Linux Device Drivers, Second Edition

Quick Reference

This chapter introduced the following symbols related to hardware management.

#include <linux/kernel.h> , void barrier(void)

This “software” memory barrier requests the compiler to consider all memory volatile across this instruction.

#include <asm/system.h> , void rmb(void); , void wmb(void); , void mb(void);

Hardware memory barriers. They request the CPU (and the compiler) to checkpoint all memory reads, writes, or both, across this instruction.

#include <asm/io.h> , unsigned inb(unsigned port); , void outb(unsigned char byte, unsigned port); , unsigned inw(unsigned port); , void outw(unsigned short word, unsigned port); , unsigned inl(unsigned port); , void outl(unsigned doubleword, unsigned port);

These functions are used to read and write I/O ports. They can also be called by user-space programs, provided they have the right privileges to access ports.

unsigned inb_p(unsigned port); , ...

The statement SLOW_DOWN_IO is sometimes needed to deal with slow ISA boards on the x86 platform. If a small delay is needed after an I/O operation, you can use the six pausing counterparts of the functions introduced in the previous entry; these pausing functions have names ending in _p.

void insb(unsigned port, void *addr, unsigned long count); , void outsb(unsigned port, void *addr, unsigned long count); , void insw(unsigned port, void *addr, unsigned long count); , void outsw(unsigned port, void *addr, unsigned long count); , ...