Re: devfs vs udev/hotplug

[Hiten Pandya <hmp@xxxxxxxxxxxxx>]

Dave Leimbach wrote:

> Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx> writes:
>
>
> > : (Simon)
> > :> What do people think of the udev/hotplug solution vs devfs? At first 
> > :> inspection, udev appears to be a little more Dragonfly-ish because of 
> > :> its placement in userland.
> > :
> > :I'd vote for udev (or something like it)
> > :
> > :-- 
> >
> >    I think I would prefer udev over devfs.  It seems silly to try to manage
> >    yet another fake filesystem in the kernel, just look at all the bugs 
> >    that have cropped up in existing devfs and procfs implementations, not
> >    to mention unionfs and nullfs!  You'd think we would have learned our
> >    lesson by now!
> >
> >    I would definitely prefer a userland demon which performs the work based
> >    on what the kernels tells it to do.  The kernel can still assign dynamic
> >    minor numbers for dynamic devices, and that is really the crux of the
> >    functionality we want to have.
>
>
> Doesn't this sort of design imply that the kernel is instructing a daemon
> to make kernel calls to service the requests?  Isn't that a lot of 
> address space crossing or do I not understand how a userland file "server"
> would work?  I realize that this will be done with fast messages but such
> designs leave me with "speed" doubts.  This might be a bad example for when
> that speed matters though.
>
> Dave

	I don't think speed will be much of an issue, once Async
	messaging and a Shared Memory Segment between userland and
	kernel is implemented.  One can utilize that.

	Regards,

		-Hiten
		Hiten Pandya
		hmp@xxxxxxxxxxxxx