Linux Device Drivers Development

Using io_remap_pfn_range

The remap_pfn_range() function discussed does not apply anymore when it comes to mapping I/O memory to user space. In this case, the appropriate function is io_remap_pfn_range(), whose parameters are the same. The only thing that changes is where the PFN comes from. Its prototype looks like:

int io_remap_page_range(struct vm_area_struct *vma, 
                        unsigned long virt_addr, 
                        unsigned long phys_addr, 
                        unsigned long size, pgprot_t prot); 

There is no need to use ioremap() when attempting to map I/O memory to user space. ioremap() is intended for kernel purposes (mapping I/O memory into the kernel address space), whereas io_remap_pfn_range is for user space purposes.

Just pass your real physical I/O address (downshifted by