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

From: Doug Anderson <dianders@chromium.org>
To: Chen-Yu Tsai <wenst@chromium.org>
Cc: Rob Herring <robh+dt@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	 Matthias Brugger <matthias.bgg@gmail.com>,
	 AngeloGioacchino Del Regno
	<angelogioacchino.delregno@collabora.com>,
	Wolfram Sang <wsa@kernel.org>,
	 Benson Leung <bleung@chromium.org>,
	Tzung-Bi Shih <tzungbi@kernel.org>,
	 chrome-platform@lists.linux.dev, devicetree@vger.kernel.org,
	 linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org,
	 linux-kernel@vger.kernel.org, Johan Hovold <johan@kernel.org>,
	 Hsin-Yi Wang <hsinyi@chromium.org>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	 andriy.shevchenko@linux.intel.com,
	Jiri Kosina <jikos@kernel.org>,
	 linus.walleij@linaro.org, broonie@kernel.org,
	gregkh@linuxfoundation.org,  hdegoede@redhat.com,
	james.clark@arm.com, james@equiv.tech,  keescook@chromium.org,
	rafael@kernel.org, tglx@linutronix.de,
	 Jeff LaBundy <jeff@labundy.com>,
	linux-input@vger.kernel.org, linux-i2c@vger.kernel.org
Subject: Re: [RFC PATCH v3 3/5] platform/chrome: Introduce device tree hardware prober
Date: Fri, 1 Dec 2023 16:58:20 -0800	[thread overview]
Message-ID: <CAD=FV=XV0+G=uFBE_n6WFGVW2szGcKToZgCNTdSrNf3LVk9MOQ@mail.gmail.com> (raw)
In-Reply-To: <20231128084236.157152-4-wenst@chromium.org>

Hi,

On Tue, Nov 28, 2023 at 12:45 AM Chen-Yu Tsai <wenst@chromium.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? ;-)