Re: [PATCH v2 01/16] drm/panel: get/put panel reference in drm_panel_add/remove()

[Luca Ceresoli]

Hello Anusha,

On Thu, 19 Jun 2025 14:15:53 -0500
Anusha Srivatsa <asrivats@xxxxxxxxxx> wrote:

> Take the panel reference and put it back as required.
> drm_panel_add() and drm_panel_remove() add a panel to
> the global registry and removes a panel respectively.
> Use get() and put() helpers to keep up with refcounting.
> 
> Reviewed-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx>
> Signed-off-by: Anusha Srivatsa <asrivats@xxxxxxxxxx>

This patch is good.

I'd just point out that this must be applied only after all drivers
have been converted to the the _alloc API, otherwise with the following
sequence:

  panel = devm_kzalloc();
  drm_panel_init(panel);
  drm_panel_add(panel);
  ...
  drm_panel_remove(panel); <-----

at the drm_panel_remove() you'd have a warning:

  refcount_t: addition on 0; use-after-free.

So, if all panel drivers are converted:
Reviewed-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx>

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