devmem2的方式是提供给驱动开发人员，在应用层能够侦测内存地址中的数据变化，以此来检测驱动中对内存或者相关配置的正确性验证。基本原理通过设备文件/dev/mem 实现对物理内存的读写,如果没有dev/mem,这时需要安装devmem2。

1,安装devmem2:

sudo apt install devmem2

lark@ubuntu:~$ devmem2 

Usage:    devmem2 { address } [ type [ data ] ]
 address : memory address to act upon
type    : access operation type : [b]yte, [h]alfword, [w]ord
data    : data to be written

安装成功后会有/dev/mem 这个目录。

lark@ubuntu:~$ ls /dev/mem 
/dev/mem

2，读写测试

a，读数据：

devmem2 reg-addr b/h/w(1/2/4) 

b，写数据：

devmem2 reg-addr b/h/w(1/2/value

（1）单字节读写（8位）：

lark@ubuntu:~$ sudo devmem2 0x1234 b 0x11
/dev/mem opened.
Memory mapped at address 0x7f659293d000.
Value at address 0x1234 (0x7f659293d234): 0x78
Written 0x11; readback 0x11

lark@ubuntu:~$ sudo devmem2 0x1234 b 
/dev/mem opened.
Memory mapped at address 0x7fd47bed1000.
Value at address 0x1234 (0x7fd47bed1234): 0x11

（2）双字节读写（16位）：

lark@ubuntu:~$ sudo devmem2 0x1234 b 
/dev/mem opened.
Memory mapped at address 0x7fd47bed1000.
Value at address 0x1234 (0x7fd47bed1234): 0x11
lark@ubuntu:~$ sudo devmem2 0x1234 h 0x1122
/dev/mem opened.
Memory mapped at address 0x7f218fb9b000.
Value at address 0x1234 (0x7f218fb9b234): 0x5611
Written 0x1122; readback 0x1122

lark@ubuntu:~$ sudo devmem2 0x1234 h
/dev/mem opened.
Memory mapped at address 0x7feaa9be3000.
Value at address 0x1234 (0x7feaa9be3234): 0x1122
 

（3）四字节速写（四字节）：

lark@ubuntu:~$ sudo devmem2 0x1234 w 0x12345678
/dev/mem opened.
Memory mapped at address 0x7f2d21327000.
Value at address 0x1234 (0x7f2d21327234): 0xBC614E
Written 0x12345678; readback 0x12345678

lark@ubuntu:~$ sudo devmem2 0x1234 w
/dev/mem opened.
Memory mapped at address 0x7f31ad806000.
Value at address 0x1234 (0x7f31ad806234): 0x12345678

lark@ubuntu:~$ sudo devmem2 0x1234 h
/dev/mem opened.
Memory mapped at address 0x7fd131870000.
Value at address 0x1234 (0x7fd131870234): 0x5678

lark@ubuntu:~$ sudo devmem2 0x1234 b
/dev/mem opened.
Memory mapped at address 0x7f2fe1866000.
Value at address 0x1234 (0x7f2fe1866234): 0x78