Re: [PATCH 1/3] driver core: enable drivers to use deferred probe from init

Luis R. Rodriguez
2014-07-28T16:52:48Z

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