linux-kernel - Re: [PATCH] drm/amdgpu/display: initialize the variable 'i'

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Message-ID: <20210222234457.GA36153@24bbad8f3778>
Date:   Mon, 22 Feb 2021 16:44:57 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Simon Ser <contact@...rsion.fr>
Cc:     Souptick Joarder <jrdr.linux@...il.com>, harry.wentland@....com,
        sunpeng.li@....com, alexander.deucher@....com,
        christian.koenig@....com, airlied@...ux.ie, daniel@...ll.ch,
        nicholas.kazlauskas@....com, Rodrigo.Siqueira@....com,
        aurabindo.pillai@....com, stylon.wang@....com,
        bas@...nieuwenhuizen.nl, Bhawanpreet.Lakha@....com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/amdgpu/display: initialize the variable 'i'

On Mon, Feb 22, 2021 at 11:05:17PM +0000, Simon Ser wrote:
> On Monday, February 22nd, 2021 at 8:25 PM, Souptick Joarder <jrdr.linux@...il.com> wrote:
> 
> > >> drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:9804:38:
> > >> warning: variable 'i' is uninitialized when used here
> > >> [-Wuninitialized]
> >                            timing  = &edid->detailed_timings[i];
> >                                                              ^
> >    drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:9714:7:
> > note: initialize the variable 'i' to silence this warning
> >            int i;
> >                 ^
> >                  = 0
> >    1 warning generated.
> >
> > Initialize the variable 'i'.
> 
> Hm, I see this variable already initialized in the loop:
> 
>     for (i = 0; i < 4; i++) {
> 
> This is the branch agd5f/drm-next.

That is in the

	if (amdgpu_dm_connector->dc_sink->sink_signal == SIGNAL_TYPE_DISPLAY_PORT
		|| amdgpu_dm_connector->dc_sink->sink_signal == SIGNAL_TYPE_EDP) {

branch not the

	} else if (edid && amdgpu_dm_connector->dc_sink->sink_signal == SIGNAL_TYPE_HDMI_TYPE_A) {

branch, where i is indeed used uninitialized like clang complains about.

I am not at all familiar with the code so I cannot say if this fix is
the proper one but it is definitely a legitimate issue.

Cheers,
Nathan

> > Reported-by: kernel test robot <lkp@...el.com>
> > Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>
> > ---
> >  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > index a22a53d..e96d3d9 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > @@ -9717,7 +9717,7 @@ static bool parse_hdmi_amd_vsdb(struct amdgpu_dm_connector *aconnector,
> >  void amdgpu_dm_update_freesync_caps(struct drm_connector *connector,
> >  					struct edid *edid)
> >  {
> > -	int i;
> > +	int i = 0;
> >  	struct detailed_timing *timing;
> >  	struct detailed_non_pixel *data;
> >  	struct detailed_data_monitor_range *range;
> > --
> > 1.9.1