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.schucha...@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 |
+ EFI_VARIABLE_READ_ONLY,
+ strlen(val) + 1, val, false);
+}
+
/**
* efi_init_platform_lang() - define supported languages
*
@@ -250,6 +271,11 @@ efi_status_t efi_init_obj_list(void)
if (ret != EFI_SUCCESS)
goto out;
+ /* Define EFI variable FdtFile */
+ ret = efi_init_fdtfile();
+ if (ret != EFI_SUCCESS)
+ goto out;
+
/* Indicate supported features */
ret = efi_init_os_indications();
if (ret != EFI_SUCCESS)
--
2.40.1
