On Tue, Nov 19, 2013 at 02:38:40PM +0000, Mark Rutland wrote: > > > For that case we will also require a nailed-down boot > > > protocol that allows for either DTB or ACPI. > > > > The latest documentation patch for the "arm/arm64 UEFI boot protocol" > > implies that UEFI on ARM is already capable of passing a DTB to the > > kernel: > > > > "The implementation depends on receiving information about the UEFI > > environment in a Flattened Device Tree (FDT) - so is only available with > > CONFIG_OF." > > > > Maybe we just need to better document it? > > Yes, we just need to document it. Better document it than what is currently in Booting? > As far as I'm aware, there are two ways we might boot the kernel: Nope, just one. > 1) Via the current boot protocol, passing a DTB in a particular > register. This is the only bit relevant to the kernel proper. It does not change with UEFI/ACPI. > 2) As an EFI application. As I understand it in this case the DTB will > be saved in a system table (I may have got the terminology wrong here), > and the EFI stub will need to look it up to pass it to the kernel. This applies only to the stub itself, and relates to dealing with a firmware that provides a preloaded tree. As well as an obscurity relating to _stub_ command line passing. It has also not been included in the patch sets sent out so far. > As long as that's well defined and does not preclude ACPI, then I am > happy. This is already well defined. I'll agree it may not be explicit enough. If we do need any documentation changes, I feel they belong in Booting, to explain that a minimal DT will be used even with ACPI in order _not_ to break the existing boot protocol. / Leif -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html