Re: [PATCH v8 08/21] dt / chosen: Add linux,uefi-stub-generated-dtb property

[Hanjun Guo]

On 2015å02æ06æ 18:34, G Gregory wrote:
[...]
> > > > >   --------------------------------------------------------------------------------
> > > > >   linux,uefi-stub-kern-ver  | string | Copy of linux_banner from build.
> > > > >   --------------------------------------------------------------------------------
> > > > > +linux,uefi-stub-generated-dtb  | bool | Indication for no DTB provided by
> > > > > +                        |      | firmware.
> > > > > +--------------------------------------------------------------------------------
> > > >
> > > > Apologies for the late bikeshedding, but the discussion on this topic
> > > > previsously was lively enough that I thought I'd let it die down a bit
> > > > before seeing if I had anything to add.
> > > >
> > > > That, and I just realised something:
> > > > One alternative to this added DT entry is that we could treat the
> > > > absence of a registered UEFI configuration table as the indication
> > > > that no HW description was provided from firmware, since the stub does
> > > > not call InstallConfigurationTable() on the DT it generates. This does
> > > > move the ability to detect to after efi_init(), but this should be
> > > > fine for ACPI-purposes.
> > > That would not work as expected in the kexec/Xen use case though as they
> > > may genuinely boot with DT from an ACPI host without UEFI.
> >
> > I'm a little concerned by this case. How do we intend to pass stuff from
> > Xen to the kernel in this case? When we initially discussed the stub
> > prior to merging, we weren't quite sure if ACPI without UEFI was
> > entirely safe.
> >
> > The linux,uefi-stub-kern-ver property was originally intended as a
> > sanity-check feature to ensure nothing (including Xen) masqueraded as
> > the stub, but for some reason the actual sanity check was never
> > implemented.
> >
> > > > If that is deemed undesirable, I would still prefer Catalin's
> > > > suggested name ("linux,bare-dtb"), which describes the state rather
> > > > than the route we took to get there.
> > > I agree.
> >
> > I guess this would be ok, though it would be nice to know which agent
> > generated the DTB.
>
> The most obvious scheme then is
>
> linux,bare-dtb = "uefi-stub";
>
> otherwise we generate a new binding for every component in the boot path.

Leif, Mark, any comments on this?

Thanks
Hanjun
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