Question

I was wondering if Linux sees a difference between mmap to a peripheral devices memory in comparision to reading/writing to the device via I/O Ports. From what I’ve learned in my Assembly class, we pretty much looked at I/O port addressing in the same light as memory addressing. So I suppose I was wondering if I were to rw to the I/O my port my device is connected to, is that the same thing mmaping to that devices memory?

Thanks

Answer 1

I/O ports are not memory. Some hardware (e.g. graphical cards) are interfaced thru the memory bus, not only thru the I/O port bus.

For hardware having a memory interface (that is, viewed as a range of memory to the CPU), you might use mmap.

The X11 server Xorg is very often mmap-ing the graphical cards.