linux-kernel - Re: [PATCH] drm/nouveau/svm: remove unused ret variable

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Message-ID: <CAKwvOdnQCVZ+gqOWzsRvkSKbYFJdh5yAJEN-TT+7MC4e8tdu8A@mail.gmail.com>
Date:   Fri, 7 Apr 2023 11:01:19 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Tom Rix <trix@...hat.com>
Cc:     bskeggs@...hat.com, kherbst@...hat.com, lyude@...hat.com,
        airlied@...il.com, daniel@...ll.ch, nathan@...nel.org,
        dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] drm/nouveau/svm: remove unused ret variable

On Wed, Mar 29, 2023 at 4:14 PM Tom Rix <trix@...hat.com> wrote:
>
> clang with W=1 reports
> drivers/gpu/drm/nouveau/nouveau_svm.c:929:6: error: variable
>   'ret' set but not used [-Werror,-Wunused-but-set-variable]
>         int ret;
>             ^
> This variable is not used so remove it.
>
> Signed-off-by: Tom Rix <trix@...hat.com>
> ---
>  drivers/gpu/drm/nouveau/nouveau_svm.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
> index a74ba8d84ba7..e072d610f2f9 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_svm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
> @@ -926,15 +926,14 @@ nouveau_pfns_map(struct nouveau_svmm *svmm, struct mm_struct *mm,
>                  unsigned long addr, u64 *pfns, unsigned long npages)
>  {
>         struct nouveau_pfnmap_args *args = nouveau_pfns_to_args(pfns);
> -       int ret;
>
>         args->p.addr = addr;
>         args->p.size = npages << PAGE_SHIFT;
>
>         mutex_lock(&svmm->mutex);
>
> -       ret = nvif_object_ioctl(&svmm->vmm->vmm.object, args,
> -                               struct_size(args, p.phys, npages), NULL);
> +       nvif_object_ioctl(&svmm->vmm->vmm.object, args,
> +                         struct_size(args, p.phys, npages), NULL);

nvif_object_ioctl() may return -ENOSYS.  Seeing other call sites have
comments like:
114     /*XXX: warn? */
134     /*XXX: warn? */

or other places where the return code isn't checked makes me think
that a better approach would be to
1. plumb error codes back up through nouveau_pfns_map() (and other
call sites of nvif_object_ioctl)
2. consider making nvif_object_ioctl __must_check

>
>         mutex_unlock(&svmm->mutex);
>  }
> --
> 2.27.0
>


-- 
Thanks,
~Nick Desaulniers