Messages in this thread | | | Date | Mon, 28 Jul 2014 17:38:11 +0200 | From | "Luis R. Rodriguez" <> | Subject | Re: [PATCH 1/3] driver core: enable drivers to use deferred probe from init |
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On Mon, Jul 28, 2014 at 03:12:11PM +0000, Yuval Mintz wrote: > > +static int __driver_probe_device(struct device_driver *drv, struct > > +device *dev) { > > + if (drv->delay_probe && !dev->init_delayed_probe) { > > + dev_info(dev, "Driver %s requests probe deferral on init\n", > > + drv->name); > > + dev->init_delayed_probe = true; > > + driver_deferred_probe_add(dev); > > + return -EPROBE_DEFER; > > + } > > + > > + return really_probe(dev, drv); > > +} > > 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.
> [From drivers/base/dd.c - "A successful driver probe will trigger moving all > devices from the pending to the active list so that the workqueue will > eventually retry them]
I had not noticed this, thanks for pointing this out, in this case if __driver_probe_device() is still used to retrigger a probe it will be added back to the deferred list but since dev->init_delayed_probe is still false. I checked the original commit that added this feature d1c3414c but in the code I see that bus_probe_device(dev) is used and I only see the device itself being removed from the deferred probe list, nothing else.
Luis
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