耳機驅動程式上報

上報設備

1. headset ：聽筒mic
2. headphone：聽筒沒有mic
3. Lineout：聲音輸出沒有mic

上報方式

1. 輸入子系統：
   • 可上報輸入事件
   • 上報開關事件
2. switch state：uevent

編寫輸入系統驅動

1. 分配input_dev；
2. 設置：
   1. 能產生哪類事件：EV_SW
   2. 能產生EV_SW中的哪些事件
      • headset
      • headphone
      • Lineout
3. 註冊input_dev
4. 硬體相關（中斷程式）
   • 上報插入事件
   • 上報拔出事件

#include <linux/module.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/err.h>
#include <linux/switch.h>
#include <linux/input.h>

static struct input_dev *g_virtual_input;

static ssize_t input_test_store(struct device *dev,
                     struct device_attribute *attr,
                     const char *buf, size_t count)
{
    long code;
    long val;
    char *endp;

    /* 如果字元串前面含有非數字, simple_strtol不能處理 */
    while ((*buf == ' ') || (*buf == '\t'))
        buf++;

    code = simple_strtol(buf, &endp, 0);

    /* 如果字元串前面含有非數字, simple_strtol不能處理 */
    while ((*endp == ' ') || (*endp == '\t'))
        endp++;
    val  = simple_strtol(endp, NULL, 0);

    printk("emulate to report EV_SW: 0x%x 0x%x\n", code, val);
    input_event(g_virtual_input, EV_SW, code, val);
    input_sync(g_virtual_input);

    return count;
}

static DEVICE_ATTR(test_input, S_IRUGO | S_IWUSR, NULL, input_test_store);

static int register_input_device_for_jack(void)
{
    int err;
    
    /* 分配input_dev */
    g_virtual_input = input_allocate_device();

    /* 設置 */
    /* 2.1 能產生哪類事件 */
    set_bit(EV_SYN, g_virtual_input->evbit);
    set_bit(EV_SW, g_virtual_input->evbit);


    /* 2.2 能產生這類事件中的哪些 */
    /* headset = 聽筒 + MIC = SW_HEADPHONE_INSERT + SW_MICROPHONE_INSERT
     *    同時上報 SW_HEADPHONE_INSERT 和 SW_MICROPHONE_INSERT, 就表示headset
     *    為了簡化, 對於android系統只上報SW_MICROPHONE_INSERT也表示headset
     */
    set_bit(SW_HEADPHONE_INSERT, g_virtual_input->swbit);
    set_bit(SW_MICROPHONE_INSERT, g_virtual_input->swbit);
    set_bit(SW_LINEOUT_INSERT, g_virtual_input->swbit);

    /* 2.3 這些事件的範圍 */

    g_virtual_input->name = "alsa_switch"; /* 不重要 */

    /* 註冊 */
    err = input_register_device(g_virtual_input);
    if (err) {
        input_free_device(g_virtual_input); 
        printk("input_register_device for virtual jack err!\n");
        return err;
    }

    /* 創建/sys/class/input/inputX/test_input文件
     *   可以執行類似下麵的命令來模擬耳麥的動作:  
     *       觸發上報headset插入: echo 4 1 > /sys/class/input/inputX/test_input  
     *       觸發上報headset取下: echo 4 0 > /sys/class/input/inputX/test_input  
     */
    err = device_create_file(&g_virtual_input->dev, &dev_attr_test_input);
    if (err) {
        printk("device_create_file for test_input err!\n");
        input_unregister_device(g_virtual_input);
        input_free_device(g_virtual_input); 
        return err;
    }

    return 0;
}

static void unregister_input_device_for_jack(void)
{
    device_remove_file(&g_virtual_input->dev, &dev_attr_test_input);

    input_unregister_device(g_virtual_input);
    input_free_device(g_virtual_input); 
}


/**************************************************************************************************************/

static struct switch_dev g_virtual_switch;

static ssize_t state_test_store(struct device *dev,
                     struct device_attribute *attr,
                     const char *buf, size_t count)
{
    long val;

    val = simple_strtol(buf, NULL, 0);

    printk("emulate to report swtich state: 0x%x\n", val);
    switch_set_state(&g_virtual_switch, val);

    return count;
}

static DEVICE_ATTR(test_state, S_IRUGO | S_IWUSR, NULL, state_test_store);

static int register_switch_device_for_jack(void)
{
    int err;
    
    g_virtual_switch.name = "h2w";
    err = switch_dev_register(&g_virtual_switch);
    if (err) {
        printk("switch_dev_register h2w err!\n");
        return err;
    }

    /* 創建/sys/class/switch/h2w/test_state文件
     *   可以執行類似下麵的命令來模擬耳麥的動作:  
     *       觸發上報headset插入: echo 1 > /sys/class/switch/h2w/test_state
     *       觸發上報headset取下: echo 0 > /sys/class/switch/h2w/test_state
     */
    err = device_create_file(g_virtual_switch.dev, &dev_attr_test_state);
    if (err) {
        printk("device_create_file test err!\n");
        switch_dev_unregister(&g_virtual_switch);
        return err;
    }

    return 0;
}

static void unregister_switch_device_for_jack(void)
{
    device_remove_file(g_virtual_switch.dev, &dev_attr_test_state);
    switch_dev_unregister(&g_virtual_switch);
}

/**************************************************************************************************************/

static int __init virtual_jack_init(void)
{
    int err;
    
    err = register_input_device_for_jack();
    err = register_switch_device_for_jack();
    
    return 0;
}

static void __exit virtual_jack_exit(void)
{
    unregister_input_device_for_jack();
    unregister_switch_device_for_jack();
}

module_init(virtual_jack_init);
module_exit(virtual_jack_exit);

MODULE_AUTHOR("[email protected]");
MODULE_DESCRIPTION("Virutal jack driver for sound card");
MODULE_LICENSE("GPL");