Linux Device Drivers, Second Edition

Quick Reference

This chapter introduced the following symbols related to memory handling. The list doesn’t include the symbols introduced in the first section, as that section is a huge list in itself and those symbols are rarely useful to device drivers.

#include <linux/mm.h>

All the functions and structures related to memory management are prototyped and defined in this header.

int remap_page_range(unsigned long virt_add, unsigned long phys_add, unsigned long size, pgprot_t prot);

This function sits at the heart of mmap. It maps size bytes of physical addresses, starting at phys_addr, to the virtual address virt_add. The protection bits associated with the virtual space are specified in prot.

struct page *virt_to_page(void *kaddr); , void *page_address(struct page *page);

These macros convert between kernel logical addresses and their associated memory map entries. page_address only works for low-memory pages, or high-memory pages that have been explicitly mapped.

void *__va(unsigned long physaddr); , unsigned long __pa(void *kaddr);

These macros convert between kernel logical addresses and physical addresses.

unsigned long kmap(struct page *page); , void kunmap(struct page *page);

kmap returns a kernel virtual address that is mapped to the given page, creating the mapping if need be. kunmap deletes the mapping for the given page.

#include <linux/iobuf.h> , void kiobuf_init(struct kiobuf *iobuf); , int alloc_kiovec(int number, struct kiobuf **iobuf); ...