第九章 与硬件通信

 

1.概念：

I/O 端口：设备通常提供的控制寄存器、数据寄存器、状态寄存器，当它们位于I/O空间时。通过特定的指令来访问

I/O 内存：设备通常提供的控制寄存器、数据寄存器、状态寄存器，当它们位于内存空间时。

 

在硬件级别上, I/O内存区和 I/O 区域没有概念上的区别: 它们都是通过在地址总线和控制总线上发出电信号来存取(即, 读写信号)，并且读自或者写到数据总线.

 

大部分嵌入式，微处理器不提供I/O空间，即没有I/O端口。

 

2 I/O 端口使用：

方法1：直接用特定指令访问

#include
struct resource *request_region(unsigned long first, unsigned long n, const char *name);

void release_region(unsigned long start, unsigned long n);

int check_region(unsigned long first, unsigned long n);

 

方法2：将I/O端口转化为I/O内存来访问

 

 

void *ioport_map(unsigned long port, unsigned int count);
void ioport_unmap(void *addr);

3 I/O 内存使用

 

struct resource *request_mem_region(unsigned long start, unsigned long len, char *name);

void release_mem_region(unsigned long start, unsigned long len);

int check_mem_region(unsigned long start, unsigned long len);

 

#include
void *ioremap(unsigned long phys_addr, unsigned long size);
void *ioremap_nocache(unsigned long phys_addr, unsigned long size);
void iounmap(void * addr);

 

4 I/O端口读写函数

     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 longword, unsigned port);

字串函数的原型是:

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);

void insl(unsigned port, void *addr, unsigned long count);

void outsl(unsigned port, void *addr, unsigned long count);

5 I/O内存读写函数

读字节

unsigned int ioread8(void *addr);
unsigned int ioread16(void *addr);
unsigned int ioread32(void *addr);

对应的较早版本函数为（2.6仍支持）

unsigned readb(address);
unsigned readw(address);
unsigned readl(address);

写字节

void iowrite8(u8 value, void *addr);
void iowrite16(u16 value, void *addr);
void iowrite32(u32 value, void *addr);
对应的较早版本函数为（2.6仍支持）

void writeb(unsigned value, address);
void writew(unsigned value, address);
void writel(unsigned value, address);

 

读一串

void ioread8_rep(void *addr, void *buf, unsigned long count);
void ioread16_rep(void *addr, void *buf, unsigned long count);

void ioread32_rep(void *addr, void *buf, unsigned long count);

写一串

void iowrite8_rep(void *addr, const void *buf, unsigned long count);
void iowrite16_rep(void *addr, const void *buf, unsigned long count);
void iowrite32_rep(void *addr, const void *buf, unsigned long count);

复制I/O

void memcpy_fromio(void *dest, void *source, unsigned int count);
void memcpy_toio(void *dest, void *source, unsigned int count);

设置I/O

void memset_io(void *addr, u8 value, unsigned int count);