linux-kernel - Re: [RFC PATCH v3 3/5] platform/chrome: Introduce device tree hardware prober

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Message-ID: <CAD=FV=XV0+G=uFBE_n6WFGVW2szGcKToZgCNTdSrNf3LVk9MOQ@mail.gmail.com>
Date:   Fri, 1 Dec 2023 16:58:20 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Chen-Yu Tsai <wenst@...omium.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Wolfram Sang <wsa@...nel.org>,
        Benson Leung <bleung@...omium.org>,
        Tzung-Bi Shih <tzungbi@...nel.org>,
        chrome-platform@...ts.linux.dev, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Johan Hovold <johan@...nel.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        andriy.shevchenko@...ux.intel.com, Jiri Kosina <jikos@...nel.org>,
        linus.walleij@...aro.org, broonie@...nel.org,
        gregkh@...uxfoundation.org, hdegoede@...hat.com,
        james.clark@....com, james@...iv.tech, keescook@...omium.org,
        rafael@...nel.org, tglx@...utronix.de,
        Jeff LaBundy <jeff@...undy.com>, linux-input@...r.kernel.org,
        linux-i2c@...r.kernel.org
Subject: Re: [RFC PATCH v3 3/5] platform/chrome: Introduce device tree
 hardware prober

Hi,

On Tue, Nov 28, 2023 at 12:45 AM Chen-Yu Tsai <wenst@...omium.org> wrote:
>
> @@ -61,6 +61,17 @@ config CHROMEOS_TBMC
>           To compile this driver as a module, choose M here: the
>           module will be called chromeos_tbmc.
>
> +config CHROMEOS_OF_HW_PROBER
> +       bool "ChromeOS Device Tree Hardware Prober"

Any reason that it can't be a module?


> +       depends on OF
> +       depends on I2C
> +       select OF_DYNAMIC
> +       default OF

You probably don't want "default OF". This means that everyone will
automatically get this new driver enabled which is unlikely to be
right.


> +static int chromeos_of_hw_prober_probe(struct platform_device *pdev)
> +{
> +       for (size_t i = 0; i < ARRAY_SIZE(hw_prober_platforms); i++)
> +               if (of_machine_is_compatible(hw_prober_platforms[i].compatible)) {
> +                       int ret;
> +
> +                       ret = hw_prober_platforms[i].prober(&pdev->dev,
> +                                                           hw_prober_platforms[i].data);
> +                       if (ret)

Should it only check for -EPROBE_DEFER here? ...and then maybe warn
for other cases and go through the loop? If there's some error
enabling the touchscreen I'd still want the trackpad to probe...


> +                               return ret;
> +               }
> +
> +       return 0;

Random thought: once we get here, the driver is useless / just wasting
memory. Any way to have it freed? ;-)