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

[Inki Dae]

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 fimc_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
> Signed-off-by: Rosen Penev <rosenp@xxxxxxxxx>

The allocation size, initialization order, and format array lifetime
look correct to me.
checkpatch.pl reports an error for Assisted-by: LLM like below. Please
describe the AI assistance in the commit message instead of using this
trailer.

WARNING: Non-standard signature: Assisted-by:
#57:
Assisted-by: LLM

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Thanks,
Inki Dae

> ---
>  drivers/gpu/drm/exynos/exynos_drm_fimc.c | 17 +++++------------
>  1 file changed, 5 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_fimc.c b/drivers/gpu/drm/exynos/exynos_drm_fimc.c
> index 09e33a26caaf..079d24d0671c 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_fimc.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_fimc.c
> @@ -99,7 +99,6 @@ struct fimc_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;
> @@ -108,6 +107,7 @@ struct fimc_context {
>         struct fimc_scaler      sc;
>         int     id;
>         int     irq;
> +       struct exynos_drm_ipp_formats   formats[] __counted_by(num_formats);
>  };
>
>  static u32 fimc_read(struct fimc_context *ctx, u32 reg)
> @@ -1273,20 +1273,16 @@ static int fimc_probe(struct platform_device *pdev)
>         if (exynos_drm_check_fimc_device(dev) != 0)
>                 return -ENODEV;
>
> -       ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
> +       num_formats = ARRAY_SIZE(fimc_formats) + ARRAY_SIZE(fimc_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;
>         ctx->dev = dev;
>         ctx->id = of_alias_get_id(dev->of_node, "fimc");
>
> -       /* construct formats/limits array */
> -       num_formats = ARRAY_SIZE(fimc_formats) + ARRAY_SIZE(fimc_tiled_formats);
> -       formats = devm_kcalloc(dev, num_formats, sizeof(*formats),
> -                              GFP_KERNEL);
> -       if (!formats)
> -               return -ENOMEM;
> -
>         /* linear formats */
>         if (ctx->id < 3) {
>                 limits = fimc_4210_limits_v1;
> @@ -1320,9 +1316,6 @@ static int fimc_probe(struct platform_device *pdev)
>                 formats[j].num_limits = num_limits;
>         }
>
> -       ctx->formats = formats;
> -       ctx->num_formats = num_formats;
> -
>         /* resource memory */
>         ctx->regs = devm_platform_ioremap_resource(pdev, 0);
>         if (IS_ERR(ctx->regs))
> --
> 2.56.0
>
>