看代码注释_tmp &= ~(1<<14)_6410 pwm0驱动修改说明

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/poll.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/interrupt.h>
#include <asm/uaccess.h>
#include <mach/hardware.h>
#include <plat/regs-timer.h>
#include <mach/regs-irq.h>
#include <asm/mach/time.h>
#include <linux/clk.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/miscdevice.h>

#include <mach/map.h>
#include <mach/regs-clock.h>
#include <mach/regs-gpio.h>

#include <plat/gpio-cfg.h>
#include <mach/gpio-bank-e.h>
#include <mach/gpio-bank-f.h>
#include <mach/gpio-bank-k.h>

#define DEVICE_NAME     "buzzer"

#define BUZZER_IOCTL_SET_ON _IOW('Q', 0x1, int)
#define BUZZER_IOCTL_SET_OFF _IOW('Q', 0x0, int)

static void buzzer_set_on()
{
 unsigned tmp;
 tmp = readl(S3C64XX_GPFDAT);
 tmp |= 1<<14;                     //gpf14 set high level
 writel(tmp, S3C64XX_GPFDAT);

}

static void buzzer_set_off()
{
 unsigned tmp;
 
 tmp = readl(S3C64XX_GPFDAT);
 tmp &= ~(1<<14);                  //gpf14 set low level
 writel(tmp, S3C64XX_GPFDAT);

}

 

static long s3c64xx_buzzer_ioctl(struct file *filep, unsigned int cmd, long arg)
{
 switch (cmd) {
  case BUZZER_IOCTL_SET_ON:
   buzzer_set_on();
   break;
  case BUZZER_IOCTL_SET_OFF:
   buzzer_set_off();
   break;
  default:
   break;
 }
 return 0;
}

static struct file_operations dev_fops = {
    .owner   = THIS_MODULE,
    .unlocked_ioctl = s3c64xx_buzzer_ioctl,
};

static struct miscdevice misc = {
 .minor = MISC_DYNAMIC_MINOR,
 .name = DEVICE_NAME,
 .fops = &dev_fops,
};

static int __init dev_init(void)
{
 int ret;
 unsigned tmp;
 //init_MUTEX(&lock);
 tmp = readl(S3C64XX_GPFCON);
 tmp &= ~(0x3U << 28);            //set gpf14 is 00
 tmp |=  (0x1U << 28);            //set gpf14 is 01  output
 writel(tmp, S3C64XX_GPFCON);

 tmp = readl(S3C64XX_GPFPUD);
 tmp &= ~(0x3U << 28);            //gpf14 pull-up/down disable
 tmp |=  (0x2U << 28);            //gpf14 pull-up enable
 writel(tmp, S3C64XX_GPFPUD);

 tmp = readl(S3C64XX_GPFDAT);
 tmp &= ~(1<<14);                  //gpf14 set low level
 writel(tmp, S3C64XX_GPFDAT);

 ret = misc_register(&misc);

 printk (DEVICE_NAME"\tinitialized\n");
     return ret;
}

static void __exit dev_exit(void)
{
 misc_deregister(&misc);
}

module_init(dev_init);
module_exit(dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("StarFire WangYuechao");
MODULE_DESCRIPTION("S3C6410 Buzzer Driver");

转载：http://hi.baidu.com/kdwyc/blog/item/6cc28a24a5650d288744f9a6.html