linux-kernel - Re: [PATCH] drm/msm/a6xx: Fix missing ARRAY

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Date:   Sat, 5 Mar 2022 13:37:52 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Rob Clark <robdclark@...il.com>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Rob Clark <robdclark@...omium.org>,
        Sean Paul <sean@...rly.run>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Akhil P Oommen <quic_akhilpo@...cinc.com>,
        Jonathan Marek <jonathan@...ek.ca>,
        Jordan Crouse <jordan@...micpenguin.net>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm/a6xx: Fix missing ARRAY_SIZE() check

On Sat, 5 Mar 2022 at 00:57, Rob Clark <robdclark@...il.com> wrote:
>
> On Fri, Mar 4, 2022 at 1:47 PM Dmitry Baryshkov
> <dmitry.baryshkov@...aro.org> wrote:
> >
> > On Fri, 4 Mar 2022 at 23:23, Rob Clark <robdclark@...il.com> wrote:
> > >
> > > From: Rob Clark <robdclark@...omium.org>
> > >
> > > Fixes: f6d62d091cfd ("drm/msm/a6xx: add support for Adreno 660 GPU")
> > > Signed-off-by: Rob Clark <robdclark@...omium.org>
> >
> > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > However see the comment below.
> >
> > > ---
> > >  drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > > index 02b47977b5c3..6406d8c3411a 100644
> > > --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > > +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > > @@ -687,6 +687,7 @@ static void a6xx_set_cp_protect(struct msm_gpu *gpu)
> > >
> > >         BUILD_BUG_ON(ARRAY_SIZE(a6xx_protect) > 32);
> > >         BUILD_BUG_ON(ARRAY_SIZE(a650_protect) > 48);
> > > +       BUILD_BUG_ON(ARRAY_SIZE(a660_protect) > 48);
> >
> > The magic number 32 and 48 are repeated through this code. I'd suggest
> > to define them and use defined names.
> > It can come up as a separate commit.
> >
>
> Or perhaps instead:

IMO this is much better.
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

> ----
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index 6406d8c3411a..58c371930fb4 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -683,20 +683,23 @@ static void a6xx_set_cp_protect(struct msm_gpu *gpu)
>  {
>         struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
>         const u32 *regs = a6xx_protect;
> -       unsigned i, count = ARRAY_SIZE(a6xx_protect), count_max = 32;
> -
> -       BUILD_BUG_ON(ARRAY_SIZE(a6xx_protect) > 32);
> -       BUILD_BUG_ON(ARRAY_SIZE(a650_protect) > 48);
> -       BUILD_BUG_ON(ARRAY_SIZE(a660_protect) > 48);
> +       unsigned i, count, count_max;
>
>         if (adreno_is_a650(adreno_gpu)) {
>                 regs = a650_protect;
>                 count = ARRAY_SIZE(a650_protect);
>                 count_max = 48;
> +               BUILD_BUG_ON(ARRAY_SIZE(a650_protect) > 48);
>         } else if (adreno_is_a660_family(adreno_gpu)) {
>                 regs = a660_protect;
>                 count = ARRAY_SIZE(a660_protect);
>                 count_max = 48;
> +               BUILD_BUG_ON(ARRAY_SIZE(a660_protect) > 48);
> +       } else {
> +               regs = a6xx_protect;
> +               count = ARRAY_SIZE(a6xx_protect);
> +               count_max = 32;
> +               BUILD_BUG_ON(ARRAY_SIZE(a6xx_protect) > 32);
>         }
>
>         /*
> ----
>
> that moves each of the two uses of constant together..  adding three
> #defines each used only twice seems a bit silly, IMHO
>
> BR,
> -R



-- 
With best wishes
Dmitry