On Tue, 17 Oct 2023 at 12:23, Heinrich Schuchardt < [email protected]> wrote:
> On 17.10.23 11:14, Ilias Apalodimas wrote: > > Hi Heinrich, > > > > On Tue, 17 Oct 2023 at 11:55, Heinrich Schuchardt > > <[email protected] > > <mailto:[email protected]>> 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 > > <[email protected] > > <mailto:[email protected]>> > > --- > > 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. > > Do you mean to write EFI variables? If you want GRUB to be able to do that, wouldn't it be better to use a generic GUID instead of the U-Boot one? Regards /Ilias > Best regards > > Heinrich > > > > > > [...] > > > > > > Thanks > > /Ilias > >
