Hi-- On 3/13/22 06:56, Masami Hiramatsu wrote: > 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. There are two options to boot the kernel with bootconfig: attaching the bootconfig to the initrd image or embedding it in 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 in the > +kernel by Kconfig options. In This case, you need to recompile the kernel this > +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 Just as when attaching the bootconfig to the 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 > ================================= > HTH. -- ~Randy