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Date: Thu, 12 Jan 2017 18:41:42 +0100
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Rob Herring <robh@kernel.org>
Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Mark Brown <broonie@kernel.org>,
        Tomeu Vizoso <tomeu.vizoso@collabora.com>,
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Thierry Reding <thierry.reding@gmail.com>
Subject: Re: sysfs deferred_probe attribute
Message-ID: <20170112174142.GA23954@kroah.com>
References: <CAL_JsqLSfv4sbb9NRCTUOGu9vwEtE4buWUpcP58tZSxggcy08Q@mail.gmail.com>
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On Thu, Jan 12, 2017 at 11:27:01AM -0600, Rob Herring wrote:
> I just noticed that we have a new device attribute 'deferred_probe'
> added in 4.10 with this commit:
> 
> commit 6751667a29d6fd64afb9ce30567ad616b68ed789
> Author: Ben Hutchings <ben.hutchings@codethink.co.uk>
> Date:   Tue Aug 16 14:34:18 2016 +0100
> 
>     driver core: Add deferred_probe attribute to devices in sysfs
> 
>     It is sometimes useful to know that a device is on the deferred probe
>     list rather than, say, not having a driver available.  Expose this
>     information to user-space.
> 
>     Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
>     Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> 
> It seems like a bad idea to add an ABI for an internal kernel feature.
> When/if we replace deferred probe with something better based on
> functional dependencies are we going to keep this attr around? Or
> remove it and assume no userspace uses it? Perhaps it should be hidden
> behind CONFIG_DEBUG or just make a debugfs file that lists the
> deferred list. Then you wouldn't have to hunt for what got deferred.

Ah, debugfs would be nice, I'd much prefer that.  I don't know how Ben
is using this, but I think that would make more sense to me.

thanks,

greg k-h