Re: [PATCH RESEND v2 06/25] drm/fb_helper: Create a wrapper for remove_conflicting_framebuffers

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Jul 28, 2015 at 08:46:24PM +0200, Daniel Vetter wrote:
> On Wed, Jul 22, 2015 at 02:58:01PM +0530, Archit Taneja wrote:
> > Some drm drivers call remove_conflicting_framebuffers. Create a
> > drm_fb_helper function that wraps around these calls.
> > 
> > This is part of an effort to prevent drm drivers from calling fbdev
> > functions directly, in order to make fbdev emulation a top level drm
> > option.
> > 
> > v2:
> > - Added kerneldocs
> > - Follow the drm way of aligning of arguments in func definitions
> > 
> > Signed-off-by: Archit Taneja <architt@codeaurora.org>
> > ---
> >  drivers/gpu/drm/drm_fb_helper.c | 15 +++++++++++++++
> >  include/drm/drm_fb_helper.h     |  4 ++++
> >  2 files changed, 19 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> > index 9620aa5..86e4e2c 100644
> > --- a/drivers/gpu/drm/drm_fb_helper.c
> > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > @@ -894,6 +894,21 @@ void drm_fb_helper_set_suspend(struct drm_fb_helper *fb_helper, int state)
> >  }
> >  EXPORT_SYMBOL(drm_fb_helper_set_suspend);
> >  
> > +/**
> > + * drm_fb_helper_remove_conflicting_framebuffers - wrapper around
> > + *						remove_conflicting_framebuffers
> > + * @fb_helper: driver-allocated fbdev helper
> > + *
> > + * A wrapper around remove_conflicting_framebuffers implemented by fbdev core
> > + */
> > +int drm_fb_helper_remove_conflicting_framebuffers(struct apertures_struct *a,
> > +						  const char *name,
> > +						  bool primary)
> > +{
> > +	return remove_conflicting_framebuffers(a, name, primary);
> > +}
> > +EXPORT_SYMBOL(drm_fb_helper_remove_conflicting_framebuffers);
> 
> Chris Wilson reported on irc that if he builds with I915_FBDEV=n then
> there's a missing symbol problem here because i915 wants to kick out other
> framebuffers (well we have to for correctness) even when fbdev emulation
> is disabled. If you look at i915_dma.c you'll see that the call to
> remove_conflicting_framebuffers is conditional upon CONFIG_FB and not
> CONFIG_I915_FBDEV.
> 
> I think the proper solution here would be to provide a static inline
> helper for remove_conflicting_framebuffer itself when CONFIG_FB=n, since a
> all drivers who call this still want to call this even when fbdev
> emulation is disabled.
> 
> Plan B would be to move this into core drm and make the static inline one
> selected for CONFIG_FB=n. If you do that then maybe also rename it to
> drm_remove_conflicting_framebuffer since this really is only tangetial to
> fbdev emulation.
> 
> Anyway current patch unfortunately won't work since we really must remove
> other framebuffers even in the FB=y, I915_FBDEV=n case. So I dropped it
> from drm-misc for now. Unfortunately that means all the driver conversions
> won't apply anymore either :(

Ok I didn't have to drop all of the driver specific patches since all the
arm ones don't have calls to remove_conflicting_framebuffers.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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