On Wednesday 22 July 2009 3:31:54 pm Alexander Best wrote:
> the ppi manual states that using ioctl with /dev/ppi is extremely slow. i need
> the parallel port to be really fast. i need to communicate with a device that
> uses asynchronous transfer at a rate of ~ 2 mhz. so i need the full ISA bus
> speed to be able to push/pull data to/from the parallel port without any
> delays. timing is really critical. if there's a lot of work to do for the
> scheduler and the io calls get queued too long the transfer will fail.
The overhead of ppi is probably in the noise on a modern CPU. I think you
should be fine with just using ppi(4).
> actually i meant: how can i check the available parallel ports from within my
> app? is there a syscall i can use or something like that?
You can look for ppcX devices perhaps. The easiest way might be to enable
ppi and look for /dev/ppiX devices in /dev.
--
John Baldwin