Re: Review/Test: Pseudo-device unit number management patch

On Fri, 6 Feb 2004, Poul-Henning Kamp wrote:

> 
> http://phk.freebsd.dk/patch/pseudo.patch
> 
> This patch adds a couple of functions for pseudodrivers to use for
> implementing cloning in a manner we will be able to lock down
> (shortly).
> 
> Basically what happens is that pseudo drivers get a way to ask for
> "give me the dev_t with this unit number" or alternatively "give
> me a dev_t with the lowest guaranteed free unit number" (there are
> a lot of non-POLA in the value of this number, just live with it
> for now!)
> 
> Managing the unit number space this way removes the need to use
> rman(9) and greatly simplifies the code in the drivers because
> even using rman(9) they still needed to manage their dev_t's too.
> 
> I have taken the if_tun, if_tap and nmdm drivers through the mill,
> partly because they (ab)used makedev(), but mostly because together
> they represent three different problems for device-cloning:
> 
> 	if_tun is the plain case: just give me a device.
> 	if_tap has two kinds of devices, with a flag for device type.
> 	nmdm has paired devices (a'la pty).
> 
> I would appreciate if people would test these devices work _as
> previously_ with this patch in place.

well that depends on your definition of "as previously"

Previously, nmdm started off with 4 devices visible in /dev now I don't
see that.. The old behaviour was intuitive... You saw a device. You
openned it and used it, and as you used them extra ones would appear so
that there were always a few free. You could select the port to use in a
pulldown browser. Now you have to open an invisible device you can't
see.. doesn't seem so intuitive right now..

> 
> If nothing crops up, I plan to commit this patch in two weeks time.
> 
> Poul-Henning
> 
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk_at_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.
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