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Re: userspace drivers

From: Robert Millan
Subject: Re: userspace drivers
Date: Mon, 3 Feb 2003 14:28:52 +0100
User-agent: Mutt/1.5.3i

On Fri, Jan 31, 2003 at 09:08:40PM +0100, Marcus Brinkmann wrote:
> On Fri, Jan 31, 2003 at 04:36:35PM +0100, Robert Millan wrote:
> > I've read the IO section and doesn't realy seem a useful interface. any 
> > plans
> > to provide ioperm ()?
> ioperm is supported in GNU Mach v2, that's what I implemented a year ago

I tried on GNUMach 2 and it failed with errno "Function not implemented"..

> (and I think it is in the GNU Mach manual, although I am not sure).

ok, will take a look later

> GNU Mach v1 pathetically doesn't restrict I/O access at all (we could easily
> revert that to prevent all I/O access, though).

uhm please don't. without a working ioperm there's no way at all to access
I/O ports (other than the weird native interface in mach).

> The question of user interrupt handlers: There is an interface, but I don't
> think it was ever tried in GNU Mach, so I don't know if that works or can be
> resurrected.

well i think interrupts can wait. do you have a reference anyway?

> In any case user space drivers are only interesting in a more
> modern microkernel like L4.

they still have the typical advantages of coding in userspace, and
it's good to have them already so the L4 hackers can spend their time
on something else, so we have mature drivers by the time the Hurd is
ready for L4, etc.

particularly, i wanted to add a feature to the cdrom driver but i
prefer writing a userspace driver from scratch rather than learning mach

Robert Millan

"Omnis enim res, quad dando non deficit, dum habetur et non datur,
nondum habetur, quomodo habenda est."

"For if a thing is not diminished by being shared with others, it is
not rightly owned if it is only owned and not shared." 

                Aurelius Augustinus (354-430)

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