On Thu, Oct 03, 2024 at 10:00:33AM +0100, Martyn Welch wrote:
On Wed, 2024-10-02 at 13:16 -0600, Tom Rini wrote:
On Wed, Oct 02, 2024 at 02:26:30PM +0100, Martyn Welch wrote:
When configured correctly, we can detect when boot fails after the boot process has been handed over to the kernel through the use of U- Boot's bootcount support. In some instances, such as when we are performing atomic updates via a system such as OSTree, it is desirable to provide a fallback option so that we can return to a previous (hopefully working) state.
Add a "fallback" option to the supported extlinux configuration options that points to a label like "default" so that we can utilise this in later commits.
Signed-off-by: Martyn Welch martyn.welch@collabora.com
Is "fallback" part of the nominal extlinux specification?
When looking at options to implement this functionality, I did spend some time looking for an extlinux specification. The best I could find was:
https://wiki.syslinux.org/wiki/index.php
Putting aside the difference in syntax from that used by the syslinux project, of the 22 keywords currently supported by U-Boot, only 13 of them are mentioned there (surprisingly the syslinux documentation doesn't include "title" as an option).
I'd come to the conclusion that U-Boot already provides a greatly extended version of the syntax, made suitable for booting in a wider variety of instances than catered for by the syslinux project.
Though I admit, I could have missed another better source to documentation. Is that the one you're thinking of or is there a better one?
I was thinking of https://systemd.io/BOOT_LOADER_SPECIFICATION/ which is now https://uapi-group.org/specifications/specs/boot_loader_specification/ and only has 11 keywords. So, yeah, I guess this is another place where we'll keep doing what's needed to make things more useful and see what happens down the road. I'm fine with what's being added in this series. Thanks!