Messages in this thread | | | Date | Sat, 07 Feb 2015 14:51:45 +0800 | From | Hanjun Guo <> | Subject | Re: [PATCH v8 08/21] dt / chosen: Add linux,uefi-stub-generated-dtb property |
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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
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