Re: [git pull] drm fixes for 5.11-rc1

[Linus Torvalds]

On Wed, Dec 23, 2020 at 6:29 PM Dave Airlie <airlied@xxxxxxxxx> 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