Re: [PATCH 28/37] drm/mipi-dsi: turn DRM_MIPI_DSI into a tristate

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Medium] Missing module_exit() routine in drm_mipi_dsi.c
- [Low] Linker error due to IS_ENABLED(CONFIG_DRM_MIPI_DSI) evaluating to true when built as a module
--

commit 980deb1ce9940525b50bf77a81377ee0a4c56aad
Author: Luca Ceresoli <luca.ceresoli@bootlin.com>

drm/mipi-dsi: turn DRM_MIPI_DSI into a tristate

This commit converts the DRM_MIPI_DSI configuration option from a boolean
to a tristate, allowing it to be built as a loadable module. This also
enables other tristate modules to depend on it when it is built as a module.

> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index e730e04447418..6a14bb03607a7 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -43,7 +43,7 @@ config DRM_MIPI_DBI
>  	select DRM_KMS_HELPER
>  
>  config DRM_MIPI_DSI
> -	bool
> +	tristate

Since DRM_MIPI_DSI can now be built as a module, does drm_mipi_dsi.c
need a module_exit() routine?

Currently, drm_mipi_dsi.c uses postcore_initcall(mipi_dsi_bus_init) but does
not define a corresponding module_exit() function to unregister the bus.
Without this, the module will be permanently pinned in memory after loading
and cannot be unloaded.

Could this change also cause a linker regression if CONFIG_DRM=y and
CONFIG_DRM_MIPI_DSI=m?

Core DRM code like drm_of.c uses IS_ENABLED(CONFIG_DRM_MIPI_DSI) to
conditionally compile drm_of_get_dsi_bus(). IS_ENABLED() evaluates to true
for both y and m.

If DRM is built-in and MIPI_DSI is a module, drm_of.c will compile
drm_of_get_dsi_bus(), which calls of_find_mipi_dsi_host_by_node(). This
function is exported by the drm_mipi_dsi module, so it won't be present in
vmlinux, resulting in an undefined reference.

Does the Kconfig dependency need to be adjusted, or should
IS_REACHABLE(CONFIG_DRM_MIPI_DSI) be used instead to avoid this?

>  	depends on DRM
>  
>  config DRM_KMS_HELPER

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260519-drm-bridge-hotplug-v1-0-45e2bdb3dfb4@bootlin.com?part=28