linux　端口IO操作

linux对于端口IO使用遵循分配，映射与使用

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

申请失败返回NULL,否则非零。

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

释放。

void *ioremap(unsigned long phys_addr,unsigned long size);

void iounmap(void *addr);

映射与反操作。

unsigned int ioread8(void *addr);

unsigned int ioread16(void *addr);

unsigned int ioread32(void *addr);

void iowrite8(u8 value,void *addr);

void iowrite16(u16 value,void *addr);

void iowrite32(u32 value,void *addr);