嵌入式linux和uboot中关于读写寄存器的函数(__raw_writel, writel等)

最新推荐文章于 2024-08-12 23:00:00 发布

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#嵌入式 #linux

本文介绍了在U-Boot的arm架构中，用于读写寄存器的一系列函数，如__raw_writel、writeb等。这些函数在io.h头文件中被定义，提供了对内存地址进行字节、字和长整型读写的接口，对于理解和操作嵌入式系统的底层硬件具有重要意义。

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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)

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