyone else would like to be listed as a "Maintainer" in this
> file then please shout!
> 
> Changes in v8:
> - Separate DP AUX bus binding is new for v8.
> 
>  .../bindings/display/dp-aux-bus.yaml          | 37 +++++++++++++++++++
>  1 file changed, 37 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/dp-aux-bus.yaml
> 

Reviewed-by: Rob Herring <robh@kernel.org>