On Tuesday, June 23, 2015 04:17:29 PM Tomeu Vizoso wrote: > On 23 June 2015 at 16:37, Rafael J. Wysocki <[email protected]> wrote: > > On Monday, June 22, 2015 07:07:08 PM Rob Herring wrote: > >> On Fri, Jun 19, 2015 at 6:20 PM, Rafael J. Wysocki <[email protected]> > >> wrote: > >> > On Friday, June 19, 2015 03:36:46 PM Tomeu Vizoso wrote: > >> >> On 18 June 2015 at 23:50, Rafael J. Wysocki <[email protected]> wrote: > >> >> > On Wednesday, June 17, 2015 03:42:12 PM Tomeu Vizoso wrote: > >> >> >> To decrease the chances of devices deferring their probes because of > >> >> >> dependencies not having probed yet because of their drivers not > >> >> >> having > >> >> >> registered yet, delay all probing until the late initcall level. > >> >> >> > >> >> >> This will allow us to avoid deferred probes completely later by > >> >> >> probing > >> >> >> dependencies on demand, or by probing them in dependency order. > >> >> >> > >> >> >> Signed-off-by: Tomeu Vizoso <[email protected]> > >> >> >> --- > >> >> >> drivers/base/dd.c | 8 +++++++- > >> >> >> 1 file changed, 7 insertions(+), 1 deletion(-) > >> >> >> > >> >> >> diff --git a/drivers/base/dd.c b/drivers/base/dd.c > >> >> >> index a638bbb..18438aa 100644 > >> >> >> --- a/drivers/base/dd.c > >> >> >> +++ b/drivers/base/dd.c > >> >> >> @@ -407,6 +407,12 @@ int driver_probe_device(struct device_driver > >> >> >> *drv, struct device *dev) > >> >> >> if (!device_is_registered(dev)) > >> >> >> return -ENODEV; > >> >> >> > >> >> >> + /* Defer all probes until we start processing the queue */ > >> >> >> + if (!driver_deferred_probe_enable) { > >> >> >> + driver_deferred_probe_add(dev); > >> >> > > >> >> > Do I think correctly that this will effectively force everybody to > >> >> > use deferred > >> >> > probing? > >> >> > >> >> Guess it depends on the meaning of "using deferred probing". It will > >> >> defer the probe of the first device to late_initcall (which will > >> >> happen much earlier in time than before), but afterwards all built-in > >> >> drivers will be available and depending on the order in which we try > >> >> to probe devices, none may actually ask to defer its probe. > >> > > >> > So this will break things like the PNP system driver which relies on > >> > probing > >> > stuff at the fs_initcall stage for correctness. It may also break other > >> > things with similar assumptions. > >> > >> Yes, but I think that this can be done for only OF based devices > >> rather than globally for all platform devices and solve that problem. > >> Matching is already dependent of the type of device. > > > > Well, the current patch is not OF-only, though. > > Yeah, I'm currently looking at only delaying probing of devices > created from OF data.
I'm not sure if tying it hard to OF is not too restrictive. Maybe we can use some general opt-in mechanism that OF will just always use? In fact, we have a similar problem in ACPI where we have the _DEP object which is used by firmware to describe dependencies between devices. > Note that calculating dependencies and trying to probe them before > they are needed can be done independently of this patch, but it isn't > that useful because devices will still defer their probes because the > drivers of some dependencies won't have been registered until > late_initcall. I see. Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
