linux-kernel - Re: [PATCH 1/3] driver core: add probe

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Date:   Tue, 16 Oct 2018 16:55:00 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Andrzej Hajda <a.hajda@...sung.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Javier Martinez Canillas <javierm@...hat.com>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH 1/3] driver core: add probe_err log helper

On Tue, Oct 16, 2018 at 3:55 PM Andrzej Hajda <a.hajda@...sung.com> wrote:
> On 16.10.2018 13:29, Andrzej Hajda wrote:
> > On 16.10.2018 13:01, Andy Shevchenko wrote:
> >> On Tue, Oct 16, 2018 at 10:22 AM Andrzej Hajda <a.hajda@...sung.com> wrote:
> >>> During probe every time driver gets resource it should usually check for error
> >>> printk some message if it is not -EPROBE_DEFER and return the error. This
> >>> pattern is simple but requires adding few lines after any resource acquisition
> >>> code, as a result it is often omited or implemented only partially.
> >>> probe_err helps to replace such code seqences with simple call, so code:
> >>>         if (err != -EPROBE_DEFER)
> >>>                 dev_err(dev, ...);
> >>>         return err;
> >>> becomes:
> >>>         return probe_err(dev, err, ...);

> >>> +               va_start(args, fmt);
> >>> +
> >>> +               vaf.fmt = fmt;
> >>> +               vaf.va = &args;
> >>> +
> >>> +               __dev_printk(KERN_ERR, dev, &vaf);

> >> It would be nice to print an error code as well, wouldn't it?
> > Hmm, on probe fail error is printed anyway (with exception of
> > EPROBE_DEFER, ENODEV and ENXIO):
> >     "probe of %s failed with error %d\n"
> > On the other side currently some drivers prints the error code anyway
> > via dev_err or similar, so I guess during conversion to probe_err it
> > should be removed then.
> >
> > If we add error code to probe_err is it OK to report it this way?
> >     dev_err(dev, "%V, %d\n", &vaf, err);
>
> Ups, I forgot that message passed to probe_err will contain already
> newline character.

You may consider not to pass it.

> So the err must be before message passed to probe_err, for example:
>     dev_err(dev, "err=%d: %V\n", err, &vaf);

> Is it OK?

For me would work either (no \n in the message, or err preceding the message).

-- 
With Best Regards,
Andy Shevchenko