Hi Randy, Thanks for the review and fix! I also found that CONFIG_EMBED_BOOT_CONFIG_FILE should be an absolute path (for example, if the kernel is built with O=DIR option, the relative path will be interpreted from the build directory (DIR/lib) but that is too complicated.) So I'll update this document. Thank you! On Sun, 13 Mar 2022 10:52:35 -0700 Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote: > 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 -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
