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;
#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。