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SubjectRe: TTY changes to 2.1.65
Date
> Most of the time, people who are interested in using synchronous device
> drivers are interested in using these devices for networking
> applications --- i.e., X.25, Frame Relay, ISDN, etc. In those cases,
> you usually want to interface the synchronous device directly into the
> networking layer. There are in fact several synchoronous devices in the
> kernel which are done in exactly this way, and so it doesn't touch the
> tty code at all.

They often need too. The classic example is the Sparc, Mac, and PPC serial
ports. These interfaces support synchronous mode on a byte level needing
a very tty like interface

> line discipline could inform the low-level device driver what the
> "framing character" is, and this information would be used to determine

No framing character. Think instead

ioctl(tty_fd, TIOCSSYNC, &sync_defs);
v=TTY_LDISC_SYNCX25;
ioctl(tty_fd, TIOCLDISC, &v);
ioctl(tty_fd, SIOCGIFNAME, buf);

> stated above, synchronous devices will probably be always directly wired
> into the networking stack.

Not the low speed stuff. The tty layer is exactly what they need. I think
the framing is easy to handle too - just declare three of the error flags
for frame end, abort, and checksum byte (for the hardware computed HDLC
checksums off most chips).

Alan


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