字符设备驱动之LED驱动

实现

①编写驱动框架

②编写硬件实现代码

（在Linux系统下操作硬件，需要操作虚拟地址，因此需要先把物理地址转换为虚拟地址 ioremap()）

如何实现单个灯的操作：

实现方法之一——操作次设备号

主设备号：用于查找对应的文件操作结构体；

次设备号：用于区分同类型设备下的不同设备；

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实例

driver.c

1 #include <linux/module.h>
2 #include <linux/kernel.h>
3 #include <linux/fs.h>
4 #include <linux/init.h>
5 #include <linux/delay.h>
6 #include <asm/uaccess.h>
7 #include <asm/irq.h>
8 #include <asm/io.h>
9 #include <asm/arch/regs-gpio.h>
10 #include <asm/hardware.h>
11
12 static int major;
13
14 static struct class *myLED_class;
15 static struct class_device *myLED_class_dev[4];
16
17 volatile unsigned long *gpfcon;
18 volatile unsigned long *gpfdat;
19
20 static int myLED_open(struct inode *inode, struct file *file);
21 static ssize_t myLED_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos);
22
23 static struct file_operations myLED_fops = {
24 ????????.open = myLED_open,
25 ????????.write = myLED_write,
26 ????????.owner = THIS_MODULE,
27 };
28
29 static int myLED_open(struct inode *inode, struct file *file)
30 {
31 ????????/* 初始化LED硬件 —— GPF4、GPF5、GPF6设置为输出 */
32 ????????*gpfcon &= ~((0x3<<(4*2)) | (0x3<<(5*2)) | (0x3<<(6*2)));
33 ????????*gpfcon |= (0x1<<(4*2)) | (0x1<<(5*2)) | (0x1<<(6*2));
34 ????????return 0;
35 }
36
37
38 static ssize_t myLED_write(struct file *file, const char __user *buf,
39 size_t count, loff_t *ppos)
40 {
41 ????????int val;
42 ????????int minor = MINOR(file->f_dentry->d_inode->i_rdev);????????//获取被操作设备的次设备号
43
44 ????????copy_from_user(&val, buf, count);
45 ????????switch (minor)
46 ????????{
47 ????????????????case 1:
48 ????????????????????????if (1 == val)
49 ????????????????????????{
50 ????????????????????????????????*gpfdat &= ~(1<<4);
51 ????????????????????????}
52 ????????????????????????else {
53 ????????????????????????????????*gpfdat |= 1<<4;
54 ????????????????????????}
55 ????????????????????????break;
56
57 ????????????????case 2:
58 ????????????????????????if (1 == val)
59 ????????????????????????{
60 ????????????????????????????????*gpfdat &= ~(1<<5);
61 ????????????????????????}
62 ????????????????????????else {
63 ????????????????????????????????*gpfdat |= 1<<5;
64 ????????????????????????}
65 ????????????????????????break;
66
67 ????????????????case 3:
68 ????????????????????????if (1 == val)
69 ????????????????????????{
70 ????????????????????????????????*gpfdat &= ~(1<<6);
71 ????????????????????????}
72 ????????????????????????else {
73 ????????????????????????????????*gpfdat |= 1<<6;
74 ????????????????????????}
75 ????????????????????????break;
76
77 ????????????????default:
78 ????????????????????????if (1 == val)
79 ????????????????????????{
80 ????????????????????????????????*gpfdat &= ~((1<<4) | (1<<5) | (1<<6));
81 ????????????????????????}
82 ????????????????????????else {
83 ????????????????????????????????*gpfdat |= (1<<4) | (1<<5) | (1<<6);
84 ????????????????????????}
85 ????????????????????????break;
86
87 ????????}
88 ????????return 0;
89 }
90
91 static int __init myLED_init(void)
92 {
93 ????????int minor;
94
95 ????????/* 物理地址映射成虚拟地址 */
96 ????????gpfcon = (volatile unsigned long*)ioremap(0x56000050, 16);
97 ????????gpfdat = gpfcon + 1;
98
99 ????????major = register_chrdev(0, "myLED", &myLED_fops);
100 ????????myLED_class = class_create(THIS_MODULE, "myLEDclass");
101
102 ????????/* 创建有主设备号和次设备号的设备节点系统信息 */
103 ????????myLED_class_dev[0] = class_device_create(myLED_class, NULL, MKDEV(major, 0), NULL, "LEDS");
104
105 ????????for (minor=1; minor<4; minor++)
106 ????????{
107 ????????????????myLED_class_dev[minor] = class_device_create(myLED_class, NULL, MKDEV(major, minor), NULL, "LED%d", minor);
108 ????????}
109 ????????return 0;
110 }
111
112 static void __exit myLED_exit(void)
113 {
114 ????????int minor;
115
116 ????????/* 释放虚拟地址映射 */
117 ????????iounmap(0x56000050);
118
119 ????????unregister_chrdev(major, "myLED");
120
121 ????????class_device_unregister(myLED_class_dev[0]);
122 ????????for (minor=1; minor<4; minor++)
123 ????????{
124 ????????????????myLED_class_dev[minor] = class_device_unregister(myLED_class_dev[minor]);
125 ????????}
126 ????????class_destroy(myLED_class);
127 ????????return;
128 }
129
130 module_init(myLED_init);
131 module_exit(myLED_exit);

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app.c

1 #include <sys/types.h>
2 #include <sys/stat.h>
3 #include <fcntl.h>
4 #include <stdio.h>
5
6 int main (int argc, char **argv)
7 {
8 ????????int fd;
9 ????????int val = 1;
10 ????????char *filename;
11 ????????
12 ????????printf("test app!\n");
13 ????????if (argc != 3)
14 ????????{
15 ????????????????printf("Usage: LEDx <on|off>\n");
16 ????????????????return -1;
17 ????????}
18 ????????
19 ????????filename = argv[1];
20 ????????
21 ????????fd = open(filename, O_RDWR);
22 ????????if(fd < 0)
23 ????????{
24 ????????????????printf("open failed!---%d---\n", fd);
25 ????????????????return -1;
26 ????????}
27 ????????
28 ????????if (!strcmp("on", argv[2]))
29 ????????{
30 ????????????????val = 1;
31 ????????????????write(fd, &val, 4);
32 ????????}
33 ????????else if(!strcmp("off", argv[2]))
34 ????????{????????
35 ????????????????val = 0;
36 ????????????????write(fd, &val, 4);
37 ????????}
38 ????????return 0;????????
39 }

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Makefile

1 KERN_DIR = /work/system/linux-2.6.22.6
2
3 all:
4 ????????make -C $(KERN_DIR) M=`pwd` modules
5
6 clean:
7 ????????make -C $(KERN_DIR) M=`pwd` modules clean
8 ????????rm -rf modules.order
9
10 obj-m += myLED.o