[PATCH 6/6 v2] doc: Update uefi documentation for initrd loading options

Ilias Apalodimas ilias.apalodimas at linaro.org
Sat Mar 13 22:47:37 CET 2021

Document the command line options for efidebug and initrd loading

Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
 doc/uefi/uefi.rst | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/doc/uefi/uefi.rst b/doc/uefi/uefi.rst
index b3494c22e073..76402bc5cfaa 100644
--- a/doc/uefi/uefi.rst
+++ b/doc/uefi/uefi.rst
@@ -180,6 +180,12 @@ Set up boot parameters on your board::
     efidebug boot add -b 1 HELLO mmc 0:1 /helloworld.efi.signed ""
+Since kernel 5.7 there's an alternative way of loading an initrd using
+LoadFile2 protocol if CONFIG_EFI_LOAD_FILE2_INITRD is enabled.
+The initrd path can be specified with::
+    efidebug boot add -b ABE0 'kernel' mmc 0:1 Image -i mmc 0:1 initrd
 Now your board can run the signed image via the boot manager (see below).
 You can also try this sequence by running Pytest, test_efi_secboot,
 on the sandbox
@@ -484,7 +490,20 @@ The load file 2 protocol can be used by the Linux kernel to load the initial
 RAM disk. U-Boot can be configured to provide an implementation with::
-    EFI_INITRD_FILESPEC=interface dev:part path_to_initrd
+When the options is enabled the user can add the initrd path with the efidebug
+The Boot#### option has a FilePathList[] in it's EFI_LOAD_OPTION.
+The first element of the array (FilePathList[0]) is the loded image.
+When an initrd is specified the Device Path for the initrd is denoted by a
+VenMedia node with the EFI_INITRD_MEDIA_GUID. Each entry of the array is
+terminated by the 'end of entire device path' subtype. If the user wants to
+define multiple initrds those must by separated by the 'end of this instance'
+identifier of the end node (0x01).
+So our final format of the FilePathList[] is::
+    Loaded image - end node (0xff) - VenMedia - initrd1 - end node (0x01) initrd2 - end node (0xff)

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