linux-kernel - Re: [PATCH v6 11/12] platform/chrome: Introduce device tree hardware prober

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Message-ID: <CAGXv+5GpKu-b4_dbRcuSG4NxQi_FKh9p7iMh6DfgavkLFdLLdQ@mail.gmail.com>
Date: Thu, 5 Sep 2024 11:52:32 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
To: Tzung-Bi Shih <tzungbi@...nel.org>
Cc: Rob Herring <robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>, 
	Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Wolfram Sang <wsa@...nel.org>, 
	Benson Leung <bleung@...omium.org>, Mark Brown <broonie@...nel.org>, 
	Liam Girdwood <lgirdwood@...il.com>, 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, 
	Douglas Anderson <dianders@...omium.org>, Johan Hovold <johan@...nel.org>, Jiri Kosina <jikos@...nel.org>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, linux-i2c@...r.kernel.org
Subject: Re: [PATCH v6 11/12] platform/chrome: Introduce device tree hardware prober

On Wed, Sep 4, 2024 at 6:08 PM Tzung-Bi Shih <tzungbi@...nel.org> wrote:
>
> On Wed, Sep 04, 2024 at 05:00:13PM +0800, Chen-Yu Tsai wrote:
> > diff --git a/drivers/platform/chrome/chromeos_of_hw_prober.c b/drivers/platform/chrome/chromeos_of_hw_prober.c
> [...]
> > +static int chromeos_of_hw_prober_probe(struct platform_device *pdev)
> > +{
> > +     for (size_t i = 0; i < ARRAY_SIZE(hw_prober_platforms); i++) {
> > +             int ret;
> > +
> > +             if (!of_machine_is_compatible(hw_prober_platforms[i].compatible))
> > +                     continue;
> > +
> > +             ret = hw_prober_platforms[i].prober(&pdev->dev, hw_prober_platforms[i].data);
> > +             /* Ignore unrecoverable errors and keep going through other probers */
> > +             if (ret == -EPROBE_DEFER)
> > +                     return ret;
>
> Is it harmless if some of the components get probed multiple times?  E.g.:
> comp1 probed -> comp2 probed -> comp3 returned -EPROBE_DEFER -> some time
> later, chromeos_of_hw_prober_probe() gets called again.

Yes it is harmless. Components already enabled will not get disabled
in the error path. And the prober that enabled that component will see
that a component was enabled, and skip doing the whole process again.

So something like:

    comp1 probed -> comp2 probed -> comp3 -EPROBE_DEFER ->
        comp1 skip -> comp2 skip -> comp3 probed


ChenYu