linux-kernel - Re: [PATCH 1/3] drm: rcar-du: add missing of_node

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Date:   Mon, 14 Jan 2019 17:19:47 +0100 (CET)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        kernel-janitors@...r.kernel.org, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] drm: rcar-du: add missing of_node_put



On Mon, 14 Jan 2019, Kieran Bingham wrote:

> Hi Julia,
>
> Thank you for the patch,
>
> On 13/01/2019 09:44, Julia Lawall wrote:
> > Add an of_node_put when the result of of_graph_get_remote_port_parent is
> > not available.
> >
> > The semantic match that finds this problem is as follows
> > (http://coccinelle.lip6.fr):
> >
> > // <smpl>
> > @r exists@
> > local idexpression e;
> > expression x;
> > @@
> > e = of_graph_get_remote_port_parent(...);
> > ... when != x = e
> >     when != true e == NULL
> >     when != of_node_put(e)
> >     when != of_fwnode_handle(e)
> > (
> > return e;
> > |
> > *return ...;
> > )
> > // </smpl>
> >
>
> For this part at least:
>
> Reviewed-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
>
> But a little discussion below:
>
>
> > Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>
>
> This does indeed look like a missing of_node_put() but I don't think it
> will be the only one in that code. It gets a bit tangled - and I think
> there's possibly another missing put on the error path of
>
>         if (!encoder) {
>                 dev_warn(rcdu->dev,
>                          "no encoder found for endpoint %pOF, skipping\n",
>                          ep->local_node);
>                 return -ENODEV;
>         }
>
> because that implies that no encoder was found, and thus -
>                 encoder = entity;
>
> was not executed, and the tail of that function calls:
>
>          of_node_put(encoder);
>
> which would have been the final of_node_put(entity)

Looking at it again, I agree.  I can just extend this patch.

julia


>
>
> I think that part could be considered separate to this patch, but it's
> also quite closely related. Either way - I think it needs a second pair
> of eyes to see if I'm not crazy :)
>
> Regards
>
> Kieran
>
> >
> > ---
> >  drivers/gpu/drm/rcar-du/rcar_du_kms.c |    1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> > index 9c7007d..bc3fcb3 100644
> > --- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> > +++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> > @@ -331,6 +331,7 @@ static int rcar_du_encoders_init_one(struct rcar_du_device *rcdu,
> >  		dev_dbg(rcdu->dev,
> >  			"connected entity %pOF is disabled, skipping\n",
> >  			entity);
> > +		of_node_put(entity);
> >  		return -ENODEV;
> >  	}
> >
> >
>
>