On 11 August 2015 at 11:37, Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx> wrote: > On 7 August 2015 at 14:19, Mark Brown <broonie@xxxxxxxxxx> wrote: >> On Thu, Aug 06, 2015 at 04:11:39PM +0200, Tomeu Vizoso wrote: >> >>> Walks the OF tree up and finds the closest ancestor that has a platform >>> device associated with it, probing it if isn't bound to a driver yet. >> >>> The above should ensure that the dependency represented by the passed OF >>> node is available, because probing a platform device should cause its >>> descendants to be probed as well. >> >> This sounds like it's going to break in the case where we have MFDs that >> represent their functions in DT (not a pattern I'm a fan of but it's a >> thing people do). We'll walk back to the platform device for the MFD >> function, try to probe it and then give up. Perhaps that's good enough >> anyway but it's not clear to me why we don't just try every parent we >> find? > > Agreed. In the attempt at probing dependencies before a device is > probed, I considered that a device's parent is also a dependency and > that worked well. From what I saw, few devices will defer their probe > if their parent hasn't been probed yet, assuming that it will have > probed already. But with simple-mfd and simple-bus that shouldn't be > relied upon as things will break if their parents defer their probe. > With async probing enabled this failure scenario becomes more > probable. Actually I'm not sure how we could probe the ascendants on demand, as currently the parent's device lock is taken when probing so trying to probe a sibling from within a probe callback will cause a deadlock. AFAICS this is only needed for USB interface devices and this behaviour could be limited to them, but I don't like much assuming that no USB device will ever have a dependency on a sibling (though that probably won't happen ever). Regards, Tomeu >> I'm also not a fan of the fact that the interface here is explicitly >> saying that we want to probe a platform device, that's an implementation >> detail that callers shouldn't need to know about. From the point of >> view of the callers what they're trying to do is kick any dependencies >> into being instantiated, the fact that we currently try to accomplish it >> with platform devices isn't something they care about. > > Agreed. > > Thanks, > > Tomeu -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
