linux-kernel - Re: [PATCH v9 0/4] driver core: add probe error check helper

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Date:   Thu, 30 Jul 2020 10:46:31 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Jonas Karlman <jonas@...boo.se>,
        lkml <linux-kernel@...r.kernel.org>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Neil Armstrong <narmstrong@...libre.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH v9 0/4] driver core: add probe error check helper

On Thu, Jul 30, 2020 at 9:49 AM Mark Brown <broonie@...nel.org> wrote:
>
> On Thu, Jul 30, 2020 at 09:18:30AM -0700, Dmitry Torokhov wrote:
>
> > I believe it still has not been answered why this can't be pushed into
> > resource providers (clock, regulators, gpio, interrupts, etc),
> > especially for devm APIs where we know exactly what device we are
> > requesting a resource for, so that individual drivers do not need to
> > change anything.
>
> The error messages are frequently in the caller rather than the
> frameworks, it's often helpful for the comprehensibility of the error
> messages especially in cases where things may be legitimately absent.

Not for deferral. All you need to know in this case is:

"device A is attempting to request resource B which is not ready yet"

There is nothing to handle on the caller part except to float the error up.

>
> >                  We can mark the device as being probed so that probe
> > deferral is only handled when we actually execute probe() (and for the
> > bonus points scream loudly if someone tries to return -EPROBE_DEFER
> > outside of probe path).
>
> Is this a big issue?

We do not know ;) Probably not. It will just get reported as an
ordinary failure and the driver will handle it somehow. Still it would
be nice to know if we attempt to raise deferrals in code paths where
they do not make sense.

Thanks.

-- 
Dmitry