Linux 字符设备驱动开发基础（二）—— 编写简单 PWM 设备驱动
编写驱动的第一步仍是看原理图：
可以看到，该蜂鸣器由 GPD0_0 来控制 ，查手册可知该I/O口由Time0 来控制，找到相应的寄存器：
a -- I/O口寄存器及地址
GPD0CON 0x114000a0
b -- Time0 寄存器及地址
基地址为：TIMER_BASE 0x139D0000
这些物理寄存器地址都是相邻的，我们这里用偏移量来表示：
寄存器名 地址偏移量 所需配置
TCFG0 0x0000 [7-0] 0XFF
TCFG1 0x0004 [3-0] 0X2
TCON 0x0008 [3-0] 0X2 0X9 0X0
TCNTB0 0x000C 500
TCMPB0 0x0010 250
前面已经知道，驱动是无法直接操纵物理地址的，所以这里仍需物理地址向虚拟地址的转换，用到 ioremap() 函数、writel()函数、readl()函数：
1、地址映射操作
unsigned int *gpd0con; void *timer_base;<span style="white-space:pre"> </span>//之所以是void类型，偏移量为4时，只是移动4个字节，方便理解 gpd0con = ioremap(GPD0CON,4); timer_base = ioremap(TIMER_BASE , 0x14);
2、Time0初始化操作（这里使用的已经是虚拟地址）
这里现将数据从寄存器中读出，修改后再写回寄存器，具体寄存器操作可以移步Exynos4412裸机开发——PWM定时器:
writel((readl(gpd0con)&~(0xf<<0)) | (0x2<<0),gpd0con); writel ((readl(timer_base +TCFG0 )&~(0xff<<0)) | (0xff <<0),timer_base +TCFG0); writel ((readl(timer_base +TCFG1 )&~(0xf<<0)) | (0x2 <<0),timer_base +TCFG1 );
3、装载数据，配置占空比
writel(500, timer_base +TCNTB0 ); writel(250, timer_base +TCMPB0 ); writel ((readl(timer_base +TCON )&~(0xf<<0)) | (0x2 <<0),timer_base +TCON );
4、相关控制函数
void beep_on(void)
{
writel ((readl(timer_base +TCON )&~(0xf<<0)) | (0x9 <<0),timer_base +TCON );
}
void beep_off(void)
{
writel ((readl(timer_base +TCON )&~(0xf<<0)) | (0x0 <<0),timer_base +TCON );
}
下面是驱动程序，这里我们用到了 write() read() ioctl() 函数，具体解析移步：
驱动程序:beep.c
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <asm/io.h>
#include <asm/uaccess.h>
static int major = 250;
static int minor=0;
static dev_t devno;
static struct class *cls;
static struct device *test_device;
#define GPD0CON 0x114000a0
#define TIMER_BASE 0x139D0000
#define TCFG0 0x0000
#define TCFG1 0x0004
#define TCON 0x0008
#define TCNTB0 0x000C
#define TCMPB0 0x0010
static unsigned int *gpd0con;
static void *timer_base;
#define MAGIC_NUMBER 'k'
#define BEEP_ON _IO(MAGIC_NUMBER ,0)
#define BEEP_OFF _IO(MAGIC_NUMBER ,1)
#define BEEP_FREQ _IO(MAGIC_NUMBER ,2)
static void fs4412_beep_init(void)
{
gpd0con = ioremap(GPD0CON,4);
timer_base = ioremap(TIMER_BASE,0x14);
writel ((readl(gpd0con)&~(0xf<<0)) | (0x2<<0),gpd0con);
writel ((readl(timer_base +TCFG0 )&~(0xff<<0)) | (0xff <<0),timer_base +TCFG0);
writel ((readl(timer_base +TCFG1 )&~(0xf<<0)) | (0x2 <<0),timer_base +TCFG1 );
writel (500, timer_base +TCNTB0 );
writel (250, timer_base +TCMPB0 );
writel ((readl(timer_base +TCON )&~(0xf<<0)) | (0x2 <<0),timer_base +TCON );
}
void fs4412_beep_on(void)
{
writel ((readl(timer_base +TCON )&~(0xf<<0)) | (0x9 <<0),timer_base +TCON );
}
void fs4412_beep_off(void)
{
writel ((readl(timer_base +TCON )&~(0xf<<0)) | (0x0 <<0),timer_base +TCON );
}
static int beep_open (struct inode *inode, struct file *filep)
{
// fs4412_beep_on();
return 0;
}
static int beep_release(struct inode *inode, struct file *filep)
{
fs4412_beep_off();
return 0;
}
#define BEPP_IN_FREQ 100000
static void beep_freq(unsigned long arg)
{
writel(BEPP_IN_FREQ/arg, timer_base +TCNTB0 );
writel(BEPP_IN_FREQ/(2*arg), timer_base +TCMPB0 );
}
static long beep_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
{
switch(cmd)
{
case BEEP_ON:
fs4412_beep_on();
break;
case BEEP_OFF:
fs4412_beep_off();
break;
case BEEP_FREQ:
beep_freq( arg );
break;
default :
return -EINVAL;
}
}
static struct file_operations beep_ops=
{
.open = beep_open,
.release = beep_release,
.unlocked_ioctl = beep_ioctl,
};
static int beep_init(void)
{
int ret;
devno = MKDEV(major,minor);
ret = register_chrdev(major,"beep",&beep_ops);
cls = class_create(THIS_MODULE, "myclass");
if(IS_ERR(cls))
{
unregister_chrdev(major,"beep");
return -EBUSY;
}
test_device = device_create(cls,NULL,devno,NULL,"beep");//mknod /dev/hello
if(IS_ERR(test_device))
{
class_destroy(cls);
unregister_chrdev(major,"beep");
return -EBUSY;
}
fs4412_beep_init();
return 0;
}
void fs4412_beep_unmap(void)
{
iounmap(gpd0con);
iounmap(timer_base);
}
static void beep_exit(void)
{
fs4412_beep_unmap();
device_destroy(cls,devno);
class_destroy(cls);
unregister_chrdev(major,"beep");
printk("beep_exit \n");
}
MODULE_LICENSE("GPL");
module_init(beep_init);
module_exit(beep_exit);
makefile:
ifneq ($(KERNELRELEASE),) obj-m:=beep.o $(info "2nd") else #KDIR := /lib/modules/$(shell uname -r)/build KDIR := /home/fs/linux/linux-3.14-fs4412 PWD:=$(shell pwd) all: $(info "1st") make -C $(KDIR) M=$(PWD) modules arm-none-linux-gnueabi-gcc test.c -o beeptest sudo cp beep.ko beeptest /tftpboot clean: rm -f *.ko *.o *.symvers *.mod.c *.mod.o *.order endif
下面是是个简单的测试程序test.c，仅实现蜂鸣器响6秒的功能：
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/ioctl.h>
#define MAGIC_NUMBER 'k'
#define BEEP_ON _IO(MAGIC_NUMBER ,0)
#define BEEP_OFF _IO(MAGIC_NUMBER ,1)
#define BEEP_FREQ _IO(MAGIC_NUMBER ,2)
main()
{
int fd;
fd = open("/dev/beep",O_RDWR);
if(fd<0)
{
perror("open fail \n");
return ;
}
ioctl(fd,BEEP_ON);
sleep(6);
ioctl(fd,BEEP_OFF);
close(fd);
}
这是个音乐播放测试程序，慎听！！分别为《大长今》、《世上只有妈妈好》、《渔船》，这个单独编译一下
/*
* main.c : test demo driver
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include "pwm_music.h"
/*ioctl 鍛戒护*/
#define magic_number 'k'
#define BEEP_ON _IO(magic_number,0)
#define BEEP_OFF _IO(magic_number,1)
#define SET_FRE _IO(magic_number,2)
int main(void)
{
int i = 0;
int n = 2;
int dev_fd;
int div;
dev_fd = open("/dev/beep",O_RDWR | O_NONBLOCK);
if ( dev_fd == -1 ) {
perror("open");
exit(1);
}
for(i = 0;i<sizeof(GreatlyLongNow)/sizeof(Note);i++ )
{
div = (GreatlyLongNow[i].pitch);
ioctl(dev_fd, SET_FRE, div);
ioctl(dev_fd, BEEP_ON);
usleep(GreatlyLongNow[i].dimation * 100);
ioctl(dev_fd, BEEP_OFF);
}
for(i = 0;i<sizeof(MumIsTheBestInTheWorld)/sizeof(Note);i++ )
{
div = (MumIsTheBestInTheWorld[i].pitch);
ioctl(dev_fd, SET_FRE, div);
ioctl(dev_fd, BEEP_ON);
usleep(MumIsTheBestInTheWorld[i].dimation * 100);
ioctl(dev_fd, BEEP_OFF);
}
for(i = 0;i<sizeof(FishBoat)/sizeof(Note);i++ )
{
div = (FishBoat[i].pitch);
ioctl(dev_fd, SET_FRE, div);
ioctl(dev_fd, BEEP_ON);
usleep(FishBoat[i].dimation * 100);
ioctl(dev_fd, BEEP_OFF);
}
return 0;
}
附所用头文件：
#ifndef __PWM_MUSIC_H
#define __PWM_MUSIC_H
#define BIG_D
#define PCLK (202800000/4)
typedef struct
{
int pitch;
int dimation;
}Note;
// 1 2 3 4 5 6 7
// C D E F G A B
//261.6256 293.6648 329.6276 349.2282 391.9954 440 493.8833
//C澶ц皟
#ifdef BIG_C
#define DO 262
#define RE 294
#define MI 330
#define FA 349
#define SOL 392
#define LA 440
#define SI 494
#define TIME 6000
#endif
//D澶ц皟
#ifdef BIG_D
#define DO 293
#define RE 330
#define MI 370
#define FA 349
#define SOL 440
#define LA 494
#define SI 554
#define TIME 6000
#endif
Note MumIsTheBestInTheWorld[]={
//6. //_5 //3 //5
{LA,TIME+TIME/2}, {SOL,TIME/2},{MI,TIME},{SOL,TIME},
//1^ //6_ //_5 //6-
{DO*2,TIME},{LA,TIME/2},{SOL,TIME/2} ,{LA,2*TIME},
// 3 //5_ //_6 //5
{MI,TIME},{SOL,TIME/2},{LA,TIME/2},{SOL,TIME},
// 3 //1_ //_6,
{MI,TIME},{DO,TIME/2},{LA/2,TIME/2},
//5_ //_3 //2- //2.
{SOL,TIME/2},{MI,TIME/2},{RE,TIME*2},{RE,TIME+TIME/2},
//_3 //5 //5_ //_6
{MI,TIME/2},{SOL,TIME},{SOL,TIME/2},{LA,TIME/2},
// 3 //2 //1- //5.
{MI,TIME},{RE,TIME},{DO,TIME*2},{SOL,TIME+TIME/2},
//_3 //2_ //_1 //6,_
{MI,TIME/2},{RE,TIME/2},{DO,TIME/2},{LA/2,TIME/2},
//_1 //5,--
{DO,TIME/2},{SOL/2,TIME*3}
};
Note GreatlyLongNow[]={
// 2 3 3 3. _2 1
{RE,TIME}, {MI,TIME},{MI,TIME},{MI,TIME+TIME/2},{RE,TIME/2},{DO,TIME},
//6, 1 2 1-- 2 3 3
{LA/2,TIME},{DO,TIME},{RE,TIME},{DO,TIME*3},{RE,TIME},{MI,TIME},{MI,TIME},
//3. _5 3 3 2 3
{MI,TIME+TIME/2},{SOL,TIME/2},{MI,TIME},{MI,TIME},{RE,TIME},{MI,TIME},
//3-- 5 6 6 6. _5
{MI,TIME*3},{SOL,TIME},{LA,TIME},{LA,TIME},{LA,TIME+TIME/2},{SOL,TIME/2},
// 3 3 5 6 5--- 2 3
{MI,TIME},{MI,TIME},{SOL,TIME},{LA,TIME},{SOL,TIME*3},{RE,TIME},{MI,TIME},
// 3 2. _3 3 2 3
{MI,TIME},{RE,TIME+TIME/2},{MI,TIME/2},{MI,TIME},{RE,TIME},{MI,TIME},
//6, 1_ _6, 6,-
{LA/2,TIME},{DO,TIME/2},{LA/2,TIME/2},{LA/2,TIME*2},
//2_ _2 2_ _1 6,
{RE,TIME/2},{RE,TIME/2},{RE,TIME/2},{DO,TIME/2},{LA/2,TIME},
//2_ _2 2_ _1 6,
{RE,TIME/2},{RE,TIME/2},{RE,TIME/2},{DO,TIME/2},{LA/2,TIME},
// 2 3 1 2. _3 5
{RE,TIME},{MI,TIME},{DO,TIME},{RE,TIME+TIME/2},{MI,TIME/2},{SOL,TIME},
//6_ _6 6_ _5 3
{LA,TIME/2},{LA,TIME/2},{LA,TIME/2},{SOL,TIME/2},{MI,TIME},
//2_ _2 2_ _1 6,
{RE,TIME/2},{RE,TIME/2},{RE,TIME/2},{DO,TIME/2},{LA/2,TIME},
//6, 5,. _6, 6,--
{LA/2,TIME},{SOL/2,TIME+TIME/2},{LA/2,TIME/2},{LA/2,TIME*3},
//2_ _2 2_ _1 6,
{RE,TIME/2},{RE,TIME/2},{RE,TIME/2},{DO,TIME/2},{LA/2,TIME},
//2_ _2 2_ _1 6,
{RE,TIME/2},{RE,TIME/2},{RE,TIME/2},{DO,TIME/2},{LA/2,TIME},
// 2 3 1 2. _3 5
{RE,TIME},{MI,TIME},{DO,TIME},{RE,TIME+TIME/2},{MI,TIME/2},{SOL,TIME},
//6_ _6 6_ _5 3
{LA,TIME/2},{LA,TIME/2},{LA,TIME/2},{SOL,TIME/2},{MI,TIME},
//2_ _2 2_ _1 6,
{RE,TIME/2},{RE,TIME/2},{RE,TIME/2},{DO,TIME/2},{LA/2,TIME},
//6, 5,. _6, 6,--
{LA/2,TIME},{SOL/2,TIME+TIME/2},{LA/2,TIME/2},{LA/2,TIME*3}
};
Note FishBoat[]={ //3. _5 6._ =1^ 6_
{MI,TIME+TIME/2},{SOL,TIME/2},{LA,TIME/2+TIME/4},{DO*2,TIME/4},{LA,TIME/2},
//_5 3 -. 2 1. _3 2._
{SOL,TIME/2},{MI,TIME*3},{RE,TIME},{DO,TIME+TIME/2},{MI,TIME/2},{RE,TIME/2+TIME/4},
//=3 2_ _1 2-- 3. _5
{MI,TIME/4},{RE,TIME/2},{DO,TIME/2},{RE,TIME*4},{MI,TIME+TIME/2},{SOL,TIME/2},
// 2 1 6._ =1^ 6_ _5
{RE,TIME},{DO,TIME},{LA,TIME/2+TIME/4},{DO*2,TIME/4},{LA,TIME/2},{SOL,TIME/2},
//6- 5,. _6, 1._ =3
{LA,TIME*2},{SOL/2,TIME+TIME/2},{LA/2,TIME/2},{DO,TIME/2+TIME/4},{MI,TIME/4},
//2_ _1 5,--
{RE,TIME/2},{DO,TIME/2},{SOL/2,TIME*4},
//3. _5 6._ =1^ 6_
{MI,TIME+TIME/2},{SOL,TIME/2},{LA,TIME/2+TIME/4},{DO*2,TIME/4},{LA,TIME/2},
//_5 3-. 5_ _6 1^_ _6
{SOL,TIME/2},{MI,TIME*3},{SOL,TIME/2},{LA,TIME/2},{DO*2,TIME+TIME/2},{LA,TIME/2},
//5._ =6 5_ _3 2--
{SOL,TIME/2+TIME/4},{LA,TIME/4},{SOL,TIME/2},{MI,TIME/2},{RE,TIME*4},
//3. _5 2._ =3 2_ _1
{MI,TIME+TIME/2},{SOL,TIME/2},{RE,TIME/2+TIME/4},{MI,TIME/4},{RE,TIME/2},{DO,TIME/2},
//6._ =1^ 6_ _5 6- 1.
{LA,TIME/2+TIME/4},{DO*2,TIME/4},{LA,TIME/2},{SOL,TIME/2},{LA,TIME*2},{DO,TIME+TIME/2},
//_2 3_ _5 2_ _3 1--
{RE,TIME/2},{MI,TIME/2},{SOL,TIME/2},{RE,TIME/2},{MI,TIME/2},{DO,TIME*4}
};
#endif
# insmod beep.ko
#mknod /dev/beep c 250 0
#./music
便会听到悦耳的音乐了！