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
1 2 3 4 5 6 7 8 9 10 11 12 | #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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | 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
1 2 3 | 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：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 | [ [ "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。
