fbdev: Fix unregistering of framebuffers without device

[Sudip Mukherjee]

On Mon, Apr 04, 2022 at 09:44:02PM +0200, Thomas Zimmermann wrote:
> OF framebuffers do not have an underlying device in the Linux
> device hierarchy. Do a regular unregister call instead of hot
> unplugging such a non-existing device. Fixes a NULL dereference.
> An example error message on ppc64le is shown below.
> 

<snip>

> 
> Tested with 5.17 on qemu ppc64le emulation.
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
> Fixes: 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal")
> Reported-by: Sudip Mukherjee <sudipm.mukherjee at gmail.com>
> Cc: Zack Rusin <zackr at vmware.com>
> Cc: Javier Martinez Canillas <javierm at redhat.com>
> Cc: Hans de Goede <hdegoede at redhat.com>
> Cc: stable at vger.kernel.org # v5.11+
> Cc: Helge Deller <deller at gmx.de>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Sam Ravnborg <sam at ravnborg.org>
> Cc: Zheyu Ma <zheyuma97 at gmail.com>
> Cc: Xiyu Yang <xiyuyang19 at fudan.edu.cn>
> Cc: Zhen Lei <thunder.leizhen at huawei.com>
> Cc: Matthew Wilcox <willy at infradead.org>
> Cc: Alex Deucher <alexander.deucher at amd.com>
> Cc: Tetsuo Handa <penguin-kernel at i-love.sakura.ne.jp>
> Cc: Guenter Roeck <linux at roeck-us.net>
> Cc: linux-fbdev at vger.kernel.org
> Cc: dri-devel at lists.freedesktop.org
> Link: https://lore.kernel.org/all/YkHXO6LGHAN0p1pq@debian/ # [1]
> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> ---

Tested-by: Sudip Mukherjee <sudip.mukherjee at codethink.co.uk>

--
Regards
Sudip