linux驱动学习2（kpd驱动初步分析）

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;#endiffor (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_AUTOTESTfor (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_EINTmt65xx_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);#endifif(kpd_enable_lprst && get_boot_mode() == NORMAL_BOOT) {kpd_print("Normal Boot\n");#ifdef KPD_PMIC_LPRST_TDkpd_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) = 0if (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。