Heads up, #OpenBSD -current is preparing for >16 partition disklabels (increased to 52). If you're not using sysupgrade(8), and manually upgrading, you need to pay special attention to this change.

deraadt@ modifed src/sys/*: Begin transition to 52-partition support. The partition encoding used to be lowest 4 bits of dev_t, and now becomes 6. This supplies 64 partitions in struct disklabel.d_partitions[MAXPARTITIONSUNIT], but we only use 52 of these slots (an architecture can be either 16 partition or 52 partition, depending on MD define MAXPARTITIONS). The 52-partition limit is due to single-character representation limit of a-zA-Z. We supply a backwards-compat ioctl for a while which can read an disklabel structure.

This change does not yet store 52-partition information on-disk, and does not transition any architecture to allowing use of >16 partitions.
Those changes come soon, after this compatibility breaking change settles.

Immediate result is dev_t numbers for /dev/{sd,wd,rd,fd,...}[12345...][a-p] become incorrect, and need to be repaired. A sysupgrade will do this for automatically. For a hand-build, or a manual kernel replacement, systems which have root NOT ON SD0 or WD0, probably fail into single-user and you must perform these steps explained in /etc/rc:

# fsck /dev/rrootdisk
# mount -uw /dev/rootdisk /
# cd /dev && ./MAKEDEV redodisks

Please do not try to manual-build through this on a system earlier than 7.8.

with and ok krw