Linux Device Drivers

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.

#include <asm/io.h> , unsigned long virt_to_bus(volatile void * address); , void * bus_to_virt(unsigned long address); , unsigned long virt_to_phys(volatile void * address); , void * phys_to_virt(unsigned long address);

These functions convert between virtual and physical addresses. Bus addresses must be used to talk to peripheral devices, phys addresses to talk to MMU circuits.

/proc/dma

This file contains a textual snapshot of the allocated channels in the DMA controllers. PCI-based DMA is not shown, as each board works independently, without the need to allocate a channel in the DMA controller.

#include <asm/dma.h>

This header defines or prototypes all the functions and macros related to DMA. It must be included ...