linux-kernel - Re: drivers/gpu/drm/i915/display/intel_display.c:3934 skl_plane_stride() error: testing array offset 'color

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Message-ID: <20190916075913.GZ20699@kadam>
Date:   Mon, 16 Sep 2019 10:59:13 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Jani Nikula <jani.nikula@...el.com>
Cc:     kbuild@...org, kbuild-all@...org, linux-kernel@...r.kernel.org,
        Chris Wilson <chris@...is-wilson.co.uk>,
        intel-gfx@...ts.freedesktop.org,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>
Subject: Re: drivers/gpu/drm/i915/display/intel_display.c:3934
 skl_plane_stride() error: testing array offset 'color_plane' after use.

On Mon, Sep 16, 2019 at 10:31:35AM +0300, Jani Nikula wrote:
> On Sat, 14 Sep 2019, Dan Carpenter <dan.carpenter@...cle.com> wrote:
> > tree:   https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux.git master
> > head:   a7f89616b7376495424f682b6086e0c391a89a1d
> > commit: df0566a641f959108c152be748a0a58794280e0e drm/i915: move modesetting core code under display/
> > date:   3 months ago
> >
> > If you fix the issue, kindly add following tag
> > Reported-by: kbuild test robot <lkp@...el.com>
> > Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> >
> > New smatch warnings:
> > drivers/gpu/drm/i915/display/intel_display.c:3934 skl_plane_stride() error: testing array offset 'color_plane' after use.
> > drivers/gpu/drm/i915/display/intel_display.c:16328 intel_sanitize_encoder() error: we previously assumed 'crtc' could be null (see line 16318)
> 
> Odd, what changed to provoke the warnings now? Or is the smatch test
> new?
> 

It looks like the cross function DB is out of data slightly.  Maybe
because the file moved?  On my system Smatch knows that color_plane is
0-1 and plane_state->color_plane[] is a two element array so it doesn't
print the warning.

This is just a sanity check which is never triggered.  Should the sanity
check be move?  What was originally intended?  It's hard to say.

regards,
dan carpenter