linux-kernel - Re: [PATCH v7 2/4] driver core: add deferring probe reason to devices

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Date:   Mon, 29 Jun 2020 19:36:42 +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>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Mark Brown <broonie@...nel.org>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Neil Armstrong <narmstrong@...libre.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Daniel Vetter <daniel@...ll.ch>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v7 2/4] driver core: add deferring probe reason to
 devices_deferred property

On Mon, Jun 29, 2020 at 2:22 PM Andrzej Hajda <a.hajda@...sung.com> wrote:
>
> /sys/kernel/debug/devices_deferred property contains list of deferred devices.
> This list does not contain reason why the driver deferred probe, the patch
> improves it.
> The natural place to set the reason is dev_err_probe function introduced recently,
> ie. if dev_err_probe will be called with -EPROBE_DEFER instead of printk the message
> will be attached to deferred device and printed when user read devices_deferred

to a deferred

reads

> property.

...

> @@ -3984,10 +3986,12 @@ int dev_err_probe(const struct device *dev, int err, const char *fmt, ...)
>         vaf.fmt = fmt;
>         vaf.va = &args;
>
> -       if (err != -EPROBE_DEFER)

> +       if (err != -EPROBE_DEFER) {

Why not positive conditional? (Okay, I'm fine with either in this case)

>                 dev_err(dev, "error %d: %pV", err, &vaf);
> -       else
> +       } else {
> +               device_set_deferred_probe_reson(dev, &vaf);
>                 dev_dbg(dev, "error %d: %pV", err, &vaf);
> +       }

To reduce churn, you may move {} addition to the first patch.

...

>         list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe)
> -               seq_printf(s, "%s\n", dev_name(curr->device));
> +               seq_printf(s, "%s\t%s", dev_name(curr->device),
> +                          curr->device->p->deferred_probe_reason ?: "\n");

Hmm... "\t" will be dangling in the latter case.

-- 
With Best Regards,
Andy Shevchenko