arch/arm/include/asm/io.h

#define __raw_writeb(v,a)    (__chk_io_ptr(a), *(volatile unsigned char __force  *)(a) = (v))
#define __raw_writew(v,a)    (__chk_io_ptr(a), *(volatile unsigned short __force *)(a) = (v))
#define __raw_writel(v,a)    (__chk_io_ptr(a), *(volatile unsigned int __force   *)(a) = (v))

#define __raw_readb(a)        (__chk_io_ptr(a), *(volatile unsigned char __force  *)(a))
#define __raw_readw(a)        (__chk_io_ptr(a), *(volatile unsigned short __force *)(a))

#define __raw_readl(a)        (__chk_io_ptr(a), *(volatile unsigned int __force   *)(a))

//for arm32

char 1byte

shot 2bytes

int 4bytes