Re: HEAD UP: non-MPSAFE network drivers to be disabled

Poul-Henning Kamp wrote:
> In message <20080526161608.GE64397_at_hoeg.nl>, Ed Schouten writes:
> 
>> The new TTY layer should still support line disciplines, [...]
> 
> Actually...  I think it shouldn't.
> 
> Line-disc's were introduced to interface weird-ass hardware like
> digitizing tablets that had very high data rates, but very little
> information (16 bit X, 16 bit Y and a couple of buttons, like modern
> mice) which would cost inordinate amounts of CPU time to support
> in userland on a VAX computer.
> 
> If_slip.c happened in the kernel because there was no tun device,
> people cranked the speed up all they could (Hands up: who has changed
> the Xtal on a VAX serial port for faster SLIP ?)
> 
> if_ppp happened because that was how if_slip did it.
> 
> Today there is no longer a market for line disciplines and in
> practice we have only one: the POSIX mandated "termios", which also
> emulates the older "termio" ioctls.
> 
> Anybody who cares to browse the three pages of text that RFC1055
> contains, will see that implementing SLIP in userland using tun(4)
> and the code on the other three pages of RFC1055 is a trivial task
> not even worthy of a SoC student.
> 
> PPP over async is already much better handled in ppp(8) thanks
> to Brians valiant effort back in the stoneage of the internet.
> 
> We should summarily kill the concept of line disciplines as a
> modular component and decide that TTYs can be used with termios(4)
> or raw mode and leave it at that.
> 
> Poul-Henning
> 


However the line discipline was a very convenient place for netgraph 
to hook in without leaving the kernel. If you can supply an equally
effective way to hook into a serial device in such a way that it 
appears to be a source/sink of bits then I don't care about
line disciplins, but until you have a suggested replacement then leave 
them alone. There are MANY people using mpd with the netgraph ppp 
moduel hooked directly to the serial port via the netgraph line 
discipline.