On Wed, Jan 30, 2019 at 9:33 AM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
>
> Hi,
>
> On 29-01-19 23:41, Rafael J. Wysocki wrote:
> > On Fri, Jan 25, 2019 at 11:47 AM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
>
> <big snip>
>
> >>> I wonder if we could just defer the enumeration of devices with _DEP
> >>> underneath. That is, evaluate _DEP before calling
> >>> acpi_bus_type_and_status() in acpi_bus_check_add() and, if present and
> >>> non-empty, put the handle onto a "to be inspected later" list, skip it
> >>> along with everything below it and only get back to it when we have
> >>> enumerated all stuff without _DEP. [And don't do that for devices on
> >>> the PCI bus.]
> >>
> >> I agree with you that ideally we would honor _DEP during enumeration
> >> and skip enumeration of devices (and their children) with a _DEP which
> >> lists unmet dependencies.
> >
> > This is not exactly what I'm talking about, however.
> >
> > The idea is to defer the enumeration of devices with non-empty _DEP
> > (that is, non-empty after taking some known pathological cases into
> > account) and their children until all of the devices without _DEP have
> > been enumerated.
>
> Nitpick, I assume that enumerated above includes having acpi_bus_attach()
> called on them.
Yes, it does.
> Ah, rereading your original proposal I understand what you want to do now.
> Yes I think that will work for the problematic cases I am aware of
> (which is mostly the one from this thread).
>
> But I think if we're going to do this, it would be better to have
> something like this:
>
> walk-tree, adding devices where all _DEP dependencies are met (or there are none),
> add devices with missing deps to a to-be-enumerated list.
> acpi_bus_attach(acpi_root)
>
> while (1) {
> number_of_enumerated_devices = 0;
> for-each-handle-on-to-be-enumerated-list {
> dep_ok = check_DEP()
That would return 'false' until the acpi_bus_attach() below runs,
however, because that's when the drivers that install opregion
handlers are attached to devices. That's one of the reasons why the
problem is kind of tricky.
> if (dep_ok) {
> add-device()
> number_of_enumerated_devices++
> }
> }
> if (number_of_enumerated_devices == 0)
> break;
> acpi_bus_attach(acpi_root)
> }
>
> number_of_enumerated_devices = 0;
> for-each-handle-on-to-be-enumerated-list {
> add-device()
> number_of_enumerated_devices++
> }
>
> if (number_of_enumerated_devices)
> acpi_bus_attach(acpi_root)
>
> I believe that this is pretty close to your proposal, except that
> it tries to also honor nested _DEP-s, while still adding all
> devices independent of _DEP at the end.
Nested _DEPs could be addressed in a different way, I think, but I'm
not sure if they are a concern in practice.
