Re: [PATCH v2 18/19] Revert "fbdev: Prevent probing generic drivers if a FB is already registered"

[Javier Martinez Canillas]

On 2/8/22 22:08, Daniel Vetter wrote:
> This reverts commit fb561bf9abde49f7e00fdbf9ed2ccf2d86cac8ee.
> 
> With
> 
> commit 27599aacbaefcbf2af7b06b0029459bbf682000d
> Author: Thomas Zimmermann <tzimmermann@xxxxxxx>
> Date:   Tue Jan 25 10:12:18 2022 +0100
> 
>     fbdev: Hot-unplug firmware fb devices on forced removal
> 
> this should be fixed properly and we can remove this somewhat hackish
> check here (e.g. this won't catch drm drivers if fbdev emulation isn't
> enabled).
>

Unfortunately this hack can't be reverted yet. Thomas' patch solves the issue
of platform devices matched with fbdev drivers to be properly unregistered if
a DRM driver attempts to remove all the conflicting framebuffers.

But the problem that fb561bf9abde ("fbdev: Prevent probing generic drivers if
a FB is already registered") worked around is different. It happens when the
DRM driver is probed before the {efi,simple}fb and other fbdev drivers, the
kicking out of conflicting framebuffers already happened and these drivers
will be allowed to probe even when a DRM driver is already present.

We need a clearer way to prevent it, but can't revert fb561bf9abde until that.

Best regards,
-- 
Javier Martinez Canillas
Linux Engineering
Red Hat