Unix Programming - Writing to i/o at a lower level

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Author Writing to i/o at a lower level
Andrew Falanga

2004-01-23, 5:02 pm

Hello,

Sorry for the earlier posting. I was able to get some help from a
knowledgable person here. I wasn't setting my file to setuid, and I
didn't have it owned by root. That problem is now taken care of.

I'm wondering now about writing data to an I/O port, but at a lower
level than say, cat <somefile> > /dev/parallel. I'm writing a C
program to write to the parallel/serial devices at this level. The
Linux HOWTO I referenced earlier (in earlier posting) specifies using
ioperm()/iopl() to gain access to the io device, and then using
outb()/inb() macros for character io.

I'm using these things as spelled out in the HOWTO, but nothing
appears to be happening. What are some things to look for?

Thanks,
Andy
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