嵌入式linux和uboot中关于读写寄存器的函数(__raw_writel, writel等)
uboot中是这么定义的：
u-boot_2.3.5/arch/arm/include/asm/io.h
/*
* Generic virtual read/write. Note that we don't support half-word
* read/writes. We define __arch_*[bl] here, and leave __arch_*w
* to the architecture specific code.
*/
#define __arch_getb(a) (*(volatile unsigned char *)(a))
#define __arch_getw(a) (*(volatile unsigned short *)(a))
#define __arch_getl(a) (*(volatile unsigned int *)(a)) //就是把值通过指针读出来
#define __arch_putb(v,a) (*(volatile unsigned char *)(a) = (v))
#define __arch_putw(v,a) (*(volatile unsigned short *)(a) = (v))
#define __arch_putl(v,a) (*(volatile unsigned int *)(a) = (v)) //写入v
#define __raw_writeb(v,a) __arch_putb(v,a)
#define __raw_writew(v,a) __arch_putw(v,a)
#define __raw_writel(v,a) __arch_putl(v,a)
#define __raw_readb(a) __arch_getb(a)
#define __raw_readw(a) __arch_getw(a)
#define __raw_readl(a) __arch_getl(a)
#define writeb(v,a) __arch_putb(v,a)
#define writew(v,a) __arch_putw(v,a)
#define writel(v,a) __arch_putl(v,a) //好像与“__raw_writel” 没有什么区别
#define readb(a) __arch_getb(a)
#define readw(a) __arch_getw(a)
#define readl(a) __arch_getl(a)