linux驱动9--ldd中第七章时间 延时及延缓操作

1. timer
每隔8个jiffies,打印一个hello

#include <linux/init.h>
#include <linux/module.h>
#include <linux/types.h>
struct timer_list timer;
static void do_timer_process(unsigned long arg)
{
    printk("%s\n", (char*)arg);
    timer.expires    = jiffies +8;
    add_timer(&timer);
}

static int __init scull_init(void)
{
    printk(KERN_ALERT "enter scull dirver\n");
    setup_timer(&timer, do_timer_process, (unsigned long)"Hello");
    timer.expires    = jiffies +8;
    add_timer(&timer);
    return 0;
}

static void __exit scull_exit(void)
{
    printk(KERN_ALERT "goodbye scull dirver\n");
    return ;
}

MODULE_LICENSE("GPL");

module_init(scull_init);
module_exit(scull_exit);

2.高精度定时器:
  利用hrtimer延时8ms

#include <linux/init.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/dma-mapping.h>
#include <linux/hrtimer.h>
#include <linux/time.h>
#include <linux/timer.h>
#include <linux/timex.h>
#include <linux/rtc.h>
#define dbmsg(fmt, args ...) printk(KERN_NOTICE "%s[%d]: "fmt"\n", __FUNCTION__, __LINE__,##args)
static struct hrtimer vibe_timer;
static int value = 8; //delay 8ms
static enum hrtimer_restart vibrator_timer_func(struct hrtimer *timer)
{
    struct timeval tv;
    do_gettimeofday(&tv);
    dbmsg("time %u:%u",tv.tv_sec,tv.tv_usec);
    vibe_timer.function = vibrator_timer_func;
    hrtimer_start(&vibe_timer, ktime_set(value / 1000, (value % 1000) * 1000000),HRTIMER_MODE_REL);
    return HRTIMER_NORESTART;
}

static int scull_init(void)
{
    dbmsg("scull_init");
    hrtimer_init(&vibe_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
    vibe_timer.function = vibrator_timer_func;
    hrtimer_start(&vibe_timer, ktime_set(value / 1000, (value % 1000) * 1000000),HRTIMER_MODE_REL);
    return 0;
}

static void scull_exit(void)
{
    while(hrtimer_cancel(&vibe_timer))
    {
        dbmsg("scull exit");
    }
}

MODULE_LICENSE("GPL");

module_init(scull_init);
module_exit(scull_exit);

打印结果:
lcm3d: vibrator_timer_func[20]: time 87433:710
lcm3d: vibrator_timer_func[20]: time 87433:10708
lcm3d: vibrator_timer_func[20]: time 87433:20702
lcm3d: vibrator_timer_func[20]: time 87433:30706
lcm3d: vibrator_timer_func[20]: time 87433:40702
lcm3d: vibrator_timer_func[20]: time 87433:50702
注:从上述打印来看,大约每次执行了10ms,但是去掉打印从示波器上看的确是8ms

3. 工作队列延时

#include <linux/init.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/dma-mapping.h>
#include <linux/hrtimer.h>
#include <linux/time.h>
#include <linux/timer.h>
#include <linux/timex.h>
#include <linux/rtc.h>
#define dbmsg(fmt, args ...) printk(KERN_NOTICE "lcm3d: %s[%d]: "fmt"\n", __FUNCTION__, __LINE__,##args)

struct delayed_work dwork;
static void dwork_func(void)
{
    unsigned long delay = msecs_to_jiffies(8);  //每8ms执行一次
    schedule_delayed_work(&dwork, delay);
    dbmsg("in dwork_func");
}
static int scull_init(void)
{
    dbmsg("scull_init");
    INIT_DELAYED_WORK(&dwork, dwork_func);
    schedule_work(&dwork); //by feng
    return 0;
}

static void scull_exit(void)
{
    dbmsg("scull exit");
}

MODULE_LICENSE("GPL");

module_init(scull_init);
module_exit(scull_exit);

4. 工作队列的一个例子

#include <linux/init.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/workqueue.h>
struct timer_list timer;
struct work_struct my_work;
struct workqueue_struct *my_work_queue;
static void my_work_process(struct work_struct *work)
{
    printk("my_work_process \n");
    return ;
}

static void do_timer_process(unsigned long arg)
{
    //3.将工作提交到工作队列
    queue_work(my_work_queue, &my_work);

    timer.expires = jiffies +8;
    add_timer(&timer);
}
static int __init scull_init(void)
{
    printk(KERN_ALERT "enter scull dirver\n");
    //创建工作队列
    //  1. 填充一个work_struct
    //  2. 显式的创建一个工作队列
    INIT_WORK(&my_work, my_work_process);
    my_work_queue = create_workqueue("my_work");

    //setup timer
    setup_timer(&timer, do_timer_process, (unsigned long)"Hello");
    timer.expires = jiffies +8;
    add_timer(&timer);
    return 0;
}
static void __exit scull_exit(void)
{
    printk(KERN_ALERT "goodbye scull dirver\n");
    return ;
}
MODULE_LICENSE("GPL");
module_init(scull_init);
module_exit(scull_exit);

5. 工作队列中参数的传递

#include <linux/init.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/workqueue.h>
#include <linux/slab.h>

struct timer_list timer;
struct _work_s
{
    struct work_struct wk;
    struct workqueue_struct *wkq;
    char data[20];
};
typedef struct _work_s work_s;
static void my_work_process(struct work_struct *work)
{
    //利用container_of获取结构体,然后取得参数
    work_s* my_work= container_of(work, work_s, wk);
    printk("my_work_process data=%s\n", my_work->data);
    return ;
}

static void do_timer_process(unsigned long arg)
{
    work_s * my_work = (work_s*)arg;    //获取work_s结构体
    // 3.将工作提交到工作队列
    queue_work(my_work->wkq, &my_work->wk);
    timer.expires = jiffies +8;
    add_timer(&timer);
}
static int __init scull_init(void)
{
    work_s* my_work = NULL;
    my_work = kzalloc(sizeof(work_s), GFP_KERNEL);
    printk(KERN_ALERT "enter scull dirver\n");
    //创建工作队列
    //  1. 填充一个work_struct
    //  2. 显式的创建一个工作队列
    INIT_WORK(&my_work->wk, my_work_process);
    my_work->wkq= create_workqueue("my_work");
    memcpy(my_work->data, "hello", 6);
    //setup timer
    //将结构体当作参数传递出去
    setup_timer(&timer, do_timer_process, (unsigned long)my_work);
    timer.expires = jiffies +8;
    add_timer(&timer);
    return 0;
}
static void __exit scull_exit(void)
{
    printk(KERN_ALERT "goodbye scull dirver\n");
    return ;
}
MODULE_LICENSE("GPL");
module_init(scull_init);
module_exit(scull_exit);