[PATCH] Documentation about RS485 serial communications

[Alan Cox]

> Comtrol, Moxa, B&B, Sealevel, and others all sell PCI cards and
> Ethernet attached serial ports that have selectable interfaces
> (typically RS-232/422/485).  Comtrol and Moxa have had drivers in the
> kernel tree for ages, but they've always had to use custom ioctl calls
> for things like configuring 232/485/422 mode and half/full-duplex
> mode.

Ok so what is needed that isn't covered by the current termiox and
TIOCG/SRS485 ioctls ?

> Having a standard API for things like interface mode, half-full
> duplex, inter-character timeout, 9-bit mode, and so on would be life a
> lot easier for those of us who maintain Linux serial drivers...

9bit mode is a real problem with the tty layer defined in terms of 8bit
streams but yes.