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

[Heinrich Schuchardt]

On 3/13/21 10:47 PM, Ilias Apalodimas wrote:

Document the command line options for efidebug and initrd loading

Signed-off-by: Ilias Apalodimas <ilias.apalodi...@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_LOAD_FILE2_INITRD=y
-    EFI_INITRD_FILESPEC=interface dev:part path_to_initrd

Thanks for adding the description. Some nitpicky comments below:

+
+When the options is enabled the user can add the initrd path with the efidebug

%s/options/option/

+command.
+The Boot#### option has a FilePathList[] in it's EFI_LOAD_OPTION.

Load options Boot#### have a FilePathList[] member.

+The first element of the array (FilePathList[0]) is the loded image.

is the EFI binary to execute.

+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

Below you have (0x01). So add (0xff) here.

+define multiple initrds those must by separated by the 'end of this instance'

%s/initrds/initrds,/

+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)

Loaded image - end node (0xff) - VenMedia - initrd_1 -
[end node (0x01) - initrd_n ...] - end node (0xff)

There can be any number of initrds?

Best regards

Heinrich

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