linux-kernel - Re: [PATCH v13 05/10] drm/bridge: anx7625: Check for Type-C during panel registration

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Message-ID: <CAEXTbpecGhEDrffDobb4NgLw8+vMK2_yVmJw8JGUDruTALm4-w@mail.gmail.com>
Date:   Wed, 8 Mar 2023 18:25:00 +0800
From:   Pin-yen Lin <treapking@...omium.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Prashant Malani <pmalani@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        Xin Ji <xji@...logixsemi.com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Lyude Paul <lyude@...hat.com>, linux-kernel@...r.kernel.org,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        chrome-platform@...ts.linux.dev,
        Nícolas F . R . A . Prado 
        <nfraprado@...labora.com>, Marek Vasut <marex@...x.de>,
        Hsin-Yi Wang <hsinyi@...omium.org>, devicetree@...r.kernel.org,
        Allen Chen <allen.chen@....com.tw>,
        dri-devel@...ts.freedesktop.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Stephen Boyd <swboyd@...omium.org>, linux-acpi@...r.kernel.org,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH v13 05/10] drm/bridge: anx7625: Check for Type-C during
 panel registration

HI Andy,

On Mon, Mar 6, 2023 at 7:52 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Fri, Mar 03, 2023 at 10:33:45PM +0800, Pin-yen Lin wrote:
> > The output port endpoints can be connected to USB-C connectors.
> > Running drm_of_find_panel_or_bridge() with such endpoints leads to
> > a continuous return value of -EPROBE_DEFER, even though there is
> > no panel present.
> >
> > To avoid this, check for the existence of a "mode-switch" property in
> > the port endpoint, and skip panel registration completely if so.
>
> ...
>
> > +     port_node = of_graph_get_port_by_id(np, 1);
> > +     count = typec_mode_switch_node_count(&port_node->fwnode);
>
> Do you need to drop reference count here?
> (I don't know myself, so, please check this)
>
> If no, patch LGTM.

The helper completes the for-loop of fwnode_for_each_child_node, which
drops the reference count whenever the next node is get. So we don't
need drop the reference count here.
>
> > +     if (count)
> > +             return 0;
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
Best regards,
Pin-yen