some kernel hacking tasks

[Sepherosa Ziehau]

Hi all,

I have several kernel hacking tasks; any helping hands are welcome.
- Replace bpf's mplock w/ its own token
- Support busdma(9) in some network drivers, the most commonly
used/available ones:
o  dc(4)
o  fxp(4)
o  vr(4)
There are actually more drivers that do not support busdma(9):
find /usr/src/sys/dev/netif -type f -name "*.c" -exec grep -l
"contigmalloc" "{}" ";"

I could help to review, test and commit the patch.

Best Regards,
sephe

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Tomorrow Will Never Die