[PATCH v4 1/2] drm/mediatek: fix kernel oops if no crtc is found

[Chun-Kuang Hu]

Hi, Michael:

Michael Walle <mwalle at kernel.org> 於 2023年9月5日 週二 下午4:49寫道：
>
> 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=mediatek-drm-fixes

Regards,
Chun-Kuang.

>
> Fixes: 0d9eee9118b7 ("drm/mediatek: Add drm ovl_adaptor sub driver for MT8195")
> Signed-off-by: Michael Walle <mwalle at kernel.org>
> Reviewed-by: Nícolas F. R. A. Prado <nfraprado at collabora.com>
> Tested-by: Nícolas F. R. A. Prado <nfraprado at collabora.com>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.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/mediatek/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 = drm->dev_private;
>         struct mtk_drm_private *priv_n;
>         struct device *dma_dev = 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 = mtk_drm_crtc_dma_dev_get(drm_crtc_from_index(drm, 0));
> +       crtc = drm_crtc_from_index(drm, 0);
> +       if (crtc)
> +               dma_dev = mtk_drm_crtc_dma_dev_get(crtc);
>         if (!dma_dev) {
>                 ret = -ENODEV;
>                 dev_err(drm->dev, "Need at least one OVL device\n");
> --
> 2.39.2
>