linux-kernel - Re: [PATCH v7 3/9] drm/display: Add Type-C switch helpers

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Date:   Sat, 7 Jan 2023 17:16:35 +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 <robert.foss@...aro.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>,
        Nícolas F . R . A . Prado 
        <nfraprado@...labora.com>, Xin Ji <xji@...logixsemi.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        linux-kernel@...r.kernel.org, Allen Chen <allen.chen@....com.tw>,
        linux-acpi@...r.kernel.org, Lyude Paul <lyude@...hat.com>,
        dri-devel@...ts.freedesktop.org, chrome-platform@...ts.linux.dev,
        Javier Martinez Canillas <javierm@...hat.com>,
        Marek Vasut <marex@...x.de>, devicetree@...r.kernel.org,
        Stephen Boyd <swboyd@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Imre Deak <imre.deak@...el.com>,
        Jani Nikula <jani.nikula@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Khaled Almahallawy <khaled.almahallawy@...el.com>,
        Ville Syrjälä <ville.syrjala@...ux.intel.com>,
        shaomin Deng <dengshaomin@...rlc.com>
Subject: Re: [PATCH v7 3/9] drm/display: Add Type-C switch helpers

Hi Andy,

Thanks for the review.

On Thu, Jan 5, 2023 at 11:41 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Thu, Jan 05, 2023 at 09:24:51PM +0800, Pin-yen Lin wrote:
> > Add helpers to register and unregister Type-C "switches" for bridges
> > capable of switching their output between two downstream devices.
> >
> > The helper registers USB Type-C mode switches when the "mode-switch"
> > and the "data-lanes" properties are available in Device Tree.
>
> ...
>
> > +     port_data->typec_mux = typec_mux_register(dev, &mux_desc);
> > +     if (IS_ERR(port_data->typec_mux)) {
> > +             ret = PTR_ERR(port_data->typec_mux);
> > +             dev_err(dev, "Mode switch register for port %d failed: %d\n",
> > +                     port_num, ret);
> > +     }
> > +
> > +     return ret;
>
> ...
>
> > +     struct device_node *sw;
>
> > +     int ret = 0;
>
> It's easy to break things if you squeeze more code in the future in this
> function, so I recommend to split assignment to be closer to its first user
> (see below).
>
> > +     for_each_child_of_node(port, sw) {
> > +             if (of_property_read_bool(sw, "mode-switch"))
> > +                     switch_desc->num_typec_switches++;
> > +     }
> > +
> > +     if (!switch_desc->num_typec_switches) {
> > +             dev_warn(dev, "No Type-C switches node found\n");
>
> > +             return ret;
>
> return 0;

Thanks for the suggestion. I'll update this in v8.
>
> > +     }
> > +
> > +     switch_desc->typec_ports = devm_kcalloc(
> > +             dev, switch_desc->num_typec_switches,
> > +             sizeof(struct drm_dp_typec_port_data), GFP_KERNEL);
> > +
> > +     if (!switch_desc->typec_ports)
> > +             return -ENOMEM;
>
> > +     /* Register switches for each connector. */
> > +     for_each_child_of_node(port, sw) {
> > +             if (!of_property_read_bool(sw, "mode-switch"))
> > +                     continue;
> > +             ret = drm_dp_register_mode_switch(dev, sw, switch_desc, data, mux_set);
> > +             if (ret) {
> > +                     dev_err(dev, "Failed to register mode switch: %d\n", ret);
> > +                     of_node_put(sw);
> > +                     break;
> > +             }
> > +     }
>
> > +     if (ret)
> > +             drm_dp_unregister_typec_switches(switch_desc);
> > +
> > +     return ret;
>
> Why not adding a goto label?

I didn't know that goto label is preferred even when there are no
duplicated code blocks in the function.

I'll update this accordingly in v8.
>
>                 ret = drm_dp_register_mode_switch(dev, sw, switch_desc, data, mux_set);
>                 if (ret)
>                         goto err_unregister_typec_switches;
>
>         return 0;
>
> err_unregister_typec_switches:
>         of_node_put(sw);
>         drm_dp_unregister_typec_switches(switch_desc);
>         dev_err(dev, "Failed to register mode switch: %d\n", ret);
>         return ret;
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
Best regards,
Pin-yen