On 2015年02月07日 13:03, Ard Biesheuvel wrote:
On 7 February 2015 at 03:36, Hanjun Guo hanjun.guo@linaro.org wrote:
On 2015年02月06日 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?
As far as I remember, we did not finalize the decision to go with a stub generated property instead of some other means to infer that the device tree is not suitable for booting and ACPI should be preferred.
We will be discussing the 'stub<->kernel interface as a boot protocol' topic this week at Connect, so let's discuss it in that context before signing off on patches like these.
OK, see you guys in Hongkong.
Thanks Hanjun