[PATCH] arm64: defconfig: enable EFI_ARMSTUB_DTB_LOADER
From: Ard Biesheuvel <hidden>
Date: 2018-09-09 15:55:59
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On 9 September 2018 at 13:07, Catalin Marinas [off-list ref] wrote:
On Wed, Sep 05, 2018 at 11:04:36AM -0700, Scott Branden wrote:quoted
On 18-09-05 11:00 AM, Grant Likely wrote:quoted
On Wed, Sep 5, 2018 at 6:27 PM Scott Branden [off-list ref] wrote:quoted
On 18-09-05 02:40 AM, Ard Biesheuvel wrote:quoted
On 4 September 2018 at 19:19, Scott Branden [off-list ref] wrote:quoted
Rather than introduce EFI_ARMSTUB_DTB_LOADER, why not have the efistub use CONFIG_OF to determine whether it supports dtb= or not? That way ACPI-only distros disable devicetree support entirely.Unfortunately, CONFIG_OF cannot be disabled on arm64 even on ACPI-only builds.OF shouldn't be automatically selected in the arm64/Kconfig. It should have a config parmaeter like other archs as mips and arm. I can submit a patch so it functions the same way as other archs so it is not always selected. It will be good to add a USE_OF config options like the other archs (or simply remove the select from the Kconfig and choose OF directly in the defconfig. This will have the added benefit of doing away with OF support when its not needed on an ARM64 platform. ACPI is already not automatically selected for all ARM64 platforms, nor should devicetree.We don't do that on Arm because a devicetree is always required at boot time. Even on ACPI systems a tiny DTB is used containing just a /chosen node for passing the kernel command line and the initrd location.Seems bizarre DTB is not needed for x86 to boot from UEFI with ACPI support? I'll look into it further at some point in order to remove such anomaly. There should be no need for such devicetree reliance.I'd say don't waste time on this, the patch would not get merged ;). As Grant said, we use a tiny dtb to pass the command line, initrd to the kernel. You'd have to invent an alternative (setup_header, ATAGs) and I really don't see the point of increased complexity just because of some philosophical arguments against OF.
Not just that: we also need of_match_table support for ACPI's PRP0001 device (which is a horrible hack in itself, but currently supported in Linux/arm64 *and* Linux/x86 nonetheless)