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From: Douglas Anderson <>
To: Andrzej Hajda <>,
	Neil Armstrong <>,
	Laurent Pinchart <>,
	Jonas Karlman <>, Sam Ravnborg <>
Cc: Maarten Lankhorst <>,,
	Bjorn Andersson <>,
	Thierry Reding <>,
	Stanislav Lisovskiy <>,
	Lyude Paul <>, Stephen Boyd <>,
	Steev Klimaszewski <>,
	Linus W <>,,,
	Douglas Anderson <>,
	Rob Herring <>, Daniel Vetter <>,
	David Airlie <>, Rob Herring <>,,
Subject: [PATCH v10 02/11] dt-bindings: drm: Introduce the DP AUX bus
Date: Fri, 11 Jun 2021 10:17:38 -0700	[thread overview]
Message-ID: <20210611101711.v10.2.Id3c048d22e72a9f90084a543b5b4e3f43bc9ab62@changeid> (raw)
In-Reply-To: <>

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

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].


Signed-off-by: Douglas Anderson <>
Reviewed-by: Rob Herring <>
Reviewed-by: Linus Walleij <>

(no changes since v9)

Changes in v9:
- Commit message now notes aux-bus yaml won't have an "Example".

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

diff --git a/Documentation/devicetree/bindings/display/dp-aux-bus.yaml b/Documentation/devicetree/bindings/display/dp-aux-bus.yaml
new file mode 100644
index 000000000000..5e4afe9f98fb
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/dp-aux-bus.yaml
@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+title: DisplayPort AUX bus
+  - Douglas Anderson <>
+  DisplayPort controllers provide a control channel to the sinks that
+  are hooked up to them. This is the DP AUX bus. Over the DP AUX bus
+  we can query properties about a sink and also configure it. In
+  particular, DP sinks support DDC over DP AUX which allows tunneling
+  a standard I2C DDC connection over the AUX channel.
+  To model this relationship, DP sinks should be placed as children
+  of the DP controller under the "aux-bus" node.
+  At the moment, this binding only handles the eDP case. It is
+  possible it will be extended in the future to handle the DP case.
+  For DP, presumably a connector would be listed under the DP AUX
+  bus instead of a panel.
+  $nodename:
+    const: "aux-bus"
+  panel:
+    $ref: panel/panel-common.yaml#
+additionalProperties: false
+  - panel

  parent reply	other threads:[~2021-06-11 17:19 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-11 17:17 [PATCH v10 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus Douglas Anderson
2021-06-11 17:17 ` [PATCH v10 01/11] dt-bindings: display: simple: List hpd properties in panel-simple Douglas Anderson
2021-06-11 17:17 ` Douglas Anderson [this message]
2021-06-11 17:17 ` [PATCH v10 03/11] dt-bindings: drm/bridge: ti-sn65dsi86: Add aux-bus child Douglas Anderson
2021-06-11 17:17 ` [PATCH v10 04/11] drm: Introduce the DP AUX bus Douglas Anderson
2021-06-11 17:17 ` [PATCH v10 05/11] drm/panel: panel-simple: Allow panel-simple be a DP AUX endpoint device Douglas Anderson
2021-06-11 17:17 ` [PATCH v10 06/11] drm/panel: panel-simple: Stash DP AUX bus; allow using it for DDC Douglas Anderson
2021-06-11 17:17 ` [PATCH v10 07/11] drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev Douglas Anderson
2021-06-11 17:17 ` [PATCH v10 08/11] drm/bridge: ti-sn65dsi86: Add support for the DP AUX bus Douglas Anderson
2021-06-11 17:17 ` [PATCH v10 09/11] drm/bridge: ti-sn65dsi86: Don't read EDID blob over DDC Douglas Anderson
2021-06-11 17:17 ` [PATCH v10 10/11] drm/bridge: ti-sn65dsi86: Improve probe errors with dev_err_probe() Douglas Anderson
2021-06-11 17:17 ` [PATCH v10 11/11] arm64: dts: qcom: sc7180-trogdor: Move panel under the bridge chip Douglas Anderson
2021-06-11 19:37 ` [PATCH v10 00/11] drm: Fix EDID reading on ti-sn65dsi86 by introducing the DP AUX bus Doug Anderson

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