[PATCH 1/2] drm/kms: Duct-tape for mode object lifetime checks

[Daniel Vetter]

On Tue, Sep 17, 2019 at 04:48:51PM +0200, Michel Dänzer wrote:
> On 2019-09-17 2:09 p.m., Daniel Vetter wrote:
> > commit 4f5368b5541a902f6596558b05f5c21a9770dd32
> > Author: Daniel Vetter <daniel.vetter at ffwll.ch>
> > Date:   Fri Jun 14 08:17:23 2019 +0200
> > 
> >     drm/kms: Catch mode_object lifetime errors
> > 
> > uncovered a bit a mess in dp drivers. Most drivers (from a quick look,
> > all except i915) register all the dp stuff in their init code, which
> > is too early. With CONFIG_DRM_DP_AUX_CHARDEV this will blow up,
> > because drm_dp_aux_register tries to add a child to a device in sysfs
> > (the connector) which doesn't even exist yet.
> > 
> > No one seems to have cared thus far. But with the above change I also
> > moved the setting of dev->registered after the ->load callback, in an
> > attempt to keep old drivers from hitting any WARN_ON backtraces. But
> > that moved radeon.ko from the "working, by accident" to "now also
> > broken" category.
> > 
> > Since this is a huge mess I figured a revert would be simplest. But
> > this check has already caught issues in i915:
> > 
> > commit 1b9bd09630d4db4827cc04d358a41a16a6bc2cb0
> > Author: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > Date:   Tue Aug 20 19:16:57 2019 +0300
> > 
> >     drm/i915: Do not create a new max_bpc prop for MST connectors
> > 
> > Hence I'd like to retain it. Fix the radeon regression by moving the
> > setting of dev->registered back to were it was, and stop the
> > backtraces with an explicit check for dev->driver->load.
> > 
> > Everyone else will stay as broken with CONFIG_DRM_DP_AUX_CHARDEV. The
> > next patch will improve the kerneldoc and add a todo entry for this.
> > 
> > Fixes: 4f5368b5541a ("drm/kms: Catch mode_object lifetime errors")
> > Cc: Sean Paul <sean at poorly.run>
> > Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> > Reported-by: Michel Dänzer <michel at daenzer.net>
> > Cc: Michel Dänzer <michel at daenzer.net>
> > Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> 
> Reviewed-by: Michel Dänzer <mdaenzer at redhat.com>
> Tested-by: Michel Dänzer <mdaenzer at redhat.com>

Thanks, merged into drm-misc-next-fixes.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch