linux-kernel - Re: [PATCH] driver core: add a debugfs entry to show deferred devices

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Message-ID: <CAHp75VcOd5K+T6bkxyz3qgqNr4-=K9GGRh+DQ_qgW7dGKdzO5A@mail.gmail.com>
Date:   Wed, 20 Jun 2018 02:43:14 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Javier Martinez Canillas <javierm@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Mark Brown <broonie@...nel.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH] driver core: add a debugfs entry to show deferred devices

On Wed, Jun 20, 2018 at 1:51 AM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> On Tue, Jun 19, 2018 at 10:59:14PM +0200, Javier Martinez Canillas wrote:
>> For debugging purposes it may be useful to know what are the devices whose
>> probe function was deferred. Add a debugfs entry showing that information.
>>
>>   $ cat /sys/kernel/debug/deferred_devices
>>   48070000.i2c:twl@48:bci
>>   musb-hdrc.0.auto
>>   omapdrm.0


> And what is the use of this file?  What can you do with this
> information?  Who is going to use it?  Don't we have other deferred
> probe debugging somewhere else?

Indeed.

Javier, have you tried to add 'initcall_debug' to a kernel command
line followed by 'dyndbg="file drivers/base/dd.c +p"'?

-- 
With Best Regards,
Andy Shevchenko