Re: [PATCH v7 2/4] drm/mediatek: Fix using wrong drm private data to bind mediatek-drm

Eugen Hristev
2023-07-28T08:49:34Z

Hi,

On 7/27/23 19:41, Jason-JH.Lin wrote:
> Add checking the length of each data path before assigning drm private
> data into all_drm_priv array.
>
> Fixes: 1ef7ed48356c ("drm/mediatek: Modify mediatek-drm for mt8195 multi mmsys support")
> Signed-off-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
> ---
> drivers/gpu/drm/mediatek/mtk_drm_drv.c | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> index 249c9fd6347e..d2fb1fb4e682 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> @@ -351,6 +351,7 @@ static bool mtk_drm_get_all_drm_priv(struct device *dev)
> {
> struct mtk_drm_private *drm_priv = dev_get_drvdata(dev);
> struct mtk_drm_private *all_drm_priv[MAX_CRTC];
> + struct mtk_drm_private *temp_drm_priv;
> struct device_node *phandle = dev->parent->of_node;
> const struct of_device_id *of_id;
> struct device_node *node;
> @@ -373,9 +374,18 @@ static bool mtk_drm_get_all_drm_priv(struct device *dev)
> if (!drm_dev || !dev_get_drvdata(drm_dev))
> continue;
>
> - all_drm_priv[cnt] = dev_get_drvdata(drm_dev);
> - if (all_drm_priv[cnt] && all_drm_priv[cnt]->mtk_drm_bound)
> - cnt++;
> + temp_drm_priv = dev_get_drvdata(drm_dev);
> + if (temp_drm_priv) {
> + if (temp_drm_priv->mtk_drm_bound)
> + cnt++;
> +
> + if (temp_drm_priv->data->main_len)
> + all_drm_priv[0] = temp_drm_priv;
> + else if (temp_drm_priv->data->ext_len)
> + all_drm_priv[1] = temp_drm_priv;
> + else if (temp_drm_priv->data->third_len)
> + all_drm_priv[2] = temp_drm_priv;
> + }

Previously the code was assigning stuff into all_drm_priv[cnt] and
incrementing it.
With your change, it assigns to all_drm_priv[0], [1], [2]. Is this what
you intended ?
If this loop has second run, you will reassign to all_drm_priv again ?
I would expect you to take `cnt` into account.
Also, is it expected that all_drm_priv has holes in the array ?

Eugen

> }
>
> if (drm_priv->data->mmsys_dev_num == cnt) {