Mapping I/O memory in virtual memory

• Load/store instructions work with virtual addresses

• To access I/O memory, drivers need to have a virtual address that the processor can handle, because I/O memory is not mapped by default in virtual memory.

• The ioremap functions satisfy this need:

#include <asm/io.h>; void *ioremap(unsigned long phys_addr, unsigned long size); void iounmap(void *address);

• Caution: check that ioremap doesn't return a NULL address!