> In which OpenBSD file do I define the major number for devices (both
quoted text
> regular and pseudo-device)? I have searched in several sources, and
> the closest answer was for NetBSD, which says that major numbers are
> in /usr/src/sys/conf/majors. But I have not found this file in OpenBSD
> sources.

Noone builds new block devices anymore (in OpenBSD, we instead write
drivers which hide behind the scsi subsystem, since this is more
flexible).

As for strictly character devices, these are inserted per-architecture
into the cdevsw[] arrays in arch/ARCH/ARCH/conf.c.  At the same time,
/usr/src/etc/etc.ARCH/MAKEDEV* have to be modified to create the
device nodes.

There is no need to keep the major numbers in sync between different
architectures.  Actually because of many historical reasons, it is
impossible.