Re: [PATCH 03/11] drm: of: drm_of_find_panel_or_bridge: prioritize the bridge, not the panel

[Maxime Ripard]

On Mon, Aug 17, 2026 at 02:23:05PM +0200, Luca Ceresoli wrote:
> > That being said, if we do create a panel_bridge for every panel, why do
> > we still need drm_of_find_panel_or_bridge()? We'll only really need
> > of_drm_find_bridge(), no?
> 
> Yes, in the long term we can get rid of drm_of_find_panel_or_bridge(), but
> not in the short term due to the above mentioned drivers, and others which
> use it in "creative" ways.
> 
> The point is about the transition. This patch was an attempt to convert at
> once all the many drivers which use the most common pattern:
> 
>       | drm_of_find_panel_or_bridge(..., &panel, &bridge);
>       | if (panel)
>       |     bridge = drm_panel_bridge_add();
> 
> to then fix manually the remaining drivers (patches 6-11).
> 
> But this approach doesn't fly due to the legacy users of
> drm_of_find_panel_or_bridge() as mentioned above.
> 
> So what about this other approach instead:
> 
>  1. leave drm_of_find_panel_or_bridge() as is (it's already deprecated anyway)
>  2. keep patch 5 (which "breaks" mayt drivers which would create an additional
>     panel_bridge)
>  3. perhaps add a warning when an additional bridge is created for the
>     some panel
>  4. *in the same series*, manually convert *all* drivers to use
>     of_drm_find_bridge() or of_drm_get_bridge_by_endpoint() -- like patches
>     6-11, but done on all drivers
>  5. apply the series atomically, because it wouldn't be bisectable between
>     items 2 and 4
> 
> Your opinion?

If we look at the drivers causing us troubles, fsl-ldb, samsung-dsim,
tc358767 and waveshare-dsi can be converted directly to
devm_drm_of_get_bridge().

mcde-dsi is a mess and would be hard to fix indeed, but since it's the
only really troublesome one, maybe we can just duplicate the code in the
driver and drop / rewrite the common code however we see fit.

Maxime

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