HEADSUP: Change of makedev() semantics on FreeBSD

Freebird

FreeBSD's Poul-Henning Kamp is in the process of adding ref-counting and locking to dev_t, and would very much prefer if this step is completed soon before 5-STABLE gets branched. He says that all this will be transparent to the majority of device drivers, as the refcounting will happen in the make_dev() and destroy_dev() family of calls and normal drivers need not know more about it.

[Read email]
-------------------------------------
To: arch@freebsd.org, current@freebsd.org
From: Poul-Henning Kamp <phk@phk.freebsd.dk>
Date: Sun, 28 Sep 2003 23:22:07 +0200
Subject: HEADSUP: Change of makedev() semantics.

I am in the process of adding ref-counting and locking to dev_t,
and would very much prefer if we could get this step completed
soon before 5-STABLE gets branched.

All this will be transparent to the majority of device drivers, as
the refcounting will happen in the make_dev() and destroy_dev()
family of calls and normal drivers need not know more about it.

But there are a few remaining users of makedev() which get in the
way of this effort, and we must get these fixed.

Basically:

1. Do not call makedev().

2. If you do cloning, please look at the patches I posted
for if_tun/if_tap for how to do it.

3. If you do a "normal" device driver, cache the result
from when you call make_dev().

4. If you translate "foreign dev_t's", ie emulators or
compat code, contact me. I'm not sure I understand
how this works and should work and we need to talk.

5. If anything else or in doubt, ask me.

Can I see some volounteers and/or maintainers please ?

./alpha/osf1/osf1_misc.c
badly named local macro ?

./compat/linux/linux_stats.c
./compat/svr4/svr4_types.h
compat code, not sure that this is correct now.
Must be supported by new "finddev" semantics.

./dev/ata/atapi-cd.c
cloning related to root mount.
gets fixed when phk GEOMify the driver.

./dev/sound/midi/midi.h
Not sure.

./dev/nmdm/nmdm.c
pseudo-cloning. Should do real cloning.

./dev/syscons/syscons.c
Related to console initialization. Maybe tricky.

./dev/sound/pcm/dsp.c
./dev/sound/pcm/mixer.c
./dev/usb/ugen.c
./dev/usb/uscanner.c
Failure to cache result of make_dev()

./dev/vinum
Failure to cache result of make_dev() ?

Thanks in advance!

--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.