[PATCH 1/1] efi_loader: expose the device-tree file name

[Ilias Apalodimas]

Hi Heinrich,

On Tue, 17 Oct 2023 at 11:55, Heinrich Schuchardt <
heinrich.schuchardt at 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 at 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?

[...]


Thanks
/Ilias