Re: [PATCH 10/10] drm: of: forbid bridge-only calls to drm_of_find_panel_or_bridge()

["Luca Ceresoli" <luca.ceresoli@bootlin.com>]

Hello Dmitry, Maxime,

On Mon Apr 13, 2026 at 8:04 PM CEST, Dmitry Baryshkov wrote:
> On Mon, Apr 13, 2026 at 03:58:42PM +0200, Luca Ceresoli wrote:
>> Up to now drm_of_find_panel_or_bridge() can be called with a bridge pointer
>> only, a panel pointer only, or both a bridge and a panel pointers. The
>> logic to handle all the three cases is somewhat complex to read however.
>>
>> Now all bridge-only callers have been converted to
>> of_drm_get_bridge_by_endpoint(), which is simpler and handles bridge
>> refcounting. So forbid new bridge-only users by mandating a non-NULL panel
>> pointer in the docs and in the sanity checks along with a warning.
>
> Are there remaining users which still use either the bridge or the
> panel? Would it be possible / better to drop the two-arg version?

Yes. I counted ~20 panel+bridge and 4 panel-only callers with this series
applied, and on top of those there are devm_drm_of_get_bridge() and
drmm_of_get_bridge() which to me are the real issue because they make it
impossible to correctly handle bridge lifetime.

We discussed this with both you and Maxime a while back. AFAIK Maxime has a
plan to make every panel automatically instantiate a panel_bridge. I think
that's the only reasonable approach to get rid of
drm_of_find_panel_or_bridge() + *_of_get_bridge() and make bridge lifetime
easier and safe.

@Maxime, do you have updates on that idea?

Best regards,
Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com