devfs
Ian Molton
Robert Love <r...@tech9.net> wrote:
> On Mon, 2002-11-11 at 20:32, Ryan Anderson wrote:
>
> > From an outsider point of view (and because nobody else responded),
> > I think the big question here would be: Would you use it after this
> > cleanup?
> >
> > If you say yes, I'd say that's a good sign in its favor.
>
> Good heuristic, except Al would not use devfs in either case :)
Personally I love devfs. I've not looked at its internals, but its never
failed me yet, and I like the way /dev only contains stuff that actually
exists.
And if Al doesnt like the code... hes free to reimplement it...
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john slee
> I'm wondering if a totally userspace solution could replace devs ?
> Something using hotplug + sysfs and creating directories/nodes as they
> appear on the system. This way, the policy (how do I name what) could be
> moved out of the kernel.
curious! you mean similar to (and a logical extension of) the 'disks'
command in solaris? at least i think thats what its called...
j.
--
toyota power: http://indigoid.net/
Sean Neakums
> On Tue, Nov 12, 2002 at 10:43:41AM +0100, Xavier Bestel wrote:
>> I'm wondering if a totally userspace solution could replace devs ?
>> Something using hotplug + sysfs and creating directories/nodes as
>> they appear on the system. This way, the policy (how do I name
>> what) could be moved out of the kernel.
>
> curious! you mean similar to (and a logical extension of) the
> 'disks' command in solaris? at least i think thats what its
> called...
Except that a /sbin/hotplug er, "solution", would be dynamic. I had
always assumed in the back of my mind that such a solution would make
devfs go away some day, although I don't think I actually read about
it anywhere.
Actually, here's a question: are /sbin/hotplug upcalls serialized in
some fashion? I'd hate to online a thousand devices in my disk array
and have the machine forkbomb itself.
--
/ |
[|] Sean Neakums | Questions are a burden to others;
[|] <snea...@zork.net> | answers a prison for oneself.
\ |
Alexander Viro
On 12 Nov 2002, Xavier Bestel wrote:
> I'm wondering if a totally userspace solution could replace devs ?
> Something using hotplug + sysfs and creating directories/nodes as they
> appear on the system. This way, the policy (how do I name what) could be
> moved out of the kernel.
Guys, may I remind you that Oct 31 had been more than a week ago?
Devfs *is* a race-ridden pile of crap, but we are in a goddamn feature
freeze, so let's get real.
Interfaces can and should be cleaned up. Ditto for semantics of
registering/unregistering - that allows to make glue in drivers more
straightforward. Majestic flamewars about removing the thing completely/
moving it to userland/etc. are exercises in masturbation by that point.
Again, WE ARE IN FEATURE FREEZE.
Now, does somebody have technical comments on the proposed changes?
Ian Molton
Alexander Viro <vi...@math.psu.edu> wrote:
> Again, WE ARE IN FEATURE FREEZE.
>
> Now, does somebody have technical comments on the proposed
> changes?
And since when did feature freeze affect, as the guy said, *purely*
userspace implementations?
(can it be done with current hotplug/sysfs?)
Dave Jones
> > Again, WE ARE IN FEATURE FREEZE.
> userspace implementations?
Since it would a *feature* to move it out of kernel space.
To reiterate : _FEATURE_ _FREEZE_. Nothing[1] new[2]
should be going into mainline at this point.
We should now be in the stabilising period, where we don't require
testers to have to upgrade their userspace every fortnight.
Dave
[1] Rusty's modules rewrite and whatever else Linus queed up
seems to have exemption from this rule. Hopefully there
isn't too much of this stuff.
[2] Where 'new' can also mean 'bloody large reimplementation'
--
| Dave Jones. http://www.codemonkey.org.uk
| SuSE Labs
Ian Molton
Dave Jones <da...@codemonkey.org.uk> wrote:
> > And since when did feature freeze affect, as the guy said, *purely*
> > userspace implementations?
>
> Since it would a *feature* to move it out of kernel space.
> To reiterate : _FEATURE_ _FREEZE_. Nothing[1] new[2]
> should be going into mainline at this point.
nothing new WOULD be going in. nor would devfs need to move out - just
disable it. It *is* still an option, is it not?
> We should now be in the stabilising period, where we don't require
> testers to have to upgrade their userspace every fortnight.
its not a kernel issue anymore, if its totally in userspace, is it?
Rando Christensen
<da...@codemonkey.org.uk>):
> On Tue, Nov 12, 2002 at 10:25:35AM +0000, Ian Molton wrote:
> > > Again, WE ARE IN FEATURE FREEZE.
> > And since when did feature freeze affect, as the guy said, *purely*
> > userspace implementations?
> Since it would a *feature* to move it out of kernel space.
> To reiterate : _FEATURE_ _FREEZE_. Nothing[1] new[2]
> should be going into mainline at this point.
Well, it does make sense to start planning out what might be done to
devfs in the /next/ devel kernel, then. If one were so inclined, they
could have a stable enough system for it ready for inclusion next time
around, depending on who they get to test it.
Clean up the devfs API for now, and start working on what might
eventually replace it- Whether that's devfs2 or a purely userspace
implementation or something new and wacky is up to whoever writes it.
Rather than saying "Devfs sucks, and we can't do anything about it other
than fix it's more minor problems because we're in feature freeze", we
should be saying "devfs sucks; we're a little late for feature freeze,
so let's clean up what we can and work on something much better for the
next time around."
Devfs as it is now is a nice idea, to me. It's an extremely organized
/dev which is also an accurate portrayal of what's available to use on a
particular machine. I'd hate to see it just ripped out entirely, and
while they've never affected me, I've heard of many issues with it. I'd
like to hear what ideas people may have /for/ a future replacement.
--
< There is a light that shines on the frontier >
< And maybe someday, We're gonna be there. >
< Rando Christensen / ra...@babblica.net >
Helge Hafting
>
> On 12 Nov 2002, Xavier Bestel wrote:
>
> > I'm wondering if a totally userspace solution could replace devs ?
> > Something using hotplug + sysfs and creating directories/nodes as they
> > appear on the system. This way, the policy (how do I name what) could be
> > moved out of the kernel.
>
> Guys, may I remind you that Oct 31 had been more than a week ago?
> Devfs *is* a race-ridden pile of crap, but we are in a goddamn feature
> freeze, so let's get real.
>
so let him try. :-) It won't affect the current devfs code, it'll
simply be configured out.
/dev on tmpfs, populated by hotplug. Could be interesting to see.
[...]
> Now, does somebody have technical comments on the proposed changes?
Only the obvious - a cleanup is generally good and so is getting rid
of unused parameters.
Helge Hafting
Alexander Viro
On Tue, 12 Nov 2002, Rando Christensen wrote:
> Rather than saying "Devfs sucks, and we can't do anything about it other
> than fix it's more minor problems because we're in feature freeze", we
> should be saying "devfs sucks; we're a little late for feature freeze,
> so let's clean up what we can and work on something much better for the
> next time around."
Whatever is going to happen with devfs, believe me, the first thing
you'll need is stable glue in drivers - as simple and natural from the
driver POV as possible. Complexity of doing development in 2.6 will
directly depend on the amount of code in drivers touched by patches.
BTDT - one can carry (and gradually merge) deep rewrites of core code
during -STABLE if it's done carefully. But as soon as your patchset
hits the drivers - you are in for a world of pain just porting it to
next versions.
_That_ is critical - get interfaces right in -CURRENT, so that further
work would not cross these boundaries; then work in the resulting areas
becomes independent.
And in situations like that of devfs, simple rules for callers are pretty
much the main criteria - if users of the interface have to jump through
some hoops, it's a sign that interface needs changes...
Alan Cox
> On Tue, Nov 12, 2002 at 10:25:35AM +0000, Ian Molton wrote:
> > > Again, WE ARE IN FEATURE FREEZE.
> > And since when did feature freeze affect, as the guy said, *purely*
> > userspace implementations?
>
> Since it would a *feature* to move it out of kernel space.
> To reiterate : _FEATURE_ _FREEZE_. Nothing[1] new[2]
> should be going into mainline at this point.
Who cares. You can do most of it already with hotplug and the remaining
bits are very much "oops should tell hotplug" bug fixes nothing more.
Alan
Ian Molton
Alan Cox <al...@lxorguk.ukuu.org.uk> wrote:
> > Since it would a *feature* to move it out of kernel space.
> > To reiterate : _FEATURE_ _FREEZE_. Nothing[1] new[2]
> > should be going into mainline at this point.
>
> Who cares. You can do most of it already with hotplug and the
> remaining bits are very much "oops should tell hotplug" bug fixes
> nothing more.
The more I think about this userspace devfs, the more I like it. simple,
clean, AND doesnt affect the kernel.
Pure coding beauty.
Greg KH
>
> I'm wondering if a totally userspace solution could replace devs ?
> Something using hotplug + sysfs and creating directories/nodes as they
> appear on the system. This way, the policy (how do I name what) could be
> moved out of the kernel.
Yes, that is _exactly_ what I am working on doing, and have stated as
such on this list a number of times in the past.
As for it being after the feature freeze comment, like Alan noted,
everything is already present to do this, it's just going to take some
more notifiers being added and some userspace code written.
And no, even if all of this gets done, I would not want to remove devfs
from the kernel, yet :)
thanks,
greg k-h