[PATCH] drm/fb-helper: Remove drm_fb_helper_unprepare() from drm_fb_helper_fini()

[Javier Martinez Canillas]

Thomas Zimmermann <tzimmermann at suse.de> writes:

> Move drm_fb_helper_unprepare() from drm_fb_helper_fini() into the
> calling fbdev implementation. Avoids a possible stale mutex with
> generic fbdev code.
>
> As indicated by its name, drm_fb_helper_prepare() prepares struct
> drm_fb_helper before setting up the fbdev support with a call to
> drm_fb_helper_init(). In legacy fbdev emulation, this happens next
> to each other. If successful, drm_fb_helper_fini() later tear down
> the fbdev device and also unprepare via drm_fb_helper_unprepare().
>
> Generic fbdev emulation prepares struct drm_fb_helper immediately
> after allocating the instance. It only calls drm_fb_helper_init()
> as part of processing a hotplug event. If the hotplug-handling fails,
> it runs drm_fb_helper_fini(). This unprepares the fb-helper instance
> and the next hotplug event runs on stale data.
>
> Solve this by moving drm_fb_helper_unprepare() from drm_fb_helper_fini()
> into the fbdev implementations. Call it right before freeing the
> fb-helper instance.
>
> Fixes: 4825797c36da ("drm/fb-helper: Introduce drm_fb_helper_unprepare()")

I think this should be Fixes: 032116bbe152 ("drm/fbdev-generic: Minimize
client unregistering") instead? Because commit 4825797c36da just added a
wrapper function for mutex_destroy(&fb_helper->lock), but it was commit
032116bbe152 that made drm_fbdev_cleanup() to call that helper function.

> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> Cc: Javier Martinez Canillas <javierm at redhat.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Maxime Ripard <mripard at kernel.org>
> Cc: David Airlie <airlied at gmail.com>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: dri-devel at lists.freedesktop.org
>
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
> ---

The change itself looks good to me.

Reviewed-by: Javier Martinez Canillas <javierm at redhat.com>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat