按键按下用万用表测出电平变化， 但是查看对应GPIO的value文件却没有变化

[jianwei]

/sys/class/gpio # echo 37 > export 
/sys/class/gpio # cd gpio37 
/sys/devices/platform/soc@3000000/2000000.pinctrl/gpiochip0/gpio/gpio37 # cat direction 
in
/sys/devices/platform/soc@3000000/2000000.pinctrl/gpiochip0/gpio/gpio37 # cat active_low 
0
/sys/devices/platform/soc@3000000/2000000.pinctrl/gpiochip0/gpio/gpio37 # cat value 
0
/sys/devices/platform/soc@3000000/2000000.pinctrl/gpiochip0/gpio/gpio37 # cat value 
0
/sys/devices/platform/soc@3000000/2000000.pinctrl/gpiochip0/gpio/gpio37 # cat value 
0
/sys/devices/platform/soc@3000000/2000000.pinctrl/gpiochip0/gpio/gpio37 # 

按键对应的GPIO 是 PB5

请问需要怎么用程序检测按键状态变化呢？

[WhycanService]

按键可以用Linux内置的驱动gpio-keys，提供轮训中断等多种查询方式，而且直接对接了linux的event系统开发也很简单