WRTnode 2Q 按键驱动说明

咨询了一下WRTnode开发的相关人员,以及参考网上资料,大致搞明白OpenWrt系统下的按键驱动是怎么回事。
涉及文件:
   1、编译模块的文件
   build_dir/target-mips_34kc_uClibc-0.9.33.2/Linux-ar71xx_generic/linux-3.18.29/arch/mips/ath79/mach-wrtnode2q.c
   kernel/button-hotplug/src/button-hotplug.c

在mach-wrtnode2q.c中改变GPIO号,就可以将我们想要的GPIO注册为按键

#define WRTNODE2Q_GPIO_BTN_WPS      4

 static struct gpio_keys_button wrtnode2q_gpio_keys[] __initdata = {
     {
          .desc       = "WPS button",
          .type       = EV_KEY,
          .code       = KEY_WPS_BUTTON,
          .debounce_interval = WRTNODE2Q_KEYS_DEBOUNCE_INTERVAL,
          .gpio       = WRTNODE2Q_GPIO_BTN_WPS, //可改为需要注册的GPIO引脚
          .active_low = 1,
     },
  };

关键项说明:
   .type = EV_KEY  表示是一个 按键事件(linux  input系统中持的数据类型中的一种)
   .code = KEY_WPS_BUTTON  与 button-hotplug.c 中的button_map[]对应,具体如下

  static struct bh_map button_map[] = { 
      BH_MAP(BTN_0,       "BTN_0"),
      BH_MAP(BTN_1,       "BTN_1"),
      BH_MAP(BTN_2,       "BTN_2"),
      BH_MAP(BTN_3,       "BTN_3"),
      BH_MAP(BTN_4,       "BTN_4"),
      BH_MAP(BTN_5,       "BTN_5"),
      BH_MAP(BTN_6,       "BTN_6"),
      BH_MAP(BTN_7,       "BTN_7"),
      BH_MAP(BTN_8,       "BTN_8"),
      BH_MAP(BTN_9,       "BTN_9"),
      BH_MAP(KEY_RESTART, "reset"),
      BH_MAP(KEY_POWER,   "power"),
      BH_MAP(KEY_RFKILL,  "rfkill"),
      BH_MAP(KEY_WPS_BUTTON,  "wps"),
      BH_MAP(KEY_WIMAX,   "wwan"),
  };

reset、rfkill、power 对应于WRTnode2Q中/etc/rc.button/的脚本,下文具体解释。

然后调用ath79_register_gpio_keys_polled,关联到platform函数注册按键

 ath79_register_gpio_keys_polled(-1, WRTNODE2Q_KEYS_POLL_INTERVAL,
               ARRAY_SIZE(wrtnode2q_gpio_keys),
               wrtnode2q_gpio_keys);

WRTnode2Q涉及的程序及文件:
   /etc/hotplug.json
   /etc/rc.button/*

当按键时,则触发驱动中button_hotplug_event函数(button-hotplug.c   ):调用button_hotplug_create_event产生uevent事件,调用button_hotplug_fill_even填充事件(JSON格式),并最终调用button_hotplug_work发出uevent广播
上述广播,被procd进程中的hotplug_handler (procd/plug/hotplug.c) 收到,并根据etc/hotplug.json中预先定义的JSON内容匹配条件,定位到对应的执行函数,具体为:

[                                                                         
        [ "case", "ACTION", {                                                                      
                "add": [                                                            
                        [ "if",                                                                 
                                [ "and",                                            
                                        [ "has", "MAJOR" ],
                                        [ "has", "MINOR" ],                                     
                                ],                                                                 
                                [                                                               
                                        [ "if",                                                    
                                                [ "or",                                
                                                        [ "eq", "DEVNAME",   
                                                                [ "null", "full", "ptmx", "zero" ],
                                                        ],                                      
                                                        [ "regex", "DEVNAME",                   
                                                                [ "^gpio", "^hvc" ],   
                                                        ],                                      
                                                ],                   
                                                [                                               
                                                        [ "makedev", "/dev/%DEVNAME%", "0666" ],
                                                        [ "return" ],                         
                                                ]                                      
                                        ],                                                    
                                        [ "if",                                        
                                                [ "or",                                         
                                                        [ "eq", "DEVNAME", "mapper/control" ],
                                                        [ "regex", "DEVPATH", "^ppp" ],         
                                                ],                           
                                                [   
                                                        [ "makedev", "/dev/%DEVNAME%", "0600" ],
                                                        [ "return" ],                   
                                                ],                                      
                                        ],                                              
                                        [ "if",     
                                                [ "has", "DEVNAME" ],
                                                [ "makedev", "/dev/%DEVNAME%", "0644" ],
                                        ],                 
                                ],                                                      
                        ],                                                   
                        [ "if",                                                         
                                [ "has", "FIRMWARE" ],                       
                                [                          
                                        [ "exec", "/sbin/hotplug-call", "%SUBSYSTEM%" ],
                                        [ "load-firmware", "/lib/firmware" ],
                                        [ "return" ]      
                                ]                              
                        ],                                   
                ],                                         
                "remove" : [                                   
                        [ "if",                            
                                [ "and",                       
                                        [ "has", "DEVNAME" ],
                                        [ "has", "MAJOR" ],
                                        [ "has", "MINOR" ],
                                ],          
                                [ "rm", "/dev/%DEVNAME%" ]
                        ]                                                                                          
                ]                                    
        } ],                                                   
        [ "if",                                                                                                    
                [ "eq", "SUBSYSTEM", "platform" ],
                [ "exec", "/sbin/hotplug-call", "%SUBSYSTEM%" ]                                                    
        ],                                                  
        [ "if",                                                
                [ "and",                                
                        [ "has", "BUTTON" ],                
                        [ "eq", "SUBSYSTEM", "button" ],
                ],                                                                                                 
                [ "exec", "/etc/rc.button/%BUTTON%" ]
       ],         
  [ "if",                             
                [ "eq", "SUBSYSTEM",                      
                        [ "net", "input", "usb", "usbmisc", "ieee1394", "block", "atm", "zaptel", "tty", "button" ]
                ],                                      
                [ "exec", "/sbin/hotplug-call", "%SUBSYSTEM%" ]
        ],                                                                                                         
        [ "if",                                   
                [ "and",                                                                                           
                        [ "eq", "SUBSYSTEM", "usb-serial" ],
                        [ "regex", "DEVNAME",                                                                      
                                [ "^ttyUSB", "^ttyACM" ]
                        ],                                     
                ],                                      
                [ "exec", "/sbin/hotplug-call", "tty" ]                                                            
        ],                                           
]

即调用了  /ect/rc.button/下的脚本。自己也可以添加对应的脚本。


本文章由作者:佐须之男 整理编辑,原文地址: WRTnode 2Q 按键驱动说明
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