Can't set program_usb_boot_mode pi-config option

[Sergey Borovkov]

It allows to boot from usb. Core allows it but currently there is no way to set it. Oliver suggested this on this PR https://github.com/snapcore/core/pull/38#issuecomment-299859765

>given that this option permanently changes the ROM code i'm not sure we should expose it in a generic config option you can run on any Pi.
i'd recommend to rather ship it in the gadget config.txt for this specific device and make the config-option carry over that setting when re-generating config.txt if it exists.

[Kyle Nitzsche (knitzsche)]

What is the status of this bug? It was filed by a client project developer and I'd like to know if it is fixed, invalid, etc. Cheers.

[Oliver Grawert (ogra)]

this should simply be set in their gadget snap in the original config.txt. the bootloader will apply it before the first boot (where potentially the config.txt gets re-written by the core config hook)

[Simon Fels (morphis)]

@Sergey, Kyle: Would Oliver's suggestion help to solve your issue?

[Kyle Nitzsche (knitzsche)]

Sergey asked whether this would require two gadget snaps: one for device that boot from usb, one from devices that work from sd.

Only one gadget snap would seem to be needed IF there is a boot fallback: try usb, else try sdd.

Does this solution use such a fallback?

[Zygmunt Krynicki (zyga)]

I just checked that program_usb_mode is indeed not surfaced through snappy configuration. Having said that, it feels like a weird configuration, especially since it is one-way-fuse that is being programmed.

I'm marking it as confirmed / medium but I think it warrants more discussion on how it should be exposed.