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

From: Roger Gammans (
Date: Fri Aug 04 2000 - 09:05:55 EST

On Fri, Aug 04, 2000 at 02:18:52PM +0100, Alan Cox wrote:
> > I been asked to put togther some driver support for some of these cards
> > and was thinking about an ioctl, but is there a std which overs this?
> For a radio modem I got involved with the RS485 was just done in userspace
> via the modem control ioctls

There are different h/w arrangement for RS485 IIRC though, these cards give
the folowing options:-
        Half-duplex auto-gated,
        Half-duplex RTS switch, tx when RTS high[1]
        Half-duplex RTS switch, tx when RTS low[1]
        Both Tx/Rx Disabled.
         Tx only
        Rx Only
        Full Duplex.

I guess you were using either option 2 or 3 with that.

These various modes are handled by the hardware and you can switch
them just be setting the register approriately. Assuming kernel
or CAP_SYS_RAWIO (is this the right one?).


[1] Just to confuse matters one set of these cards then goes and uses DTR
    instead of RTS.

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

- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to Please read the FAQ at

This archive was generated by hypermail 2b29 : Mon Aug 07 2000 - 21:00:13 EST