Re: Re hardware handshake support for 2.0/2.2/2.4

[Roger Gammans]

On Tue, Aug 08, 2000 at 01:16:41PM -0400, Theodore Ts'o wrote:
> The problem with half-duplex support is that *everyone* seems to do it
> different.  Some use RTS high, some use RTS low, some use DSR/DTR/CD,
>[snip]
> So as a result, my bias has been to leave out any kind of half-duplex
> support, since there's no standard, and so trading off the limited

For 2.5 there is Stuart MacDonald's TIOCRS485GET/SET patch that I gather 
he'll be sending later.

This uses a per-card control function which would be needed anyway,
the problem is support for additional magic outside the UART.

This patch could be extended to _define_ all the various options and leave
it up to user space what is chosen, if the card doesn't support that
option it can the return -EINVAL or some such.

It wouldn't be much bloat to add #defines for the other options, the way 
he has done it, except in the card support stage, and that only affect
card which support the option.

>I'm willing to be convinced, if someone can come up with some official
>RS-232 standard indicating this *is* how you support half-duplex, and

Well, its 485/422 anyway , but ISTR there a a number of industrial
buses based around these but they are all different, all standards still,
some have official (for some values of) blessing in their industrial sector.

TTFN
-- 
Roger
     Think of the mess on the carpet. Sensible people do all their
     demon-summoning in the garage, which you can just hose down afterwards.
        --     [e-mail]