Linux内核中IO地址空间映射实例
关于IO地址映射，如中断外设的地址和映射后的地址访问下面是P1020 手册中关于PIC中断控制器的描述PIC Memory Map/Register DefinitionThe PIC programmable register map occupies 256 Kbytes of memory-mapped space.Reading undefined portions
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关于IO地址映射，如中断外设的地址和映射后的地址访问
下面是P1020 手册中关于PIC中断控制器的描述
PIC Memory Map/Register Definition
The PIC programmable register map occupies 256 Kbytes of memory-mapped space.
Reading undefined portions of the memory map returns all zeros; writing has no effect.All PIC registers are 32 bits wide and, although located on 128-bit address boundaries,
should be accessed only as 32-bit quantities.
The PIC address offset map is divided into three areas:
• 0xnn4_0000-0xnn4_FFF0-Global registers
• 0xnn5_0000-0xnn5_FFF0-Interrupt source configuration registers
• 0xnn6_0000-0xnn7_FFF0-Per-CPU registers
由图看到，假如我想访问PIC_EIVPR4，程序如下
int16->pic_vaddr =(unsigned int *)ioremap(get_immrbase() + 0x50080, 128); 如果我想访问PIC_EIDR4
out_be32((int16->pic_vaddr+4), regdata);注意PIC控制器的描述：
All PIC registers are 32 bits wide and, although located on 128-bit address boundaries,
should be accessed only as 32-bit quantities.
实际上PIC寄存器是32位宽，但占用了128bit（16个int）地址范围
但访问还是要按照32位的地址
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