[PATCH 3/3] drm: Track framebuffer references at the point of assignment

[Daniel Vetter]

On Mon, Nov 28, 2016 at 08:46:11AM +0000, Chris Wilson wrote:
> On Mon, Nov 28, 2016 at 08:48:34AM +0100, Daniel Vetter wrote:
> > On Fri, Nov 25, 2016 at 03:32:31PM +0000, Chris Wilson wrote:
> > > --- a/drivers/gpu/drm/drm_atomic.c
> > > +++ b/drivers/gpu/drm/drm_atomic.c
> > > @@ -1253,7 +1253,7 @@ drm_atomic_set_fb_for_plane(struct drm_plane_state *plane_state,
> > >  		DRM_DEBUG_ATOMIC("Set [NOFB] for plane state %p\n",
> > >  				 plane_state);
> > >  
> > > -	drm_framebuffer_assign(&plane_state->fb, fb);
> > > +	drm_framebuffer_assign(__mkwrite_drm_framebuffer(&plane_state->fb), fb);
> > 
> > Feels like const gone the wrong way round? Or I'm not entirely clear on
> > what this is supposed to achieve. Just dropping the const would still be a
> > nice improvement.
> 
> No one is supposed to be writing to it. Adding the const generates a
> compiler warning for incorrect code that doesn't do the refcounting -
> but doesn't generate a warning for anything simply checking the value.
> It is the moral equivalent to calling it _fb to catch all the users.

But then shouldn't all users use the drm_plane_set_fb helper (and that
maybe gain a comment)? The above escaped the conversion/consolidation,
which is why it looked funny to me ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch