linux-kernel - Re: [PATCH v3] driver core: Break infinite loop when deferred probe can't be satisfied

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Date:   Mon, 8 Jun 2020 15:11:07 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Marco Felsch <m.felsch@...gutronix.de>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Grant Likely <grant.likely@....com>,
        Saravana Kannan <saravanak@...gle.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        artem.bityutskiy@...ux.intel.com, Felipe Balbi <balbi@...nel.org>,
        Mark Brown <broonie@...nel.org>, Ferry Toth <fntoth@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        "Rafael J. Wysocki" <rafael@...nel.org>, kernel-team@...roid.com,
        nd <nd@....com>, Sascha Hauer <kernel@...gutronix.de>
Subject: Re: [PATCH v3] driver core: Break infinite loop when deferred probe
 can't be satisfied

On Mon, Jun 8, 2020 at 2:59 PM Marco Felsch <m.felsch@...gutronix.de> wrote:
> On 20-06-08 14:13, Andy Shevchenko wrote:
> > On Mon, Jun 8, 2020 at 12:20 PM Marco Felsch <m.felsch@...gutronix.de> wrote:
> > > On 20-03-26 18:31, Andy Shevchenko wrote:

> > > sorry for picking this up again but I stumbled above the same issue
> > > within the driver imx/drm driver which is using the component framework.
> > > I end up in a infinity boot loop if I enabled the HDMI (which is the
> > > DesignWare bridge device) and the LVDS support and the LVDS bind return
> > > with EPROBE_DEFER. There are no words within the component framework docs
> > > which says that this is forbidden. Of course we can work-around the
> > > driver-core framework but IMHO this shouldn't be the way to go. I do not
> > > say that we should revert the commit introducing the regression but we
> > > should address this not only by extending the docs since the most
> > > drm-drivers are using the component framework and can end up in the same
> > > situation.
> > >
> > > > > It can be solved by refactoring the driver probe routine. If a resource is
> > > > > required to be present, then check that it is available early; before
> > > > > registering child devices.
> > > >
> > > > We fix one and leave others.
> > >
> > > E.g. the imx-drm and the sunxi driver...
> >
> > Just out of curiosity, does my patch fix an issue for you?
>
> I didn't applied your patch yet. I can test it if you want.

If you can, thanks!

> > > > > The proposed solution to modify driver core is fragile and susceptible to
> > > > > side effects from other probe paths. I don't think it is the right approach.

-- 
With Best Regards,
Andy Shevchenko