Want to write a single byte in the I/O address space (2C0) u

QNX Newsgroups (Archives) comp.os.qnx
1

I am writing an ISA card driver under QNX 4.25. The physical port I/O
address of the card is 2C0. How does one read and write a single byte at
physical address 2C0? Does this operation require x86 assembler?

Thanks in advance

2

I think inp()/outp() is what you are looking for.

“Douglas Reed” <dreed@guise.com> wrote in message
news:3BCCDE2A.B09DB140@guise.com…

I am writing an ISA card driver under QNX 4.25. The physical port I/O
address of the card is 2C0. How does one read and write a single byte at
physical address 2C0? Does this operation require x86 assembler?

Thanks in advance

3

Brown, Richard <brownr@aecl.ca> wrote:

I think inp()/outp() is what you are looking for.

Yup. And if a process is going to call inp()/outp(), then the process
must be linked with the -T1 flag (cc -T1 for the link) and must be run
as root. If a process makes use of inp()/outp() without the -T1 (set
privity) it will SIGSEGV when it tries to read/write the address.

-David

“Douglas Reed” <> dreed@guise.com> > wrote in message
news:> 3BCCDE2A.B09DB140@guise.com> …
I am writing an ISA card driver under QNX 4.25. The physical port I/O
address of the card is 2C0. How does one read and write a single byte at
physical address 2C0? Does this operation require x86 assembler?

Thanks in advance

–
QNX Training Services
dagibbs@qnx.com