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

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Message-ID: <d74f959b-2255-4587-e99c-2c6b043dc44c@collabora.com>
Date:   Fri, 28 Jul 2023 11:47:49 +0300
From:   Eugen Hristev <eugen.hristev@...labora.com>
To:     "Jason-JH.Lin" <jason-jh.lin@...iatek.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     Matthias Brugger <matthias.bgg@...il.com>,
        Jason-ch Chen <jason-ch.chen@...iatek.com>,
        Johnson Wang <johnson.wang@...iatek.com>,
        Singo Chang <singo.chang@...iatek.com>,
        Nancy Lin <nancy.lin@...iatek.com>,
        Shawn Sung <shawn.sung@...iatek.com>,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v7 2/4] drm/mediatek: Fix using wrong drm private data to
 bind mediatek-drm

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@...iatek.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) {