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From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Jani Nikula <jani.nikula@intel.com>,
	intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org,
	kbuild@01.org, kbuild-all@01.org
Subject: Re: drivers/gpu/drm/i915/display/intel_display.c:3934 skl_plane_stride() error: testing array offset 'color_plane' after use.
Date: Mon, 16 Sep 2019 15:43:40 +0300	[thread overview]
Message-ID: <20190916124340.GF1208@intel.com> (raw)
In-Reply-To: <20190916075913.GZ20699@kadam>

On Mon, Sep 16, 2019 at 10:59:13AM +0300, Dan Carpenter wrote:
> On Mon, Sep 16, 2019 at 10:31:35AM +0300, Jani Nikula wrote:
> > On Sat, 14 Sep 2019, Dan Carpenter <dan.carpenter@oracle.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@intel.com>
> > > Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> > >
> > > New smatch warnings:
> > > drivers/gpu/drm/i915/display/intel_display.c:3934 skl_plane_stride() error: testing array offset 'color_plane' after use.

The code looks fine to me. int color_plane is 0 or 1 so we know
the color_plane[] array is has enough elements. But if
fb->num_planes==1 we don't actually want to look at color_plane[1].

> > > drivers/gpu/drm/i915/display/intel_display.c:16328 intel_sanitize_encoder() error: we previously assumed 'crtc' could be null (see line 16318)

If crtc_state!=NULL then crtc!=NULL. Looks safe to me.

> > 
> > 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

-- 
Ville Syrjälä
Intel
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WARNING: multiple messages have this Message-ID (diff)
From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Jani Nikula <jani.nikula@intel.com>,
	kbuild@01.org, kbuild-all@01.org, linux-kernel@vger.kernel.org,
	Chris Wilson <chris@chris-wilson.co.uk>,
	intel-gfx@lists.freedesktop.org
Subject: Re: drivers/gpu/drm/i915/display/intel_display.c:3934 skl_plane_stride() error: testing array offset 'color_plane' after use.
Date: Mon, 16 Sep 2019 15:43:40 +0300	[thread overview]
Message-ID: <20190916124340.GF1208@intel.com> (raw)
In-Reply-To: <20190916075913.GZ20699@kadam>

On Mon, Sep 16, 2019 at 10:59:13AM +0300, Dan Carpenter wrote:
> On Mon, Sep 16, 2019 at 10:31:35AM +0300, Jani Nikula wrote:
> > On Sat, 14 Sep 2019, Dan Carpenter <dan.carpenter@oracle.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@intel.com>
> > > Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> > >
> > > New smatch warnings:
> > > drivers/gpu/drm/i915/display/intel_display.c:3934 skl_plane_stride() error: testing array offset 'color_plane' after use.

The code looks fine to me. int color_plane is 0 or 1 so we know
the color_plane[] array is has enough elements. But if
fb->num_planes==1 we don't actually want to look at color_plane[1].

> > > drivers/gpu/drm/i915/display/intel_display.c:16328 intel_sanitize_encoder() error: we previously assumed 'crtc' could be null (see line 16318)

If crtc_state!=NULL then crtc!=NULL. Looks safe to me.

> > 
> > 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

-- 
Ville Syrjälä
Intel

  reply	other threads:[~2019-09-16 12:43 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-14  4:08 drivers/gpu/drm/i915/display/intel_display.c:3934 skl_plane_stride() error: testing array offset 'color_plane' after use Dan Carpenter
2019-09-16  7:31 ` Jani Nikula
2019-09-16  7:31   ` Jani Nikula
2019-09-16  7:59   ` Dan Carpenter
2019-09-16  7:59     ` Dan Carpenter
2019-09-16 12:43     ` Ville Syrjälä [this message]
2019-09-16 12:43       ` Ville Syrjälä

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