linux-kernel - Re: Applied "regulator: core: Link consumer with regulator driver" to the regulator tree

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Date:   Mon, 9 Jul 2018 13:26:08 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Benjamin Gaignard <benjamin.gaignard@...aro.org>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        pascal paillet <p.paillet@...com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        rafael.j.wysocki@...el.co
Subject: Re: Applied "regulator: core: Link consumer with regulator driver"
 to the regulator tree

On Mon, Jul 09, 2018 at 02:13:35PM +0200, Benjamin Gaignard wrote:
> 2018-07-09 13:17 GMT+02:00 Marek Szyprowski <m.szyprowski@...sung.com>:

> > ------------[ cut here ]------------
> > WARNING: CPU: 1 PID: 1 at drivers/base/core.c:108
> > device_is_dependent+0xa4/0xb4
> > Modules linked in:
> > CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.18.0-rc3-next-20180706 #112

> > It looks that some more checks have to be done before adding a link between
> > regulator consumer and regulator driver, because it is not that uncommon
> > that
> > regulator consumer shares the parent device with regulator provider.

> Each time device_is_dependent() will return 1 we have a warn_on.
> It is strange since returning 1 is well documented on function description.
> I don't know if we can safely remove the warn_on or if their is a good
> reason to keep it.
> Rafael what do you think about that ?

It's trying to tell you that there's probably a higher level bug if
you're adding a link from a device to itself.  That's not super
unreasonable, though it is going to mean that every bit of generic code
like this adding links is going to have to add checks (or we have to
downgrade or make optional the WARN_ON).

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