linux-kernel - Re: [PATCH] usb: dwc3: drd: Avoid error when extcon is missing

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Date:   Fri, 11 Dec 2020 23:14:21 +0200
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        John Stultz <john.stultz@...aro.org>
Subject: Re: [PATCH] usb: dwc3: drd: Avoid error when extcon is missing

On Fri, 11 Dec 2020 at 16:48, Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Fri, Dec 11, 2020 at 04:24:21PM +0200, Sam Protsenko wrote:
> > If "port" node is missing in PHY controller node, dwc3_get_extcon()
> > isn't able to find extcon device. This is perfectly fine in case when
> > "usb-role-switch" or OTG is used, but next misleading error message is
> > printed in that case, from of_graph_get_remote_node():
> >
> >     OF: graph: no port node found in /phy@...4abcd
> >
> > Avoid printing that message by checking if port node exists in PHY node
> > before calling of_graph_get_remote_node().
>
> So, this has to be v2...
> Anyway, see below.
>
> ...
>
> >  static struct extcon_dev *dwc3_get_extcon(struct dwc3 *dwc)
> >  {
> >       struct device *dev = dwc->dev;
> > -     struct device_node *np_phy, *np_conn;
> > -     struct extcon_dev *edev;
> > +     struct device_node *np_phy;
> > +     struct extcon_dev *edev = NULL;
> >       const char *name;
> >
> >       if (device_property_read_bool(dev, "extcon"))
> > @@ -462,15 +462,22 @@ static struct extcon_dev *dwc3_get_extcon(struct dwc3 *dwc)
> >               return edev;
> >       }
> >
> > +     /*
> > +      * Try to get extcon device from USB PHY controller's "port" node.
> > +      * Check if it has the "port" node first, to avoid printing the error
> > +      * message from underlying code, as it's a valid case: extcon device
> > +      * (and "port" node) may be missing in case of "usb-role-switch" or OTG
> > +      * mode.
> > +      */
> >       np_phy = of_parse_phandle(dev->of_node, "phys", 0);
> > -     np_conn = of_graph_get_remote_node(np_phy, -1, -1);
> > +     if (of_graph_is_present(np_phy)) {
> > +             struct device_node *np_conn;
> >
> > -     if (np_conn)
> > -             edev = extcon_find_edev_by_node(np_conn);
> > -     else
> > -             edev = NULL;
> > -
> > -     of_node_put(np_conn);
> > +             np_conn = of_graph_get_remote_node(np_phy, -1, -1);
> > +             if (np_conn)
> > +                     edev = extcon_find_edev_by_node(np_conn);
> > +             of_node_put(np_conn);
> > +     }
> >       of_node_put(np_phy);
> >
> >       return edev;
>
>
> Why not do it slightly different, i.e.
>
> -       np_conn = of_graph_get_remote_node(np_phy, -1, -1);
> +       if (of_graph_is_present(np_phy))
> +               np_conn = of_graph_get_remote_node(np_phy, -1, -1);
> +       else
> +               np_conn = NULL;
>
> ?
>

Thanks for the review, Andy! I'll address this in v3.

> --
> With Best Regards,
> Andy Shevchenko
>
>