20211227使用devm_extcon_dev_register架构上报拔出插入事件，demo实例测试extcon，app通过广播接收这个消息

一、kernel 驱动代码&＃xff0c;注册成功后会生成/sys/class/extcon/extcon-demo这个文件夹

1、dts和extcon文件的修改

diff --git a/arch/arm64/boot/dts/rockchip/rk3566-rk817-tablet.dts b/arch/arm64/boot/dts/rockchip/rk3566-rk817-tablet.dts
index 483068a..4175b75 100755
--- a/arch/arm64/boot/dts/rockchip/rk3566-rk817-tablet.dts
&＃43;&＃43;&＃43; b/arch/arm64/boot/dts/rockchip/rk3566-rk817-tablet.dts
&＃64;&＃64; -157,7 &＃43;157,10 &＃64;&＃64;pinctrl-0 &＃61; <&hp_det>;io-channels &＃61; <&saradc 2>;};
-
&＃43; extcon_demo: extcon-demo {
&＃43; compatible &＃61; "extcon_demo";
&＃43; status &＃61; "okay";
&＃43; };sdio_pwrseq: sdio-pwrseq {compatible &＃61; "mmc-pwrseq-simple";clocks &＃61; <&rk817 1>;
diff --git a/drivers/extcon/extcon.c b/drivers/extcon/extcon.c
old mode 100644
new mode 100755
index def0649..df2f628
--- a/drivers/extcon/extcon.c
&＃43;&＃43;&＃43; b/drivers/extcon/extcon.c
&＃64;&＃64; -121,6 &＃43;121,16 &＃64;&＃64; static const struct __extcon_info {.id &＃61; EXTCON_JACK_HEADPHONE,.name &＃61; "HEADPHONE",},
&＃43; [EXTCON_DEMO_B] &＃61; {
&＃43; .type &＃61; EXTCON_TYPE_MISC,
&＃43; .id &＃61; EXTCON_DEMO_B,
&＃43; .name &＃61; "EXTCON_DEMO_BJAP",
&＃43; },
&＃43; [EXTCON_DEMO_A] &＃61; {
&＃43; .type &＃61; EXTCON_TYPE_MISC,
&＃43; .id &＃61; EXTCON_DEMO_A,
&＃43; .name &＃61; "EXTCON_DEMO_AENG",
&＃43; },[EXTCON_JACK_LINE_IN] &＃61; {.type &＃61; EXTCON_TYPE_JACK,.id &＃61; EXTCON_JACK_LINE_IN,
diff --git a/include/linux/extcon.h b/include/linux/extcon.h
old mode 100644
new mode 100755
index dfe0b89..82a93c1
--- a/include/linux/extcon.h
&＃43;&＃43;&＃43; b/include/linux/extcon.h
&＃64;&＃64; -91,7 &＃43;91,11 &＃64;&＃64;#define EXTCON_JIG 61#define EXTCON_MECHANICAL 62-#define EXTCON_NUM 63
&＃43;#define EXTCON_DEMO_A 64
&＃43;#define EXTCON_DEMO_B 65
&＃43;
&＃43;
&＃43;#define EXTCON_NUM 66/** Define the properties of supported external connectors.


1、\kernel\drivers\char\extcon_demo.c


#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include /*驱动注册的头文件&＃xff0c;包含驱动的结构体和注册和卸载的函数*/
#include #define DRIVER_NAME "extcon_demo"MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("TOPEET");struct extcon_dev *edev;static const unsigned int headset_cable[] &＃61; {EXTCON_JACK_MICROPHONE,EXTCON_JACK_HEADPHONE,EXTCON_NONE,
};static const unsigned int extcon_demo_cable[] &＃61; {EXTCON_DEMO_B,EXTCON_DEMO_A,EXTCON_NONE,
};static ssize_t extcon_demo_show(struct device *dev, struct device_attribute *attr, char *buf)
{printk("extcon_demo_show!\n");//extcon_set_state_sync(edev,// EXTCON_JACK_MICROPHONE, true);extcon_set_state_sync(edev,EXTCON_DEMO_B, true);return 0;
}static ssize_t extcon_demo_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{printk("extcon_demo_store\n");//extcon_set_state_sync(edev,// EXTCON_JACK_MICROPHONE, false);extcon_set_state_sync(edev,EXTCON_DEMO_B, false);return count;
}
static DEVICE_ATTR(state, 0664, extcon_demo_show, extcon_demo_store);static int extcon_demo_probe(struct platform_device *pdv){int err;int ret;printk(KERN_EMERG "\tinitialized\n");//edev &＃61; devm_extcon_dev_allocate(&pdv->dev, headset_cable);//extcon_demo_cableedev &＃61; devm_extcon_dev_allocate(&pdv->dev, extcon_demo_cable);//ret &＃61; devm_extcon_dev_register(&pdv->dev, edev);err &＃61; device_create_file(&pdv->dev, &dev_attr_state);if (err)printk(KERN_EMERG "\tdevice_create_file_error\n");elseprintk(KERN_EMERG "\t very good device_create_file_success\n");return 0;
}static int extcon_demo_remove(struct platform_device *pdv){return 0;
}
static void extcon_demo_shutdown(struct platform_device *pdv){;
}static int extcon_demo_resume(struct platform_device *pdv){return 0;
}static const struct of_device_id extcon_demo_of_match[] &＃61; {{ .compatible &＃61; "extcon_demo", },{},
};MODULE_DEVICE_TABLE(of, extcon_demo_of_match);struct platform_driver extcon_demo_driver &＃61; {.probe &＃61; extcon_demo_probe,.remove &＃61; extcon_demo_remove,.shutdown &＃61; extcon_demo_shutdown,.resume &＃61; extcon_demo_resume,.driver &＃61; {.name &＃61; DRIVER_NAME,.owner &＃61; THIS_MODULE,.of_match_table &＃61; of_match_ptr(extcon_demo_of_match),}
};static int extcon_demo_init(void)
{int DriverState;printk(KERN_EMERG "HELLO WORLD enter! extcon_demo\n");DriverState &＃61; platform_driver_register(&extcon_demo_driver);printk(KERN_EMERG "\t DriverState extcon_demo is %d\n",DriverState);return 0;
}static void extcon_demo_exit(void)
{printk(KERN_EMERG "HELLO WORLD exit!\n");platform_driver_unregister(&extcon_demo_driver);
}module_init(extcon_demo_init);
module_exit(extcon_demo_exit);

3、注册成功

二、上层接收这个消息的代码

1、frameworks\base\services\core\java\com\android\server\WiredAccessoryManager.java 里面的parseState和updateState更新信息。

 2、parseState和updateState在frameworks\base\services\core\java\com\android\server\ExtconStateObserver.java里面的onUEvent函数调用

 3、上面的onUEvent函数在  \frameworks\base\core\java\android\os\UEventObserver.java里面的的sendEvent调用。

  4、sendEvent在同文件的run里面调用。

   5、上面的nativeSetup和nativeWaitForNextEvent是jni获取底层的信息。nativeWaitForNextEvent里面会调用uevent_next_event&＃xff0c; frameworks\base\core\jni\android_os_UEventObserver.cpp

    6、上面的uevent_next_event是在hardware\libhardware_legacy\uevent.c&＃xff0c;这个文件里面是读底层信息&＃xff0c;这里把整个代码的贴出来。

/** Copyright (C) 2008 The Android Open Source Project** Licensed under the Apache License, Version 2.0 (the "License");* you may not use this file except in compliance with the License.* You may obtain a copy of the License at** http://www.apache.org/licenses/LICENSE-2.0** Unless required by applicable law or agreed to in writing, software* distributed under the License is distributed on an "AS IS" BASIS,* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License.*/#include #include
#include
#include
#include
#include #include
#include
#include
#include LIST_HEAD(uevent_handler_head, uevent_handler) uevent_handler_list;
pthread_mutex_t uevent_handler_list_lock &＃61; PTHREAD_MUTEX_INITIALIZER;struct uevent_handler {void (*handler)(void *data, const char *msg, int msg_len);void *handler_data;LIST_ENTRY(uevent_handler) list;
};static int fd &＃61; -1;/* Returns 0 on failure, 1 on success */
int uevent_init()
{struct sockaddr_nl addr;int sz &＃61; 64*1024;int s;memset(&addr, 0, sizeof(addr));addr.nl_family &＃61; AF_NETLINK;addr.nl_pid &＃61; getpid();addr.nl_groups &＃61; 0xffffffff;s &＃61; socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);if(s <0)return 0;setsockopt(s, SOL_SOCKET, SO_RCVBUFFORCE, &sz, sizeof(sz));if(bind(s, (struct sockaddr *) &addr, sizeof(addr)) <0) {close(s);return 0;}fd &＃61; s;return (fd > 0);
}int uevent_get_fd()
{return fd;
}int uevent_next_event(char* buffer, int buffer_length)
{while (1) {struct pollfd fds;int nr;fds.fd &＃61; fd;fds.events &＃61; POLLIN;fds.revents &＃61; 0;nr &＃61; poll(&fds, 1, -1);if(nr > 0 && (fds.revents & POLLIN)) {int count &＃61; recv(fd, buffer, buffer_length, 0);if (count > 0) {struct uevent_handler *h;pthread_mutex_lock(&uevent_handler_list_lock);LIST_FOREACH(h, &uevent_handler_list, list)h->handler(h->handler_data, buffer, buffer_length);pthread_mutex_unlock(&uevent_handler_list_lock);return count;} }}// won&＃39;t get herereturn 0;
}int uevent_add_native_handler(void (*handler)(void *data, const char *msg, int msg_len),void *handler_data)
{struct uevent_handler *h;h &＃61; malloc(sizeof(struct uevent_handler));if (h &＃61;&＃61; NULL)return -1;h->handler &＃61; handler;h->handler_data &＃61; handler_data;pthread_mutex_lock(&uevent_handler_list_lock);LIST_INSERT_HEAD(&uevent_handler_list, h, list);pthread_mutex_unlock(&uevent_handler_list_lock);return 0;
}int uevent_remove_native_handler(void (*handler)(void *data, const char *msg, int msg_len))
{struct uevent_handler *h;int err &＃61; -1;pthread_mutex_lock(&uevent_handler_list_lock);LIST_FOREACH(h, &uevent_handler_list, list) {if (h->handler &＃61;&＃61; handler) {LIST_REMOVE(h, list);err &＃61; 0;break;}}pthread_mutex_unlock(&uevent_handler_list_lock);return err;
}


    7、开始StartWiredAccessoryManager&＃xff0c;frameworks\base\services\java\com\android\server\SystemServer.java

三、上面的分析完了&＃xff0c;我们来实际测试一下底层发信息到上层&＃xff0c;从log上看&＃xff0c;WiredAccessoryManager.java里面接受到底层通过extcon架构发过来的信息。

四、那app如何收到这个变化的信息呢&＃xff1f;解决方案是发广播&＃xff0c;然后app接收这个广播。我这里是为了测试&＃xff0c;用一个reboot的广播代码&＃xff0c;代码修改如下。执行cat   /sys/devices/platform/extcon-demo/state 后&＃xff0c;WiredAccessoryManager里面接受到信息后会发reboot广播&＃xff0c;机器会reboot。

五、参考文章&＃xff1a;

Android驱动——audio输入输出插拔检测_zhaojy5453的博客-CSDN博客

Android HDMI audio设备插拔事件_代码搬运工小弟的博客-CSDN博客_android audio hdmi