syntax = "proto3";

package metropolis.node.abloader.spec;

enum Slot {
    SLOT_NONE = 0;
    SLOT_A = 1;
    SLOT_B = 2;
}

// ABLoaderData contains data the A/B loader needs to chose which slot to boot
// as well as for auto-rollback functionality.
message ABLoaderData {
    // The currently-active slot. This slot will be booted unless next_slot is
    // set to a non-default value.
    Slot active_slot = 1;
    // The slot to boot next, but only once. Once the the slot has been selected
    // to be booted by the loader, this value is reset before booting into that
    // slot. If the OS boots successfully, it will update the active_slot to
    // permanently boot from the new slot.
    Slot next_slot = 2;
}