Re: Opencomm: proplib-based syscall

[Thor Lancelot Simon <tls%rek.tjls.com@localhost>]

On Sun, Apr 26, 2009 at 12:10:51PM +0100, Iain Hibbert wrote:
> On Sun, 26 Apr 2009, Antti Kantee wrote:
> 
> > I'm still not convinced.  Actually, I'm less convinced now.  To me,
> > your current argumentation pretty much reads: "add a generic interface
> > which can be used for something".  Implement a useful use case and then
> > you have something concrete to shut me up with.
> 
> The /dev/drvctl node could use this instead of needing a filesystem hook -
> as far as I recall it is an ioctl-only node that passes plists, nothing
> performance critical. Ditto for /dev/bthub which could be merged and I'm
> sure there are others I don't know about.

Why is this desirable?  I cannot see going the plan9 way and making the
filesystem namespace and permissions the _only_ kernel-user namespace and
permissions -- but I also see little or no point to discarding existing
uses of the filesystem namespace where they are convenient and simple.

We have ioctl-only device nodes in a number of places where older Unices
(including older NetBSD) had special-purpose system calls.  They offer
some very useful advantages, like reference (and per-user state) tracking
via the generic file and file descriptor handling code in the kernel, and
the ability to simply use chown and chmod for access control.

What advantage is there to undoing this and using special-purpose
syscalls all over the place, whether those syscalls' arguments are passed
as XML or something else?

Thor