linux-kernel - Re: Re: [PATCH] media: vsp1: Fix runtime PM imbalance in vsp1

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Date:   Mon, 8 Jun 2020 11:03:26 +0800 (GMT+08:00)
From:   dinghao.liu@....edu.cn
To:     "Laurent Pinchart" <laurent.pinchart@...asonboard.com>
Cc:     kjlu@....edu,
        "Kieran Bingham" <kieran.bingham+renesas@...asonboard.com>,
        "Mauro Carvalho Chehab" <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH] media: vsp1: Fix runtime PM imbalance in vsp1_probe

Hi Laurent,

> > 
> > I wonder how many bugs we have today, and how many bugs will keep
> > appearing in the future, due to this historical design mistake :-( 
> > 

Good question. It's hard to say if this is a design mistake (some use
of this API does not check its return value and expects it always to
increment the usage counter). But it does make developers misuse it easier.

> > 
> > This change looks good to me, but we also need a similar change in the
> > vsp1_device_get() function if I'm not mistaken. Could you combine both
> > in the same patch ?
> 

Thank you for your advice! I think you are right and I will fix this in the
next version of patch. 

> And actually, after fixing vsp1_device_get(), we should replace the
> pm_runtime_get_sync() call here with vsp1_device_get(), and the
> pm_runtime_put_sync() below with vsp1_device_put(), so there would be no
> need to call pm_runtime_put_sync() manually in the error path here.
> 

The parameter type of vsp1_device_get() and vsp1_device_put() is "struct 
vsp1_device". If we want to use these two wrappers, we need to adjust their 
parameter type to "struct platform_device" or "struct device", which may 
lead to errors in other callers. Maybe we should leave it as it is.

Regards,
Dinghao