Add a description how to embed the bootconfig file into kernel. Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx> --- Documentation/admin-guide/bootconfig.rst | 31 +++++++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst index a1860fc0ca88..a172c669997a 100644 --- a/Documentation/admin-guide/bootconfig.rst +++ b/Documentation/admin-guide/bootconfig.rst @@ -158,9 +158,15 @@ Each key-value pair is shown in each line with following style:: Boot Kernel With a Boot Config ============================== -Since the boot configuration file is loaded with initrd, it will be added -to the end of the initrd (initramfs) image file with padding, size, -checksum and 12-byte magic word as below. +There are 2 options to boot the kernel with bootconfig, one is attaching +bootconfig to initrd image, and embedding the kernel itself. + +Attaching a Boot Config to Initrd +--------------------------------- + +Since the boot configuration file is loaded with initrd by default, +it will be added to the end of the initrd (initramfs) image file with +padding, size, checksum and 12-byte magic word as below. [initrd][bootconfig][padding][size(le32)][checksum(le32)][#BOOTCONFIG\n] @@ -196,6 +202,25 @@ To remove the config from the image, you can use -d option as below:: Then add "bootconfig" on the normal kernel command line to tell the kernel to look for the bootconfig at the end of the initrd file. +Embedding a Boot Config into Kernel +----------------------------------- + +If you can not use initrd, you can also embed the bootconfig file to the +kernel by Kconfig options. In This case, you need to recompile the kernel +with the following configs:: + + COFNIG_EMBED_BOOT_CONFIG=y + CONFIG_EMBED_BOOT_CONFIG_FILE="/PATH/TO/BOOTCONFIG/FILE" + +You need to set the correct path (relative path from kernel build directory +or absolute path) to the ``CONFIG_EMBED_BOOT_CONFIG_FILE`` option. +Then the kernel will embed the bootconfig file as a default bootconfig. + +As same as attaching to initrd, you need ``bootconfig`` option to the +kernel command line to enable the embedded bootconfig. + +Note that even if you set this option, you can override the embedded +bootconfig by another bootconfig which attached to the initrd. Kernel parameters via Boot Config =================================
