On Thu, Jun 27, 2013 at 7:04 PM, Stephen Warren <swarren@xxxxxxxxxxxxx> wrote: > On 06/26/2013 01:31 PM, Leif Lindholm wrote: >> On Wed, Jun 26, 2013 at 12:32:30PM -0600, Stephen Warren wrote: >>>>> What about ARMv8? Is the intention to have a separate definition for the >>>>> UEFI bindings on ARMv8, so that compatibility isn't an issue? What if a >>>>> future version of UEFI allows LPAE usage? >>>> >>>> It is unlikely that will happen on v7 since newer versions of UEFI are >>>> expected to remain backwards compatible with the current spec. >>> >>> The expectation of backwards-compatibility sounds nice, but it seems a >>> little dangerous to outright rely on it. >>> >>> Even if not a regular compatible property, can we define a property that >>> indicates the UEFI revision or revision of this DT binding, so that if >>> we ever have to change it, there is some way of explicitly indicating >>> which exact schema the DT corresponds to, rather than having to >>> reverse-engineer it from the set of properties that "just happen" to be >>> present in DT? >>> >>> This is rather like the firmware node discussion that happened recently, >>> where we were expecting to represent a firmware (secure mode) interface >>> by a DT node, which would have a compatible value, which in turn would >>> convey information about which "OS" the secure firmware was running, and >>> well as any potential SoC-/OEM-/board-specific interface provided by it. >>> >>> And who knows, what if UEFI gets replaced someday; presumably we'd want >>> some way of explicitly stating "running under UEFI" vs. "running under >>> something else"? >> >> To me, these concerns are all covered by the existence of the >> efi-system-table node, and the version number that you can extract >> from the table (mandatory in any UEFI implementation) located at that >> address. There is no reverse-engineering involved. > > So, what you're saying is that the existence (or lack thereof) of the > efi-system-table property is the indicator whether EFI is present? I > guess if we assume that EFI will always evolve at least compatibly > enough that the system table will always exist and be formatted > identically at least to the extent of allowing the EFI version number to > be parsed then that's workable. If that guarantee is broken, then we can > always define a different property that points at the new format of the > table. Yes, that is what it means, and there is *immense* pressure from the OEM market to not break that contract in a non-backwards-compatible way. g. -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
