Linux high-precision timer example

//author:DriverMonkey//phone:13410905075//mail:bookworepeng@Hotmail.com//qq:196568501#include <linux/kernel.h>  #include <linux/module.h>  #include <linux/cdev.h>  #include <linux/fs.h>  #include <linux/device.h>  #include <linux/syscalls.h>#include <linux/interrupt.h> #include <linux/gpio.h>#include <linux/of_gpio.h>#include <linux/of_platform.h>#include <linux/uaccess.h>  #include <linux/string.h> #include <mach/gpio.h>#include <mach/irqs.h>#define GPIO_TO_PIN(bank, gpio) (32 * (bank) + (gpio))#define US (1000)#define PPM_CHANEL 8#define FIX_LOW_TIME 100*USstruct ppm_dev  {      struct cdev cdev;      dev_t devno;      struct class *ppm_class; int message_cdev_open;}; struct ppm_dev ppm_dev;  static long long ppm_values[(PPM_CHANEL + 1)*2] =    {FIX_LOW_TIME,1000*US,  // 1   FIX_LOW_TIME,1000*US,// 2   FIX_LOW_TIME,1000*US,// 3   FIX_LOW_TIME,1000*US,  // 4   FIX_LOW_TIME,1000*US,// 5   FIX_LOW_TIME,1000*US,// 6   FIX_LOW_TIME,1000*US,// 7   FIX_LOW_TIME,1000*US,// 8   FIX_LOW_TIME,5000*US, };// 9ktime_t ktime;static struct hrtimer hr_timer;static enum hrtimer_restart hrtimer_callback(struct hrtimer *timer){static int index = 0;static ktime_t ktime;if(index == ((PPM_CHANEL + 1)*2))index = 0;ktime.tv64 = ppm_values[index];hrtimer_forward(timer, timer->base->get_time(), ktime);index++;if(ktime.tv64 == FIX_LOW_TIME)gpio_direction_output(GPIO_TO_PIN(0,27), 0);elsegpio_direction_output(GPIO_TO_PIN(0,27), 1);//printk("%d\n",(int)ktime.tv64);return HRTIMER_RESTART;}static int ppm_open(struct inode *node, struct file *fd)  {  int ret = 0;printk("ppm_open()++\n"); ktime = ktime_set( 0, 200*1000);   // 200ushrtimer_init( &hr_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL );hr_timer.function = &hrtimer_callback;hrtimer_start( &hr_timer, ktime, HRTIMER_MODE_REL );    printk("ppm_open()--\n");        return ret;  }    ssize_t ppm_write(struct file *pfile,  const char __user *buffer,  size_t size,  loff_t *pnull) {printk("ppm_write()++\n");if(size != (PPM_CHANEL * sizeof(long long)))return 0;//copy_from_user(ppm_values, buffer, size);printk("ppm_write()--\n");return size;}static int ppm_fasync(int fd, struct file *filp, int mode){printk("ppm_fasync()++\n");printk("ppm_fasync()--\n");return 0;}static int ppm_release(struct inode *node, struct file *fd)  {  printk("ppm_release()++\n"); hrtimer_cancel(&hr_timer);    printk("ppm_release()--\n");      return 0;  } struct file_operations meassage_operatons =  {      .owner = THIS_MODULE,      .open = ppm_open,      .write = ppm_write,    .fasync = ppm_fasync,    .release = ppm_release,  };    static int __init ppm_init(void)  {      struct ppm_dev * dev;  int ret = 0;      dev = &ppm_dev;      alloc_chrdev_region(&dev->devno, 0, 1, "out_ppm");      dev->ppm_class = class_create(THIS_MODULE, "ppm_class");      if(IS_ERR(dev->ppm_class)) {           printk(KERN_ERR"Err: failed in creating class./n");           goto fail1;        }      device_create(dev->ppm_class, NULL, dev->devno, NULL, "ppm");  //init irqret = gpio_request(GPIO_TO_PIN(0,27), "ppm_inter");if(ret){printk(KERN_ERR"gpio_request() failed !\n");goto fail1;}ret = gpio_direction_output(GPIO_TO_PIN(0,27), 1);if(ret){printk(KERN_ERR"gpio_direction_input() failed !\n");goto fail2;}    cdev_init(&dev->cdev, &meassage_operatons);      cdev_add(&dev->cdev, dev->devno, 1);  if(ret){printk(KERN_ERR"request_irq() failed ! %d\n", ret);goto fail2;}   printk("ppm_to_app_init(void)--\n");          return 0;  fail2:gpio_free(GPIO_TO_PIN(0,27));fail1:    device_destroy(dev->ppm_class, dev->devno);      class_destroy(dev->ppm_class);       cdev_del(&dev->cdev);      unregister_chrdev_region(dev->devno, 1);  return ret;}  static void __exit ppm_exit(void)  {      struct ppm_dev *dev = &ppm_dev;       // printk("ppm_to_app_exit(void)++\n");    gpio_free(GPIO_TO_PIN(0,27));    device_destroy(dev->ppm_class, dev->devno);      class_destroy(dev->ppm_class);       cdev_del(&dev->cdev);      unregister_chrdev_region(dev->devno, 1);            // printk("ppm_to_app_exit(void)--\n");  }  module_init(ppm_init);  module_exit(ppm_exit);    MODULE_LICENSE("GPL");  MODULE_AUTHOR("Driver Monkey");  MODULE_DESCRIPTION("Test ppm");