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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 24 Dec 2020 14:28:07 -0800
Message-ID: <CAHk-=whf+kw=YSDbmvgiSvNL9ckHc8EpkTgZzMXu-bMw941GYQ@mail.gmail.com>
Subject: Re: [git pull] drm fixes for 5.11-rc1
To:     Dave Airlie <airlied@gmail.com>, Josip Pavic <Josip.Pavic@amd.com>,
        Bindu Ramamurthy <bindu.r@amd.com>,
        Alex Deucher <alexander.deucher@amd.com>
Cc:     Daniel Vetter <daniel.vetter@ffwll.ch>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Wed, Dec 23, 2020 at 6:29 PM Dave Airlie <airlied@gmail.com> wrote:
>
> Xmas eve pull request present. Just some fixes that trickled in this
> past week. Mostly amdgpu fixes, with a dma-buf/mips build fix and some
> misc komeda fixes.

Well, I already pulled and pushed out my merge, but only noticed
afterwards that clang complains about this, and I think it's a real
bug:

  drivers/gpu/drm/amd/amdgpu/../display/dc/dcn10/dcn10_mpc.c:475:6: warning:
     variable 'val' is used uninitialized whenever 'if' condition is
false [-Wsometimes-uninitialized]

and it sure is true: the code literally does

        uint32_t val;

        if (opp_id < MAX_OPP && REG(MUX[opp_id]))
                REG_GET(MUX[opp_id], MPC_OUT_MUX, &val);

        return val;

so clearly 'val' isn't initialized if that if-statement isn't true.

I assume 'opp_id' is always presumed to be valid, but that code really
is disgusting.

Just make it return 0 (or whatever) for invalid, possibly together
with a WARN_ON_ONCE(). Ok?

             Linus