linux-kernel - Re: [PATCH v2 2/2] drm/bridge: parade-ps8640: Populate devices on aux-bus

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Date:   Tue, 26 Oct 2021 12:02:46 -0700
From:   Philip Chen <philipchen@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, dianders@...omium.org,
        Andrzej Hajda <a.hajda@...sung.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jonas Karlman <jonas@...boo.se>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2 2/2] drm/bridge: parade-ps8640: Populate devices on aux-bus

Hi,

On Mon, Oct 25, 2021 at 1:10 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Philip Chen (2021-10-21 14:06:00)
> > diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
> > index 220ca3b03d24..f99a2e0808b7 100644
> > --- a/drivers/gpu/drm/bridge/parade-ps8640.c
> > +++ b/drivers/gpu/drm/bridge/parade-ps8640.c
> > @@ -149,6 +150,23 @@ static inline struct ps8640 *aux_to_ps8640(struct drm_dp_aux *aux)
> >         return container_of(aux, struct ps8640, aux);
> >  }
> >
> > +static bool ps8640_of_panel_on_aux_bus(struct device *dev)
> > +{
> > +       struct device_node *bus, *panel;
> > +
> > +       bus = of_get_child_by_name(dev->of_node, "aux-bus");
> > +       if (!bus)
> > +               return false;
> > +       of_node_put(bus);
>
> This should come after the next line...
>
> > +
> > +       panel = of_get_child_by_name(bus, "panel");
>
> here, so that 'bus' can't go away before getting children nodes. It
> doesn't actually matter in this case because 'device' holds the aux-bus,
> but we shouldn't add anti-patterns to the code lest someone copies it
> where it actually matters.
Thanks for pointing it out.
I will fix it in v3.

>
> > +       if (!panel)
> > +               return false;
> > +       of_node_put(panel);
> > +
> > +       return true;
> > +}
> > +
> >  static void ps8640_ensure_hpd(struct ps8640 *ps_bridge)
> >  {
> >         struct regmap *map = ps_bridge->regmap[PAGE2_TOP_CNTL];
>
> Otherwise
>
> Reviewed-by: Stephen Boyd <swboyd@...omium.org>