linux-kernel - Re: [PATCH v8 3/8] drm/mediatek: Fix using wrong drm private data to bind mediatek-drm

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Date:   Sat, 5 Aug 2023 08:05:51 +0000
From:   Jason-JH Lin (林睿祥) 
        <Jason-JH.Lin@...iatek.com>
To:     "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>,
        "eugen.hristev@...labora.com" <eugen.hristev@...labora.com>
CC:     "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        Singo Chang (張興國) 
        <Singo.Chang@...iatek.com>,
        Johnson Wang (王聖鑫) 
        <Johnson.Wang@...iatek.com>,
        Jason-ch Chen (陳建豪) 
        <Jason-ch.Chen@...iatek.com>,
        Shawn Sung (宋孝謙) 
        <Shawn.Sung@...iatek.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>
Subject: Re: [PATCH v8 3/8] drm/mediatek: Fix using wrong drm private data to
 bind mediatek-drm

Hi Eugen,

Thanks for the reviews.

On Thu, 2023-08-03 at 16:22 +0300, Eugen Hristev wrote:
> On 8/2/23 17:47, Jason-JH.Lin wrote:
> > In mtk_drm_kms_init(), each element in all_drm_priv should has one
> > display path private data only, such as:
> > all_drm_priv[CRTC_MAIN] should has main_path data only
> > all_drm_priv[CRTC_EXT] should has ext_path data only
> > all_drm_priv[CRTC_THIRD] should has third_path data only
> 
> s/should has/should have/ ?
> 

Although each element is singular, `should have` is correct.

`should` is an auxiliary verb, so we can only use infinitive verbs
after that. 

So this part of comment should be like this:
In mtk_drm_kms_init(), each element in all_drm_priv should have one
display path private data, such as:
all_drm_priv[CRTC_MAIN] should only have main_path data
all_drm_priv[CRTC_EXT] should only have ext_path data
all_drm_priv[CRTC_THIRD] should only have third_path data

Right?

> > 
> > So we need to add the length checking for each display path before
> > assigning their 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>
> > Reviewed-by: AngeloGioacchino Del Regno <
> > angelogioacchino.delregno@...labora.com>
> > Reviewed-by: CK Hu <ck.hu@...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 89a38561ba27..c12886f31e54 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) {
> 
> This is inside a 'for' loop right ?
> Why don't you just 'continue' if temp_drm_priv is null ?
> 

Yes, you are right.
I'll use `if (!temp_drm_priv) continue;` to make this statement
simpler. Thanks.

Regards,
Jason-JH.Lin.

> 
> > +			if (temp_drm_priv->mtk_drm_bound)
> > +				cnt++;
> > +
> > +			if (temp_drm_priv->data->main_len)
> > +				all_drm_priv[CRTC_MAIN] =
> > temp_drm_priv;
> > +			else if (temp_drm_priv->data->ext_len)
> > +				all_drm_priv[CRTC_EXT] = temp_drm_priv;
> > +			else if (temp_drm_priv->data->third_len)
> > +				all_drm_priv[CRTC_THIRD] =
> > temp_drm_priv;
> > +		}
> >   	}
> >   
> >   	if (drm_priv->data->mmsys_dev_num == cnt) {
> 
>