[Linux-parport] Checking for bidirectional support

Jason Curl j.m.curl at optusnet.com.au
Thu Jan 18 12:49:26 EST 2007

Jason Curl wrote:
> Hello,
> I've scrounged through the web, and I can't find a reliable way in my code to
> test if the ioctl(fd, PPDATADIR, &dir) will set the parallel port to read.

Replying to my own post, for completeness for other people like me, it's 
the TRISTATE flag.

My problems stemmed from using a PCMCIA card, it not working (only the 
feature PCSPP and not tristate).

> As far as I know, all my ports support ECP, etc. and I've configured them as
> such.
> I get PCSPP, TRISTATE, EPP in the kernel messages when ppdev starts (it's a
> loadable module). When I enable ECP from the BIOS, I get PCSPP, TRISTATE.
> I don't see anything obvious in ppdev.h or parport.h that indicates there is
> bidirectional support.
> Thanks in advance,
> Jason.

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