linux-kernel - Re: [PATCH] drm/nouveau/bios: set info only when the return is not 0

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Date:   Mon, 04 Jul 2022 17:32:18 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     Tom Rix <trix@...hat.com>, bskeggs@...hat.com, kherbst@...hat.com,
        airlied@...ux.ie, daniel@...ll.ch, nathan@...nel.org,
        ndesaulniers@...gle.com
Cc:     dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] drm/nouveau/bios: set info only when the return is not 0

Reviewed-by: Lyude Paul <lyude@...hat.com>

Currently on flakey internet in the back of a car, so I probably won't be able
to push this until I get back tonight or early tomorrow

On Sat, 2022-07-02 at 11:39 -0400, Tom Rix wrote:
> clang static analysis reports
> drivers/gpu/drm/nouveau/nvkm/subdev/bios/pmu.c:68:17: warning: The right
> operand of '*' is a garbage value [core.UndefinedBinaryOperatorResult]
>         switch (!!data * *ver) {
>                        ^ ~~~~
> A switch statement with only a default should be reduced to an if.
> 
> If nvbios_pmuEp() returns 0, via the data variable, the output info
> parameter
> is not used.  So set info only when data is not 0.
> 
> The struct nvbios_pmuE only has the type and data elements.  Since both of
> these
> are explicitly set, memset is not needed.  So remove it.
> 
> Signed-off-by: Tom Rix <trix@...hat.com>
> ---
>  drivers/gpu/drm/nouveau/nvkm/subdev/bios/pmu.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/bios/pmu.c
> b/drivers/gpu/drm/nouveau/nvkm/subdev/bios/pmu.c
> index b4a308f3cf7b..49e2664a734c 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/bios/pmu.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/bios/pmu.c
> @@ -64,12 +64,9 @@ nvbios_pmuEp(struct nvkm_bios *bios, int idx, u8 *ver, u8
> *hdr,
>              struct nvbios_pmuE *info)
>  {
>         u32 data = nvbios_pmuEe(bios, idx, ver, hdr);
> -       memset(info, 0x00, sizeof(*info));
> -       switch (!!data * *ver) {
> -       default:
> +       if (data) {
>                 info->type = nvbios_rd08(bios, data + 0x00);
>                 info->data = nvbios_rd32(bios, data + 0x02);
> -               break;
>         }
>         return data;
>  }

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat