Suspect code in drm_crtc_helper.c

Giovanni Campagna scampa.giovanni at gmail.com
Fri Sep 13 02:03:37 PDT 2013


Hello all

I was reading through the drm code to get an understanding of how it
works, and stumbled upon some really strange code in
drm_crtc_helper_set_config(), where it computes then new encoder for
each connector (drm_crtc_helper.c:705 in linux-next/master, aka
f03a594).
There is a comment there saying "don't break so the fail path works
correctly", but then immediately after it breaks unconditionally, also
leaving a block of code unreachable.
Btw, the break and the comment are from f453ba04 ("DRM: add mode
setting support"), while the block after is from 25f397a4
("drm/crtc-helper: explicit DPMS on after modeset")

I don't have enough knowledge of DRM internals to know if this is
correct or not, but I think I should point it out, and then you'll
know. At least, the unreachable code looks like a bug to me.

Cheers

Giovanni


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