Introduce bus_get_bus_tag() method

Provide bus_get_bus_tag() for sparc64, powerpc, arm, arm64 and mips
nexus and its children in order to return a platform specific default tag.

This is required to ensure generic correctness of the bus_space tag.
It is especially needed for arches where child bus tag does not match
the parent bus tag. This solves the problem with ppc architecture
where the PCI bus tag differs from parent bus tag which is big-endian.

This commit is a part of the following patch:
https://reviews.freebsd.org/D4879

Submitted by:  Marcin Mazurek <mma@semihalf.com>
Obtained from: Semihalf
Sponsored by:  Annapurna Labs
Reviewed by:   jhibbits, mmel
Differential Revision: https://reviews.freebsd.org/D4879

0 files changed, 0 insertions, 0 deletions