17 Oct
2023
17 Oct
'23
11:23 a.m.
On 17.10.23 11:14, Ilias Apalodimas wrote:
Hi Heinrich,
On Tue, 17 Oct 2023 at 11:55, Heinrich Schuchardt <heinrich.schuchardt@canonical.com mailto:heinrich.schuchardt@canonical.com> wrote:
Forward and backward compatibility of Linux kernel device-trees is sometimes missing. One solution approach is to load a kernel specific device-tree. This can either be done via a U-Boot scripts (like the one generated by Debian package flash-kernel or by a boot loader like GRUB. The boot loader approach currently requires to know the device-tree name before first boot which makes it unusable for generic images. Expose the device-tree file name as EFI variable FdtFile. This will allow bootloaders to load a kernel specific device-tree. Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com <mailto:heinrich.schuchardt@canonical.com>> --- lib/efi_loader/efi_setup.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/lib/efi_loader/efi_setup.c b/lib/efi_loader/efi_setup.c index e6de685e87..b24feb94dc 100644 --- a/lib/efi_loader/efi_setup.c +++ b/lib/efi_loader/efi_setup.c @@ -26,6 +26,27 @@ void __weak allow_unaligned(void) { } +/** + * efi_init_fdtfile() - set EFI variable FdtFile + * + * Return: status code + */ +static efi_status_t efi_init_fdtfile(void) +{ + char *val; + + val = env_get("fdtfile"); + if (!val) + return EFI_SUCCESS; + + return efi_set_variable_int(u"FdtFile", + &efi_u_boot_guid, + EFI_VARIABLE_BOOTSERVICE_ACCESS | + EFI_VARIABLE_RUNTIME_ACCESS |Why is runtime access needed? Wouldn't the choice be done before ExitBootServices?
Having runtime access will allow to use the content of the variable to write a devicetree command to grub.cfg or to copy the relevant device-tree to a predefined location.
As GRUB cannot read EFI variables, yet, this would be the easiest short-term approach.
Best regards
Heinrich
[...]
Thanks /Ilias