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?
Martyn