linux-kernel - Re: [PATCH v2] drm/mediatek: fix uninitialized symbol

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Date:   Fri, 14 Jul 2023 09:27:14 +0000
From:   CK Hu (胡俊光) <ck.hu@...iatek.com>
To:     "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
CC:     "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "clang-built-linux@...glegroups.com" 
        <clang-built-linux@...glegroups.com>,
        Singo Chang (張興國) 
        <Singo.Chang@...iatek.com>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>
Subject: Re: [PATCH v2] drm/mediatek: fix uninitialized symbol

Hi, Nancy:

On Fri, 2023-04-21 at 10:16 +0800, Nancy.Lin wrote:
> fix Smatch static checker warning
>   - uninitialized symbol comp_pdev in mtk_ddp_comp_init.
> 
> Fixes: 0d9eee9118b7 ("drm/mediatek: Add drm ovl_adaptor sub driver
> for MT8195")
> Signed-off-by: Nancy.Lin <nancy.lin@...iatek.com>
> ---
> v2: add Fixes tag
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> index f114da4d36a9..e987ac4481bc 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> @@ -546,7 +546,7 @@ unsigned int
> mtk_drm_find_possible_crtc_by_comp(struct drm_device *drm,
>  int mtk_ddp_comp_init(struct device_node *node, struct mtk_ddp_comp
> *comp,
>  		      unsigned int comp_id)
>  {
> -	struct platform_device *comp_pdev;
> +	struct platform_device *comp_pdev = NULL;
>  	enum mtk_ddp_comp_type type;
>  	struct mtk_ddp_comp_dev *priv;
>  #if IS_REACHABLE(CONFIG_MTK_CMDQ)
> @@ -588,6 +588,9 @@ int mtk_ddp_comp_init(struct device_node *node,
> struct mtk_ddp_comp *comp,
>  	    type == MTK_DSI)
>  		return 0;
>  
> +	if (!comp_pdev)
> +		return -EPROBE_DEFER;

In line 566, the statement is

if (nodo) {
	comp_pdev = ...
}

The comment says that only ovl_adaptoer has no device node, so the
checking should be

if (type != MTK_DISP_OVL_ADAPTOR) {
	comp_pdev = ...
}

and later it would return when type = MTK_DISP_OVL_ADAPTOR,
so there would be no problem of uninitialized symbol.

Regards,
CK

> +
>  	priv = devm_kzalloc(comp->dev, sizeof(*priv), GFP_KERNEL);
>  	if (!priv)
>  		return -ENOMEM;