[PATCH 3/4] drm/fb-helper: Add module option to disable fbdev emulation

[Daniel Vetter]

On Wed, Aug 26, 2015 at 01:34:58PM +0200, Daniel Vetter wrote:
> On Wed, Aug 26, 2015 at 02:14:37PM +0530, Archit Taneja wrote:
> > 
> > 
> > On 08/26/2015 10:42 AM, Archit Taneja wrote:
> > >
> > >
> > >On 08/25/2015 07:15 PM, Daniel Vetter wrote:
> > >>Faster than recompiling.
> > >>
> > >>Note that restore_fbdev_mode_unlocked is a bit special and the only
> > >>one which returns an error code when fbdev isn't there - i915 needs
> > >>that one to not fall over with some additional fbcon related restore
> > >>code. Everyone else just ignores the return value or only prints a
> > >>DRM_DEBUG level message.
> > >
> > >Reviewed-by:Archit Taneja <architt at codeaurora.org>
> > 
> > 
> > With the module param, and the drivers should see the following state(
> > based on the truth table below):
> > 
> > module param | config option
> >    true      |    true       -> real helper funcs called, driver
> >                                 allocated drm_fb_helper is correctly
> >                                 populated.
> > 
> >    false     |    true       -> real helper funcs called, but bailed
> >                                 out early, driver allocated
> >                                 drm_fb_helper is non-NULL, but we won't
> >                                 end up using it.
> 
> Hm I tried to give drivers the same semantics here as with the stub
> functions. Where did I screw up? The goal really was to match the end
> result for drivers ...

Note that at least for i915 we can't make it perfectly equal since i915
compiles out a few more things with FBDEV_EMULATION=n than just the stubs.
Long-term we might want to push some of that into helpers too perhaps.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch