Subject: Re: TTY virtualization driver
To: NetBSD Kernel Technical Discussion List <tech-kern@NetBSD.ORG>
From: Bill Studenmund <email@example.com>
Date: 01/24/2002 16:05:03
On Thu, 24 Jan 2002, Greg A. Woods wrote:
> [ On Thursday, January 24, 2002 at 13:31:40 (-0800), Jason R Thorpe wrote: ]
> > Subject: Re: TTY virtualization driver
> > So, the idea of having a virtualized TTY layer is nice, but there are
> > some real problems with it, the biggest one being naming.
> So goes it with /dev/sd* too.... :-)
Not quite. While it's a similar issue, differences in how systems usually
are set up make (IMHO) sd's attaching wherever make more sense than having
tty's attach wherever (the "virtual" layer).
One big difference is that when you have a tty, you really have a plug you
can hook something into, whereas when you have a disk (sd or wd) you have
a disk plugged into a controller and configured to appear at a specific
address. For ttys, the drivers don't know if there's something out there,
just that there's a plug.
So when you plug in a serial controller with 16 ports, you have 16 tty
ports. But when you plug in a wide scsi controller (which can support 16
targets), you don't necessarily have 15 other drives out there. You can
have tape drives, scanners, and ethernet devices at these targets too,
*AND* the scsi controller can tell what they are. So we know what's there.
That's a big difference. So it make sense (to me) that how we handle sd*
devices is different (and IMHO should stay different) from how we handle