From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hanjun Guo Subject: Re: [PATCH v8 08/21] dt / chosen: Add linux,uefi-stub-generated-dtb property Date: Sat, 07 Feb 2015 14:51:45 +0800 Message-ID: <54D5B601.60807@linaro.org> 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> <54D5884A.6050009@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Ard Biesheuvel Cc: G Gregory , Mark Rutland , Leif Lindholm , Mark Langsdorf , "linaro-acpi@lists.linaro.org" , Catalin Marinas , Will Deacon , "wangyijing@huawei.com" , Rob Herring , Lorenzo Pieralisi , Jonathan Corbet , Timur Tabi , Daniel Lezcano , "linux-acpi@vger.kernel.org" , "grant.likely@linaro.org" , Charles Garcia-Tobin , "phoenix.liyi@huawei.com" , Robert Richter , Jason Cooper , Arnd Bergmann , Marc Zyngier List-Id: linux-acpi@vger.kernel.org On 2015=E5=B9=B402=E6=9C=8807=E6=97=A5 13:03, Ard Biesheuvel wrote: > On 7 February 2015 at 03:36, Hanjun Guo wrote= : >> On 2015=E5=B9=B402=E6=9C=8806=E6=97=A5 18:34, G Gregory wrote: >> [...] >> >>>>>>> >>>>>>> ---------------------------------------------------------------= ----------------- >>>>>>> linux,uefi-stub-kern-ver | string | Copy of linux_banner fr= om >>>>>>> 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 th= e >>>>>> absence of a registered UEFI configuration table as the indicati= on >>>>>> that no HW description was provided from firmware, since the stu= b does >>>>>> not call InstallConfigurationTable() on the DT it generates. Thi= s 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 stuf= f from >>>> Xen to the kernel in this case? When we initially discussed the st= ub >>>> 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 rat= her >>>>>> than the route we took to get there. >>>>>> >>>>> I agree. >>>> >>>> >>>> I guess this would be ok, though it would be nice to know which ag= ent >>>> generated the DTB. >>>> >>> >>> The most obvious scheme then is >>> >>> linux,bare-dtb =3D "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 befor= e > signing off on patches like these. OK, see you guys in Hongkong. Thanks Hanjun