Re: [PATCH] drm/exynos: gsc: allocate formats as a flexible array member

[Rosen Penev]

On Sun, Nov 8, 2026 at 8:41 PM Inki Dae <daeinki@xxxxxxxxx> wrote:
>
> Hi,
>
> 2026년 10월 5일 (월) 오전 9:11, Rosen Penev <rosenp@xxxxxxxxx>님이 작성:
> >
> > The formats array is allocated separately with devm_kcalloc() and only
> > referenced through the gsc_context. Make it a flexible array member at
> > the end of the context and allocate both in one go with struct_size().
> >
> > Annotate it with __counted_by(num_formats) so the array accesses can be
> > bounds checked with FORTIFY_SOURCE and UBSAN_BOUNDS.
> >
> > Assisted-by: LLM
>
> The allocation and lifetime changes look reasonable to me, but
> Assisted-by: LLM causes checkpatch.pl to report a non-standard
> signature and an unrecognized email address. Please describe the AI
> assistance in the commit message prose instead.
It just wrote the description. No actual code. I'll use
devm_kzalloc_flex in the next one.
>
> Thanks,
> Inki Dae
>
> > Signed-off-by: Rosen Penev <rosenp@xxxxxxxxx>
> > ---
> >  drivers/gpu/drm/exynos/exynos_drm_gsc.c | 17 ++++++-----------
> >  1 file changed, 6 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/exynos/exynos_drm_gsc.c b/drivers/gpu/drm/exynos/exynos_drm_gsc.c
> > index d9637ddfcfc4..f1807ef664e1 100644
> > --- a/drivers/gpu/drm/exynos/exynos_drm_gsc.c
> > +++ b/drivers/gpu/drm/exynos/exynos_drm_gsc.c
> > @@ -99,7 +99,6 @@ struct gsc_context {
> >         void            *dma_priv;
> >         struct device   *dev;
> >         struct exynos_drm_ipp_task      *task;
> > -       struct exynos_drm_ipp_formats   *formats;
> >         unsigned int                    num_formats;
> >
> >         void __iomem    *regs;
> > @@ -110,6 +109,7 @@ struct gsc_context {
> >         int     id;
> >         int     irq;
> >         bool    rotation;
> > +       struct exynos_drm_ipp_formats   formats[] __counted_by(num_formats);
> >  };
> >
> >  /**
> > @@ -1222,21 +1222,19 @@ static int gsc_probe(struct platform_device *pdev)
> >         struct gsc_context *ctx;
> >         int num_formats, ret, i, j;
> >
> > -       ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
> > +       num_formats = ARRAY_SIZE(gsc_formats) + ARRAY_SIZE(gsc_tiled_formats);
> > +       ctx = devm_kzalloc(dev, struct_size(ctx, formats, num_formats), GFP_KERNEL);
> >         if (!ctx)
> >                 return -ENOMEM;
> >
> > +       ctx->num_formats = num_formats;
> > +       formats = ctx->formats;
> > +
> >         driver_data = device_get_match_data(dev);
> >         ctx->dev = dev;
> >         ctx->num_clocks = driver_data->num_clocks;
> >         ctx->clk_names = driver_data->clk_names;
> >
> > -       /* construct formats/limits array */
> > -       num_formats = ARRAY_SIZE(gsc_formats) + ARRAY_SIZE(gsc_tiled_formats);
> > -       formats = devm_kcalloc(dev, num_formats, sizeof(*formats), GFP_KERNEL);
> > -       if (!formats)
> > -               return -ENOMEM;
> > -
> >         /* linear formats */
> >         for (i = 0; i < ARRAY_SIZE(gsc_formats); i++) {
> >                 formats[i].fourcc = gsc_formats[i];
> > @@ -1256,9 +1254,6 @@ static int gsc_probe(struct platform_device *pdev)
> >                 formats[j].num_limits = driver_data->num_limits;
> >         }
> >
> > -       ctx->formats = formats;
> > -       ctx->num_formats = num_formats;
> > -
> >         /* clock control */
> >         for (i = 0; i < ctx->num_clocks; i++) {
> >                 ctx->clocks[i] = devm_clk_get(dev, ctx->clk_names[i]);
> > --
> > 2.56.0
> >
> >