[GIT PULL] On-demand device probing

[Rafael J. Wysocki]

On Wednesday, October 21, 2015 10:55:14 AM Geert Uytterhoeven wrote:
> Hi Rafael,
> 
> On Wed, Oct 21, 2015 at 1:34 AM, Rafael J. Wysocki <rjw at rjwysocki.net> wrote:
> > On Tuesday, October 20, 2015 09:15:01 AM Rob Herring wrote:
> >> On Tue, Oct 20, 2015 at 2:56 AM, Rafael J. Wysocki <rjw at rjwysocki.net> wrote:
> >> > ACPI uses platform devices too.  In fact, ACPI device objects are enumerated as
> >> > platform devices by default now.
> >>
> >> Okay, I should have grepped for that:
> >> drivers/base/platform.c:                ACPI_COMPANION_SET(&pdev->dev, NULL);
> >> drivers/base/platform.c:        len = acpi_device_modalias(dev, buf,
> >> PAGE_SIZE -1);
> >> drivers/base/platform.c:        rc = acpi_device_uevent_modalias(dev, env);
> >> drivers/base/platform.c:        /* Then try ACPI style match */
> >> drivers/base/platform.c:        if (acpi_driver_match_device(dev, drv))
> >>
> >> These are all cases which have DT version as well, so we're not really
> >> all that different here. There's a few more for DT, but that probably
> >> means you have just not hit the problems we have yet. For example,
> >> what happens if you have an interrupt line in which the controller is
> >> probed after the device connected to the interrupt line? That required
> >> resolving irqs in platform_get_irq rather than using static resources
> >> to support deferred probe.
> >
> > We don't have this particular problem, because the IRQ controllers are
> > enumerated in a special way.
> 
> What does "in a special way" mean? Can you please be more specific?
> 
> Can you have interrupt controllers that depend on clocks, pin controllers,
> and PM domains?

Currently, there's no native way to represent those dependencies in ACPI.

Thanks,
Rafael