s/PG_XIP/PQ_FIXED/, meaning that the fault handler sees XIP pages as
"fixed", and doesn't pass them to paging activity.

("XIP" is a vnode specific knowledge.  It was wrong that the fault
handler had to know such a special thing.)
Cosmetic.
Remove a useless assertion.
Give "physseg" related functions better names.
After much consideration, rename bus_space_physload_direct(9) back to
bus_space_physload_device(9).

The latter registers a segment as "device pages".  "Device pages" are
managed, but not used for general purpose memory.  Most typically XIP
pages.
s/DIOCGPHYSADDR/DIOCGPHYSSEG/ now that it returns struct vm_physseg *,
not paddr_t.
Use VM_PROT_* instead of PROT_* in UVM.
Correct bus_space_physload(9) arguments to take "int freelist".

A possible use case of bus_space_physload(9) would be some high-performance
device with huge local memory, like InfiniBand HCA.  We can register
its local memory using bus_space_physload(..., VM_FREELIST_INFINIBAND0),
then later map it to userspace via cdev_mmap(9) -> bus_dmamem_mmap(9).

(bus_dma(9) needs changes too, of course.)
Document bus_space_physload(9), bus_space_physunload(9),
bus_space_physload_device(9), and bus_space_physunload_device(9).
Minimal documentation of flash(4).
Document options XIP.
s/vm_physseg_find_direct/vm_physseg_find_device/
If both __HAVE_PMAP_PHYSSEG and __HAVE_PMAP_PHYSSEG_INIT is defined,
call per-vm_physseg initialization/finalization hooks.
Support bus_space_physload(9) and friends.
Export flash_init() correctly.  Calculate disk partition correctly.
Correct dmesg.  Correct conditional compilation.
Support files other than kernel executables.

For filesystem images, embed (not prepend) OpenBIOS image headers to
the images, so that alignment is kept in the resulting files.
In XIP vnode pager, assert that filesystem blocks and pages are aligned.
Support XIP; look up "device" vm_physseg for managed pages.  Initialize
vm_physseg MD part.
Hook pmap_physseg_{init,fini} on powerpc/ibm4xx.
Implement 405GPr's "External Bus" as exb(4).