linux-kernel - Re: [PATCH 2/8] drm/udl: Change drm_fb_helper_sys_*() calls to sys

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Message-ID: <20160422082415.GG2510@phenom.ffwll.local>
Date:	Fri, 22 Apr 2016 10:24:15 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Noralf Trønnes <noralf@...nnes.org>
Cc:	dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
	laurent.pinchart@...asonboard.com, tomi.valkeinen@...com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/8] drm/udl: Change drm_fb_helper_sys_*() calls to
 sys_*()

On Thu, Apr 21, 2016 at 08:18:48PM +0200, Noralf Trønnes wrote:
> 
> Den 21.04.2016 09:28, skrev Daniel Vetter:
> >On Wed, Apr 20, 2016 at 08:15:30PM +0200, Noralf Trønnes wrote:
> >>Den 20.04.2016 19:42, skrev Daniel Vetter:
> >>>On Wed, Apr 20, 2016 at 05:25:23PM +0200, Noralf Trønnes wrote:
> >>>>Now that drm_fb_helper gets deferred io support, the
> >>>>drm_fb_helper_sys_{fillrect,copyarea,imageblit} functions will schedule
> >>>>the worker that calls the deferred_io callback. This will break this
> >>>>driver so use the sys_{fillrect,copyarea,imageblit} functions directly.
> >>>>
> >>>>Signed-off-by: Noralf Trønnes <noralf@...nnes.org>
> >>>I think this intermediately breaks the build, if you disable fbdev
> >>>support. That's now supported in the fbdev helpers core generically across
> >>>all drivers.
> >>>
> >>>Not sure how to best fix this up, since the only way would be to squash
> >>>these patches, plus generic deferred io plus the conversion patches for
> >>>udl/qxl all into one. Tricky.
> >>Yes you're right, I missed that.
> >>How about this:
> >>#ifdef CONFIG_FB
> >>         sys_fillrect(info, rect);
> >>#endif
> >>
> >>The later patch will then remove this ugliness...
> >Yeah I think we have to bite the bullet and take this temporary ugliness
> >:(
> 
> Turns out the #ifdef isn't necessary since FB is always selected.
> 
> Both udl and qxl have this:
>         select DRM_KMS_HELPER
>         select DRM_KMS_FB_HELPER
> 
> And then we have:
> 
> config DRM_KMS_HELPER
>         tristate
>         depends on DRM
> 
> config DRM_KMS_FB_HELPER
>         bool
>         depends on DRM_KMS_HELPER
>         select FB
>         ...
>         select FB_SYS_FILLRECT
>         select FB_SYS_COPYAREA
>         select FB_SYS_IMAGEBLIT

Hm ... the thing that actually builds fbdev emulation is
DRM_FBDEV_EMULATION, and you can disable that. Otoh the select FB stuff
seems to be at the wrong level and probably should be moved.

But indeed I tried doing this and it's an impossible config. I guess I
need to type a patch to ditch all these selects from drivers ;-)
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch