MTK keypad driver

转自：http://blog.csdn.net/jxnu_xiaobing/article/details/16805623

一、kpd_pdrv_probe函数的分析：

   /*1. 输入设备实例  kpd_input_dev */
 全局变量：static struct input_dev *kpd_input_dev;

  static int kpd_pdrv_probe(struct platform_device *pdev)
 {
     int i, r;
     u16 new_state[KPD_NUM_MEMS];
     /* initialize and register input device (/dev/input/eventX) */



 /*2. 初始化输入设备并分配内存空间*/
     kpd_input_dev = input_allocate_device();
     if (!kpd_input_dev)
         return -ENOMEM;
   /*下面开始填充kpd_input_dev  设备驱动结构体*/
     kpd_input_dev->name = KPD_NAME;
     kpd_input_dev->id.bustype = BUS_HOST;
     kpd_input_dev->id.vendor = 0x2454;
     kpd_input_dev->id.product = 0x6575;
     kpd_input_dev->id.version = 0x0010;
     kpd_input_dev->open = kpd_open;



   /*3. 设置某位为1，以第二个参数为起始地址，EV_KEY表示要设置的位
   作用：告诉input子系统支持那些事件， EV_KEY 这里表示告诉input子系统支持
   按键事件

  */
     __set_bit(EV_KEY, kpd_input_dev->evbit);


 #if (KPD_PWRKEY_USE_EINT||KPD_PWRKEY_USE_PMIC)


   /*4. 设置某位为1，以第二个参数为起始地址，EV_KEY表示要设置的位
   作用：告诉input子系统支持那些按键， KPD_PWRKEY_MAP 这里表示告诉input子系统支持
   电源按键
   */
     __set_bit(KPD_PWRKEY_MAP, kpd_input_dev->keybit);
     kpd_keymap[8] = 0;
 #endif
     for (i = 17; i < KPD_NUM_KEYS; i += 9)   /* only [8] works for Power key */
         kpd_keymap[i] = 0;


     for (i = 0; i < KPD_NUM_KEYS; i++) {
         if (kpd_keymap[i] != 0)
             __set_bit(kpd_keymap[i], kpd_input_dev->keybit);
     }
     /*5. 上述几行代码表示设置电源按键 kpd_keymap 为0，其它按键 kpd_keymap 为1*/

     __set_bit(250, kpd_input_dev->keybit);
     __set_bit(251, kpd_input_dev->keybit);


 #if KPD_AUTOTEST
     for (i = 0; i < ARRAY_SIZE(kpd_auto_keymap); i++)
         __set_bit(kpd_auto_keymap[i], kpd_input_dev->keybit);
 #endif


 #if KPD_HAS_SLIDE_QWERTY
     __set_bit(EV_SW, kpd_input_dev->evbit);
     __set_bit(SW_LID, kpd_input_dev->swbit);
     __set_bit(SW_LID, kpd_input_dev->sw);    /* 1: lid shut => closed */
 #endif


 #ifdef KPD_PMIC_RSTKEY_MAP
     __set_bit(KPD_PMIC_RSTKEY_MAP, kpd_input_dev->keybit);
 #endif


     /*6. 指定kpd_input_dev这个平台设备sysfs中的父设备节点*/
     kpd_input_dev->dev.parent = &pdev->dev;
     /*7. 注册input输入子系统*/
     r = input_register_device(kpd_input_dev);
     if (r) {
         printk(KPD_SAY "register input device failed (%d)\n", r);
         input_free_device(kpd_input_dev);
         return r;
     }


     /* register device (/dev/mt6575-kpd) */
     /*7. 指定kpd_dev这个平台设备sysfs中的父设备节点*/
     kpd_dev.parent = &pdev->dev;
     /*8. 注册混杂设备*/
     r = misc_register(&kpd_dev);
     if (r) {
         printk(KPD_SAY "register device failed (%d)\n", r);
         input_unregister_device(kpd_input_dev);
         return r;
     }

     /*8. 注册按键中断*/
     /* register IRQ and EINT */
     /*9. 设置消抖时间*/
     kpd_set_debounce(KPD_KEY_DEBOUNCE);
     /*10. 设置中断触发方式*/
     mt65xx_irq_set_sens(MT6575_KP_IRQ_ID, MT65xx_EDGE_SENSITIVE);
     /*11 . 设置中断优先级*/
     mt65xx_irq_set_polarity(MT6575_KP_IRQ_ID, MT65xx_POLARITY_LOW);
     /*12. 注册中断处理函数*/
     r = request_irq(MT6575_KP_IRQ_ID, kpd_irq_handler, 0, KPD_NAME, NULL);
     if (r) {
         printk(KPD_SAY "register IRQ failed (%d)\n", r);
         misc_deregister(&kpd_dev);
         input_unregister_device(kpd_input_dev);
         return r;
     }
     /*13. 以下为电源键中断函数的注册*/
 #if KPD_PWRKEY_USE_EINT
     mt65xx_eint_set_sens(KPD_PWRKEY_EINT, KPD_PWRKEY_SENSITIVE);
     mt65xx_eint_set_hw_debounce(KPD_PWRKEY_EINT, KPD_PWRKEY_DEBOUNCE);
     mt65xx_eint_registration(KPD_PWRKEY_EINT, true, KPD_PWRKEY_POLARITY,
                              kpd_pwrkey_eint_handler, false);
 #endif


     if(kpd_enable_lprst && get_boot_mode() == NORMAL_BOOT) {
         kpd_print("Normal Boot\n");
 #ifdef KPD_PMIC_LPRST_TD
         kpd_print("Enable LPRST\n");
     /*14. 以下为设置按键唤醒的时间*/
         upmu_testmode_pwrkey_rst_en(0x01);
         upmu_testmode_homekey_rst_en(0x01);
         upmu_testmode_pwrkey_rst_td(KPD_PMIC_LPRST_TD);
 #endif
     } else {
         kpd_print("Disable LPRST %d\n", kpd_enable_lprst);
     }
     /*15. 设置一个高精度定时器，并且定义了时间到期的回调函数 aee_timer_func*/
     hrtimer_init(&aee_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
     aee_timer.function = aee_timer_func;


     /*以下为三个按键的初始化，也就是配置
     注意，默认值gpio输出是0*/
 #if 1 // ylliu add. dct default value does not work...
     /* KCOL0: GPIO103: KCOL1: GPIO108, KCOL2: GPIO105, KCOL4: GPIO102 input + pull enable + pull up */
     mt_set_gpio_mode(GPIO_KPD_KCOL0_PIN, GPIO_KPD_KCOL0_PIN_M_KP_COL);
     mt_set_gpio_dir(GPIO_KPD_KCOL0_PIN, GPIO_DIR_IN);
     mt_set_gpio_pull_enable(GPIO_KPD_KCOL0_PIN, GPIO_PULL_ENABLE);
     mt_set_gpio_pull_select(GPIO_KPD_KCOL0_PIN, GPIO_PULL_UP);



     mt_set_gpio_mode(GPIO_KPD_KCOL1_PIN, GPIO_KPD_KCOL1_PIN_M_KP_COL);
     mt_set_gpio_dir(GPIO_KPD_KCOL1_PIN, GPIO_DIR_IN);
     mt_set_gpio_pull_enable(GPIO_KPD_KCOL1_PIN, GPIO_PULL_ENABLE);
     mt_set_gpio_pull_select(GPIO_KPD_KCOL1_PIN, GPIO_PULL_UP);

     mt_set_gpio_mode(GPIO_KPD_KCOL2_PIN, GPIO_KPD_KCOL2_PIN_M_KP_COL);
     mt_set_gpio_dir(GPIO_KPD_KCOL2_PIN, GPIO_DIR_IN);
     mt_set_gpio_pull_enable(GPIO_KPD_KCOL2_PIN, GPIO_PULL_ENABLE);
     mt_set_gpio_pull_select(GPIO_KPD_KCOL2_PIN, GPIO_PULL_UP);

     mt_set_gpio_mode(GPIO_KPD_KCOL4_PIN, GPIO_KPD_KCOL4_PIN_M_KP_COL);
     mt_set_gpio_dir(GPIO_KPD_KCOL4_PIN, GPIO_DIR_IN);
     mt_set_gpio_pull_enable(GPIO_KPD_KCOL4_PIN, GPIO_PULL_ENABLE);
     mt_set_gpio_pull_select(GPIO_KPD_KCOL4_PIN, GPIO_PULL_UP);


     /* KROW0: GPIO98, KROW1: GPIO97: KROW2: GPIO95 output + pull disable + pull down */
     mt_set_gpio_mode(GPIO_KPD_KROW0_PIN, GPIO_KPD_KROW0_PIN_M_KP_ROW);
     mt_set_gpio_dir(GPIO_KPD_KROW0_PIN, GPIO_DIR_OUT);
     mt_set_gpio_pull_enable(GPIO_KPD_KROW0_PIN, GPIO_PULL_DISABLE);
     mt_set_gpio_pull_select(GPIO_KPD_KROW0_PIN, GPIO_PULL_DOWN);

 //  mt_set_gpio_mode(97, 1);
 //  mt_set_gpio_dir(97, 1);
 //  mt_set_gpio_pull_enable(97, 0);
 //  mt_set_gpio_pull_select(97, 0);
 //
 //  mt_set_gpio_mode(95, 1);
 //  mt_set_gpio_dir(95, 1);
 //  mt_set_gpio_pull_enable(95, 0);
 //  mt_set_gpio_pull_select(95, 0);
 #endif

     // default disable backlight. reboot from recovery need this.
     kpd_disable_backlight();

     // store default state, resolve recovery bugs.
     kpd_get_keymap_state(new_state);
     memcpy(kpd_keymap_state, new_state, sizeof(new_state));

     return 0;
 }

 
 
二、当执行完面probe函数进行相关初始化后，这时候，当我们按键按下了，就会触发中断，进入中断服务子程序

 static irqreturn_t __tcmfunc kpd_irq_handler(int irq, void *dev_id)
 {
     /* use _nosync to avoid deadlock */
     disable_irq_nosync(MT6575_KP_IRQ_ID);
     tasklet_schedule(&kpd_keymap_tasklet);
     return IRQ_HANDLED;
 }

可以看到，中断服务程序里面执行了 tasklet_schedule(&kpd_keymap_tasklet);
跟踪代码可以发现，实际上是执行了这个函数kpd_keymap_handler，下面仔细分析
这个函数，详细注释如下：

 static void kpd_keymap_handler(unsigned long data)
 {
     int i, j;
     bool pressed;
     u16 new_state[KPD_NUM_MEMS], change, mask;
     u16 hw_keycode, linux_keycode;
     kpd_get_keymap_state(new_state);                                                                    //首先读取键值，并且存放于new_state中


     if (pmic_get_acc_state() == 1) {
     for (i = 0; i < KPD_NUM_MEMS; i++) {
         change = new_state[i] ^ kpd_keymap_state[i];                                        //进行异或操作，就是为了取出两者不同的值
         if (!change)
             continue;


         for (j = 0; j < 16; j++) {
             mask = 1U << j;
             if (!(change & mask))
                 continue;


             hw_keycode = (i << 4) + j;        //i = 0, j = 1;                                 //这里是得到hw_keycode的值
             printk("hw_keycode = %d ,i = %d, j = %d \n",hw_keycode,i,j);
             /* bit is 1: not pressed, 0: pressed */
             pressed = !(new_state[i] & mask);   //(new_state[i] & mask) = 0
             if (kpd_show_hw_keycode) {
                 printk(KPD_SAY "(%s) HW keycode = %u\n",
                        pressed ? "pressed" : "released",
                        hw_keycode);
             }
             BUG_ON(hw_keycode >= KPD_NUM_KEYS);
             linux_keycode = kpd_keymap[hw_keycode];                                             //这里的linux_keycode恒为零。
             printk("linux_keycode = %d  \n",linux_keycode);

             if(unlikely(linux_keycode == 0)) {
                 if (hw_keycode == 1 && pressed) { // special key, SOS.
                     struct device *dev = &(kpd_input_dev->dev);
                     char *envp[] = { "SOS_pressed", NULL };
                     kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, envp);               //建立设备文件？
                     printk(KPD_SAY "SOS_pressed\n");
                     // used by recovery.
                     /*这个接口会向INPUT子系统上报按键（该按键被按下）*/
                     input_report_key(kpd_input_dev, 251, pressed);                      //如果上层检测到SOS_pressed就会做相应处理。
                 } else if (hw_keycode == 2 && pressed) { // special key, background.
                     struct device *dev = &(kpd_input_dev->dev);
                     char *envp[] = { "background_pressed", NULL };
                     kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, envp);
                     printk(KPD_SAY "background_pressed\n");
                     // used by recovery.
                     input_report_key(kpd_input_dev, 8, pressed);
                 } else if (hw_keycode == 4 && pressed) { // special key, mode.
                     struct device *dev = &(kpd_input_dev->dev);
                     char *envp[] = { "mode_pressed", NULL };
                     kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, envp);
                     printk(KPD_SAY "mode_pressed\n");
                 } else if (hw_keycode == 1 || hw_keycode == 2 || hw_keycode == 4) { // add this to turn off backlight.
                     printk(KPD_SAY "background or SOS or mode release!\n");
                     // used by recovery.
                     if (hw_keycode == 1)
                         input_report_key(kpd_input_dev, 251, pressed);
                     else if (hw_keycode == 2)
                         input_report_key(kpd_input_dev, 8, pressed);
                 } else {
                     kpd_print("Linux keycode = 0\n");
                     continue;
                 }
             }
             kpd_aee_handler(linux_keycode, pressed);
             kpd_backlight_handler(pressed, linux_keycode);
             input_report_key(kpd_input_dev, linux_keycode, pressed);
         }
     }
     } else {
         printk(KPD_SAY "acc off, ignore and key...\n");
     }

     memcpy(kpd_keymap_state, new_state, sizeof(new_state));


     kpd_print("save new keymap state\n");
     enable_irq(MT6575_KP_IRQ_ID);
 }

三、kpd_aee_handler函数分析

 static void kpd_aee_handler(u32 keycode, u16 pressed) {
     if(pressed) {
         if(keycode == KEY_VOLUMEUP) {
             __set_bit(0, &aee_pressed_keys);
         } else if(keycode == KEY_VOLUMEDOWN) {
             __set_bit(1, &aee_pressed_keys);
         } else {
             return;
         }
         kpd_update_aee_state();
     } else {
         if(keycode == KEY_VOLUMEUP) {
             __clear_bit(0, &aee_pressed_keys);
         } else if(keycode == KEY_VOLUMEDOWN) {
             __clear_bit(1, &aee_pressed_keys);
         } else {
             return;
         }
         kpd_update_aee_state();
     }
 }

详细分析：
1.__set_bit(0, &aee_pressed_keys)，定义了一个：static u16 aee_pressed_keys;
所以__set_bit的意思是将aee_pressed_keys的bit0设置为1
2.相应的__clear_bit(0, &aee_pressed_keys);就是把aee_pressed_keys的bit0清零，
3.还有在内核的non-atomic.h文件中还有一些其它的位操作，记住__set_bit和set_bit的区别就
是前者是非原子操作，而后者是原子操作，所谓原子操作，意思是最小的执行单位，再其执行过
程中是不会被其他任务打断的。


四、背光处理函数

 void kpd_backlight_handler(bool pressed, u16 linux_keycode)
 {
     if (kpd_suspend && !test_bit(linux_keycode, kpd_wake_keybit)) {
         kpd_print("Linux keycode %u is not WAKE key\n", linux_keycode);
         return;
     }
     /* not in suspend or the key pressed is WAKE key */
     if (pressed) {
         atomic_inc(&kpd_key_pressed);
         kpd_backlight_on = !!atomic_read(&kpd_key_pressed);
         schedule_work(&kpd_backlight_work);     //点亮背光灯
         kpd_print("switch backlight on\n");
     } else {
         atomic_dec(&kpd_key_pressed);
         mod_timer(&kpd_backlight_timer,             //KPD_BACKLIGHT_TIME控制背光时间，单位为sec，如果注释掉这句，背光将不灭
                   jiffies + KPD_BACKLIGHT_TIME * HZ);
         kpd_print("activate backlight timer\n");
     }
 }

详细分析
1.首先用到了一个位操作函数，注意这个函数是原子操作test_bit
2.全局变量static atomic_t kpd_key_pressed = ATOMIC_INIT(0);这是原子操作的初始化，kpd_key_pressed初始化为0
3.上述函数涉及到一些原子操作函数，解释如下：
atomic_inc(&kpd_key_pressed); 是对变量进行加1操作
atomic_dec(&kpd_key_pressed); 是对变量进行减1操作
!!atomic_read(&kpd_key_pressed);是读取变量的值，前面两个 !!强调该返回值不是1就是0：bool类型
4.mod_timer：该函数的作用是修改一个已经调度的定时器结构的到期时间。


五、背光控制函数


调度的是这个函数

 static void kpd_switch_backlight(struct work_struct *work)
 {
     if (kpd_backlight_on) {
         kpd_enable_backlight();
         kpd_print("backlight is on\n");
     } else {
         kpd_disable_backlight();
         kpd_print("backlight is off\n");
     }
 }

这里就能够看到使能和失能背光的函数，继续跟踪：

 void kpd_enable_backlight(void)
 {
     /*mt6326_kpled_dim_duty_Full();
     mt6326_kpled_Enable();*/
     upmu_kpled_dim_duty(31);
     upmu_kpled_en(1);
 }
 upmu_kpled_dim_duty这是控制背光电流大小从而可以控制亮度
 upmu_kpled_en这是控制开关。

mod_timer函数的补充

http://www.360doc.com/content/12/0510/11/6973384_210041084.shtml

kpd驱动初步分析完毕。