Linux内核定时器的使用

内核定时器的结构体定义在include/linux/timer.h：

struct timer_list {
/*
* All fields that change during normal runtime grouped to the
* same cacheline
*/
struct list_head entry;
unsigned long expires;
struct tvec_base *base;

void (*function)(unsigned long);
unsigned long data;

int slack;

#ifdef CONFIG_TIMER_STATS
int start_pid;
void *start_site;
char start_comm[16];
#endif
#ifdef CONFIG_LOCKDEP
struct lockdep_map lockdep_map;
#endif
};

只需初始化定时器的超时时间expires，超时调用函数function，data成员会作为定时器超时函数的参数传递，驱动可以用data来存储自己的私有数据结构地址。下面是定时器应用的一个实例：

驱动的私有数据结构：

struct msg21xx_ts_data {
struct input_dev *input;
struct hrtimer timer;
struct work_struct work;
int irq;
struct dentry *dir;
char *ts_info;
u8 addr;
int fw_major;
int fw_minor;
#ifdef CONFIG_FB
struct notifier_block fb_notif;
#endif
bool suspended;
struct timer_list tp_timer;
struct i2c_client *client;
struct regulator *vdd;
struct regulator *vcc_i2c;
struct msg21xx_platform_data *pdata;
struct workqueue_struct *msg21xx_wq;
struct mutex msg21xx_mutex;
};

驱动的probe函数：

static int msg21xx_ts_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct msg21xx_ts_data *data;

data = kzalloc(sizeof(struct msg21xx_ts_data), GFP_KERNEL);
if (!data) {
dev_err(&client->dev, "%s: Alloc mem fail!", __func__);
err = -ENOMEM;
goto exit;
}

init_timer(&data->tp_timer);
data->tp_timer.function = tp_timer_function;
data->tp_timer.data = (unsigned long)data;
//    setup_timer(&tp_timer, tp_timer_function, (unsigned long)data);
add_timer(&data->tp_timer);
mod_timer(&data->tp_timer, jiffies+HZ * 2);
}

调用init_timer初始化定时器，然后设置定时器的超时调用函数，data成员被初始化为驱动的私有数据结构的地址，最后调用add_timer将定时器加入内核，调用mod_timer后，定时器会在2秒后超时，tp_timer_function函数被调用，data作为函数的参数被传入，在tp_timer_function函数中，就可以操作驱动的硬件。

void tp_timer_function(unsigned long datap)
{
struct msg21xx_ts_data *data = (struct msg21xx_ts_data *)datap;

gpio_set_value_cansleep(data->pdata->home_gpio, 0);
gpio_set_value_cansleep(data->pdata->return_gpio, 0);
gpio_set_value_cansleep(data->pdata->system_gpio, 0);
}

下面的三条语句可以用一条代替：setup_timer(&tp_timer, tp_timer_function, (unsigned long)data);

init_timer(&data->tp_timer);
data->tp_timer.function = tp_timer_function;
data->tp_timer.data = (unsigned long)data;