oper@mikrobitti.fi writes:

>>A friend of mine is trying to get a DigiBoard serial card working on
>>NetBSD.  He would like to peek the UART registers to see what is going
>>on with them.

>>Is it possible to use /dev/io to read (and write?) i386 IO space
>>registers?  If so, how?

Mike Long writes:

>First: AFAIK, use of /dev/io is discouraged; you should use the
>functions (e.g. ioperm()) in libi386.a instead.

>/dev/io is similar to /dev/mem, except that it accesses the x86 I/O
>space instead of memory.  To use /dev/io, use something like:

<	[ using lseek() to seek within /dev/io ]

	Actually, the way I had understood it was that if you merely open()
/dev/io, then your process was then allowed to use the assembly-level 
inb() and outb() macros located in /usr/include/machine/pio.h.

	The way that is preferred now is to use i386_get_ioperm() and
i386_set_ioperm() to twiddle bits in a bitmap to allow you to access 
specific ports; and _then_ use the inb() and outb() macros in machine/pio.h.

	Using the assembler macros is undoubtedly much faster than
doing read's and write's to /dev/io ..

Cheers,
Phil
--
Phillip F Knaack               flipk@iastate.edu
Database Programmer, NCREMP    Student Development Group
ISU Extension                  Project Vincent, Iowa State University