Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH 02/13] driver-core: defer all probes until late_initcall | Date | Wed, 24 Jun 2015 02:14:30 +0200 |
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On Tuesday, June 23, 2015 04:37:57 PM Tomeu Vizoso wrote: > On 23 June 2015 at 16:51, Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > > On Tuesday, June 23, 2015 04:17:29 PM Tomeu Vizoso wrote: > >> On 23 June 2015 at 16:37, Rafael J. Wysocki <rjw@rjwysocki.net> 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 <rjw@rjwysocki.net> wrote: > >> >> > On Friday, June 19, 2015 03:36:46 PM Tomeu Vizoso wrote: > >> >> >> On 18 June 2015 at 23:50, Rafael J. Wysocki <rjw@rjwysocki.net> 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 <tomeu.vizoso@collabora.com> > >> >> >> >> --- > >> >> >> >> 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? > > Would it help if buses called fwnode_driver_match_device() instead of > the existing OF and ACPI variants and we did it in there?
Probably it would, but I'd need to see the actual patch. :-)
> I'm still not sure of how fwnode is used in machines with ACPI.
I'm not sure what you mean. On ACPI systems struct fwnode_handle is embedded in struct acpi_device and there is a pointer from struct device to that field in the companion ACPI device object.
> But that would be quite a bit of work that I think should be left for > a later series because otherwise this one is going to balloon in size > really quickly.
Well, I'd prefer not to leave anything to a "later series" that may never be submitted ...
> > 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. > > I would expect that classes/subsystems would be able to use that data > in their class.get_dependencies() callback, if the passed fwnode is a > ACPI node.
Yes, something like that.
But the point is that this really isn't OF-specific.
Thanks, Rafael
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