From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Luis R. Rodriguez" <mcgrof@suse.com>
Subject: Re: [PATCH 1/3] driver core: enable drivers to use deferred probe
	from init
Date: Mon, 28 Jul 2014 18:52:48 +0200
Message-ID: <20140728165248.GE21930@wotan.suse.de>
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To: Yuval Mintz <Yuval.Mintz@qlogic.com>
Cc: "Luis R. Rodriguez" <mcgrof@do-not-panic.com>, "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>, linux-kernel <linux-kernel@vger.kernel.org>, Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>, Joseph Salisbury <joseph.salisbury@canonical.com>, Kay Sievers <kay@vrfy.org>, One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>, Tim Gardner <tim.gardner@canonical.com>, Pierre Fersing <pierre-fersing@pierref.org>, Andrew Morton <akpm@linux-foundation.org>, Oleg Nesterov <oleg@redhat.com>, Benjamin Poirier <bpoirier@suse.de>, Nagalakshmi Nandigama <nagalakshmi.nandigama@avagotech.com>, Praveen Krishnamoorthy <praveen.krishnamoorthy@avagotech.com>, Sreekanth Reddy <sreekanth.reddy@avagotech.com>, Abhijit Mahajan <abhijit.mahajan@avagotech.com>, Hariprasad S <hariprasad@chelsio.com>, Santosh Rastapur <santosh@chelsio.com>, "MPT-FusionLinux.pdl@avagotech.com" <MPT-Fusi>
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On Mon, Jul 28, 2014 at 03:46:32PM +0000, Yuval Mintz wrote:
> > Subject: Re: [PATCH 1/3] driver core: enable drivers to use deferred probe from
> > init
> > 
> > On Mon, Jul 28, 2014 at 03:12:11PM +0000, Yuval Mintz wrote:
> > > Perhaps this is a silly question, but what guarantees that the
> > > deferred probe list will actually be triggered, e.g., in case the
> > > delayed device is the last device in the system?
> > 
> > The dev->init_delayed_probe is used to ensure that we'd add the device to the
> > deferred probe list once making this a per device thing if the driver has the field
> > delay_probe set to true. This technically also allows this to be a per device thing
> > so with some more work we could enable drivers to only enable this for specific
> > devices but at this point this did not seem required.
> 
> Sorry for not being clear, but I didn't meant 'what guarantees that the device
> will be added to the deferred probe', but rather what guarantees that the
> deferred workqueue will be scheduled.
> 
> To the best of my knowledge the deferring mechanism works only if one device
> is dependent upon another, e.g., for Multi-function devices where one device
> probe is dependent upon the others - which are soon-to-be probed.

The workqueue will be kicked when driver_deferred_probe_trigger() gets
poked, we do that in the late_initcall(deferred_probe_initcall), it
also gets flushed there with a flush_workqueue(deferred_wq).

  Luis