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References: <20230905084922.3908121-1-mwalle@kernel.org>
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From:   Chun-Kuang Hu <chunkuang.hu@kernel.org>
Date:   Fri, 8 Dec 2023 07:54:00 +0800
Message-ID: <CAAOTY_9xrt_ku-fZotJAnPa2ns-2PCGken4TepMrQYG9KEJcFA@mail.gmail.com>
Subject: Re: [PATCH v4 1/2] drm/mediatek: fix kernel oops if no crtc is found
To:     Michael Walle <mwalle@kernel.org>
Cc:     =?UTF-8?B?TsOtY29sYXMgRiAuIFIgLiBBIC4gUHJhZG8=?= 
        <nfraprado@collabora.com>, Chun-Kuang Hu <chunkuang.hu@kernel.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        "Nancy . Lin" <nancy.lin@mediatek.com>,
        Frank Wunderlich <frank-w@public-files.de>,
        Jitao Shi <jitao.shi@mediatek.com>,
        Stu Hsieh <stu.hsieh@mediatek.com>,
        dri-devel@lists.freedesktop.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
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Hi, Michael:

Michael Walle <mwalle@kernel.org> =E6=96=BC 2023=E5=B9=B49=E6=9C=885=E6=97=
=A5 =E9=80=B1=E4=BA=8C =E4=B8=8B=E5=8D=884:49=E5=AF=AB=E9=81=93=EF=BC=9A
>
> drm_crtc_from_index(0) might return NULL if there are no CRTCs
> registered at all which will lead to a kernel oops in
> mtk_drm_crtc_dma_dev_get(). Add the missing return value check.

Applied to mediatek-drm-fixes [1], thanks.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/=
log/?h=3Dmediatek-drm-fixes

Regards,
Chun-Kuang.

>
> Fixes: 0d9eee9118b7 ("drm/mediatek: Add drm ovl_adaptor sub driver for MT=
8195")
> Signed-off-by: Michael Walle <mwalle@kernel.org>
> Reviewed-by: N=C3=ADcolas F. R. A. Prado <nfraprado@collabora.com>
> Tested-by: N=C3=ADcolas F. R. A. Prado <nfraprado@collabora.com>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collab=
ora.com>
> ---
> v4:
>  - collected tags
> v3:
>  - none
> v2:
>  - collected tags
>  - fixed typos
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_drv.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/med=
iatek/mtk_drm_drv.c
> index 93552d76b6e7..2c582498817e 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> @@ -420,6 +420,7 @@ static int mtk_drm_kms_init(struct drm_device *drm)
>         struct mtk_drm_private *private =3D drm->dev_private;
>         struct mtk_drm_private *priv_n;
>         struct device *dma_dev =3D NULL;
> +       struct drm_crtc *crtc;
>         int ret, i, j;
>
>         if (drm_firmware_drivers_only())
> @@ -494,7 +495,9 @@ static int mtk_drm_kms_init(struct drm_device *drm)
>         }
>
>         /* Use OVL device for all DMA memory allocations */
> -       dma_dev =3D mtk_drm_crtc_dma_dev_get(drm_crtc_from_index(drm, 0))=
;
> +       crtc =3D drm_crtc_from_index(drm, 0);
> +       if (crtc)
> +               dma_dev =3D mtk_drm_crtc_dma_dev_get(crtc);
>         if (!dma_dev) {
>                 ret =3D -ENODEV;
>                 dev_err(drm->dev, "Need at least one OVL device\n");
> --
> 2.39.2
>