Messages in this thread | | | From | Arvind Sankar <> | Date | Thu, 6 Feb 2020 18:12:13 -0500 | Subject | Re: Error building v5.5-git on PowerPC32 - bisected to commit 7befe621ff81 |
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On Thu, Feb 06, 2020 at 04:46:52PM -0600, Larry Finger wrote: > When building post V5.5 on my PowerBook G4 Aluminum, the build failed with the > following error: > > drivers/gpu/drm/drm_edid.c: In function ‘cea_mode_alternate_timings’: > drivers/gpu/drm/drm_edid.c:3275:2: error: call to ‘__compiletime_assert_3282’ > declared with attribute error: BUILD_BUG_ON failed: cea_mode_for_vic(8)->vtotal > != 262 || cea_mode_for_vic(9)->vtotal != 262 || cea_mode_for_vic(12)->vtotal != > 262 || cea_mode_for_vic(13)->vtotal != 262 || cea_mode_for_vic(23)->vtotal != > 312 || cea_mode_for_vic(24)->vtotal != 312 || cea_mode_for_vic(27)->vtotal != > 312 || cea_mode_for_vic(28)->vtotal != 312 > > This error was bisected to commit 7befe621ff81 ("drm/edid: Abstract away > cea_edid_modes[]"). > > This problem is clearly a problem with the gcc compiler on the box, namely gcc > (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3. I had no success finding why the > attributes were wrong, and finally settled on the following hack: > > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c > index 99769d6c9f84..062bbe2b254a 100644 > --- a/drivers/gpu/drm/drm_edid.c > +++ b/drivers/gpu/drm/drm_edid.c > @@ -3272,6 +3272,7 @@ cea_mode_alternate_timings(u8 vic, struct drm_display_mode > *mode) > * get the other variants by simply increasing the > * vertical front porch length. > */ > +#ifndef CONFIG_PPC32 > BUILD_BUG_ON(cea_mode_for_vic(8)->vtotal != 262 || > cea_mode_for_vic(9)->vtotal != 262 || > cea_mode_for_vic(12)->vtotal != 262 || > @@ -3280,6 +3281,7 @@ cea_mode_alternate_timings(u8 vic, struct drm_display_mode > *mode) > cea_mode_for_vic(24)->vtotal != 312 || > cea_mode_for_vic(27)->vtotal != 312 || > cea_mode_for_vic(28)->vtotal != 312); > +#endif > > if (((vic == 8 || vic == 9 || > vic == 12 || vic == 13) && mode->vtotal < 263) || > > Disabling the build check allows me to build and test the post v5.5 versions. > > Larry
It's not that the attributes are wrong. The problem is that BUILD_BUG_ON requires a compile-time evaluatable condition. gcc-4.6 is apparently not good enough at optimizing to reduce that expression to a constant, though it was able to do it with the array accesses.
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