[Gumstix-users] Writing directly to serial ports

[Stephan Gn. <gue...@in...>]

Hello,
I've written a TTY Driver which creates a number of logical character
devices. User space programs should be able to communicate with these
logical devices as with any other character device. The task of the TTY
driver is:
1) Parse the input
2) Determine to which device the user has written to
3) Determine if the input is valid
4) Format data
5) Send it out of the physical serial port (I/O 0x3f8 e.g.)

I'm using outb() and in(b) for communication with the hardware. This works
fine on my x86 development system. But when I load the module on my gumstix,
the try to write to the I/O adress results in a segmentation fault.

I googled a bit and found out, that the Gumstix are using something called
GPIO. The principle is clear - a bunch of processor pins which can be
configured for input or output and so on.
But how can I directly access the hardware? Are the GPIOs mapped to a kind
of I/O address? Do the macros inb() and outb() work on ARM architecture at
all? Are the alternative macros for use with GPIO?


Thanks a lot!