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There are several use cases for installing additional files in the boot
partition that is read by the RPi firmware.
- autoboot.txt is an optional configuration file for the RPi
firmware [1]. Supporting several autoboot files will enable A/B
setups, as using the renameat2() system call with the RENAME_EXCHANGE
flag will let users atomically replace one autoboot configuration
file with the other. This improves reliability in the case of an
update which could potentially be interrupted.
- Multiple cmdline.txt files are useful in the context of a new
[boot_partition] conditional filter introduced in config.txt in
commit [2]. This is useful for A/B systems to have identical BootFS
partitions on both slots, and not have to edit the kernel command line
to ensure the kernel will load the right rootFS after update of the
BootFS.
- rpi-firmware contains DTB overlays for many "standard" hats, but a
custom hat may require a custom overlay.
Although it is possible to install additional files in the boot
partition in the post-image script, it is very convenient to be able to
use the standard RPi post-image script in
board/raspberrypi/post-image.sh. That script looks in
$BINARIES_DIR/rpi-firmware, so it is convenient to be able to place
additional files there.
Add the option BR2_PACKAGE_RPI_FIRMWARE_EXTRA_FILES which is simply a
list of files to be copied to $BINARIES_DIR/rpi-firmware, which will
eventually end up as the boot partition. Make sure that this is done as
the last step of RPI_FIRMWARE_INSTALL_IMAGES_CMDS, so the files can
override files installed by earlier steps.
[1] https://www.raspberrypi.com/documentation/computers/config_txt.html#autoboot-txt
[2] d50b2b32f1
Signed-off-by: Olivier Benjamin <olivier.benjamin@bootlin.com>
Signed-off-by: Arnout Vandecappelle <arnout@rnout.be>
Buildroot is a simple, efficient and easy-to-use tool to generate embedded Linux systems through cross-compilation. The documentation can be found in docs/manual. You can generate a text document with 'make manual-text' and read output/docs/manual/manual.text. Online documentation can be found at https://buildroot.org/docs.html To build and use the buildroot stuff, do the following: 1) run 'make menuconfig' 2) select the target architecture and the packages you wish to compile 3) run 'make' 4) wait while it compiles 5) find the kernel, bootloader, root filesystem, etc. in output/images You do not need to be root to build or run buildroot. Have fun! Buildroot comes with a basic configuration for a number of boards. Run 'make list-defconfigs' to view the list of provided configurations. Please feed suggestions, bug reports, insults, and bribes back to the buildroot mailing list: buildroot@buildroot.org You can also find us on #buildroot on OFTC IRC. If you would like to contribute patches, please read https://buildroot.org/manual.html#submitting-patches