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 -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk_at_FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.Received on Mon May 26 2008 - 17:11:20 UTC
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