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

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Date:   Mon, 22 Feb 2021 23:50:06 +0000
From:   Simon Ser <contact@...rsion.fr>
To:     Nathan Chancellor <nathan@...nel.org>
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 Tuesday, February 23rd, 2021 at 12:44 AM, Nathan Chancellor <nathan@...nel.org> wrote:

> 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.

I think you have an outdated branch. In my checkout, i is not used in the first
branch, and is initialized in the second one.

https://cgit.freedesktop.org/~agd5f/linux/tree/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c?h=drm-next#n9700