linux-kernel - Re: [PATCH v13 03/10] drm/display: Add Type-C switch helpers

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Message-ID: <CAEXTbpf4zM+70BCef6rdfz35TQnQ+ozaXAvOaEZVnqqe6MDOOg@mail.gmail.com>
Date:   Wed, 8 Mar 2023 18:20:14 +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,
        Alex Deucher <alexander.deucher@....com>,
        Douglas Anderson <dianders@...omium.org>,
        Imre Deak <imre.deak@...el.com>,
        Jani Nikula <jani.nikula@...el.com>,
        Ville Syrjälä <ville.syrjala@...ux.intel.com>
Subject: Re: [PATCH v13 03/10] drm/display: Add Type-C switch helpers

Hi Andy,

Thanks for the review.

On Mon, Mar 6, 2023 at 7:49 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Fri, Mar 03, 2023 at 10:33:43PM +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 "reg" 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;
> > +     }
> > +
> > +     return 0;
>
> Can be simply
>
>         port_data->typec_mux = typec_mux_register(dev, &mux_desc);
>         ret = PTR_ERR_OR_ZERO(port_data->typec_mux);
>         if (ret)
>                 dev_err(dev, "Mode switch register for port %d failed: %d\n",
>                         port_num, ret);
>
>         return ret;
>
This was suggested by Angelo in [1], but you are not the first
reviewer that finds this weird... I'll update this in the next
version.

[1]: https://lore.kernel.org/all/023519eb-0adb-3b08-71b9-afb92a6cceaf@collabora.com/

> ...
>
> > +     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;
>
> How often this function _can_ be called during the runtime?
> If it's _possible_ to call it infinite times, consider *not* using devm.

I would expect this function to be only called during driver probing,
and this is the case for the current users in this series. So I think
this is only called once if EPROBDE_DEFER doesn't count.
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
Best regards,
Pin-yen