From mboxrd@z Thu Jan 1 00:00:00 1970 From: hanjun.guo@linaro.org (Hanjun Guo) Date: Sat, 07 Feb 2015 11:36:42 +0800 Subject: [PATCH v8 08/21] dt / chosen: Add linux,uefi-stub-generated-dtb property In-Reply-To: References: <1422881149-8177-1-git-send-email-hanjun.guo@linaro.org> <1422881149-8177-9-git-send-email-hanjun.guo@linaro.org> <20150202134033.GR4278@bivouac.eciton.net> <20150202135051.GA3825@xora-haswell.xora.org.uk> <20150202163253.GG21175@leverpostej> Message-ID: <54D5884A.6050009@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 2015?02?06? 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