Le 11/09/2025 à 15:09, Dmitry Baryshkov a écrit :
On Thu, Sep 11, 2025 at 02:49:59PM +0200, Miguel Gazquez wrote:
Le 11/09/2025 à 11:50, Maxime Ripard a écrit :
On Thu, Sep 11, 2025 at 10:51:06AM +0200, Miguel Gazquez wrote:
Le 10/09/2025 à 04:28, Dmitry Baryshkov a écrit :
On Tue, Sep 09, 2025 at 06:16:43PM +0200, Miguel Gazquez wrote:
From: Aradhya Bhatia <[email protected]>
Add support for DRM connector and make the driver support the older
format of attaching connectors onto the encoder->bridge->connector
chain.
This makes the driver compatible with display controller that only
supports the old format.
[Miguel Gazquez: Rebased + made driver work with or without
DRM_BRIDGE_ATTACH_NO_CONNECTOR]
What is the use case for not using DRM_BRIDGE_ATTACH_NO_CONNECTOR?
Some display controller drivers (like the tilcdc) call drm_bridge_attach
without DRM_BRIDGE_ATTACH_NO_CONNECTOR, so the bridge must support both with
and without DRM_BRIDGE_ATTACH_NO_CONNECTOR to be compatible with all display
controllers.
I'd rather convert tilcdc to use DRM_BRIDGE_ATTACH_NO_CONNECTOR then.
The problem is that doing that break devicetrees using the tilcdc and a
bridge who doesn't support DRM_BRIDGE_ATTACH_NO_CONNECTOR (there are
multiple bridges that don't support DRM_BRIDGE_ATTACH_NO_CONNECTOR), and if
my understanding is correct breaking devicetrees is not allowed.
How does it break devicetree? The drm_bridge_connector isn't a part of
DT.
In the current situation, a board could have the tilcdc linked with a
bridge that does not support DRM_BRIDGE_ATTACH_NO_CONNECTOR (for
example, the analogix-anx6345) , and everything will work fine.
If we convert the tilcdc to always use DRM_BRIDGE_ATTACH_NO_CONNECTOR,
that same configuration will stop working.
When I said "breaking devicetree" I meant that a devicetree describing
this setup would no longer produce a working system, not that the DT
files or bindings themselves are incorrect.
I didn't find any upstream dts with this configuration, but maybe there
is some out-of-tree dts which would be affected.
As far as I understand, we should avoid that.
On top of that, having the it66121 handle both cases makes it compatible
with display controllers that don’t use DRM_BRIDGE_ATTACH_NO_CONNECTOR,
which are still fairly common.
--
Miguel Gazquez, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
