Article Directory
1 Modify the device tree file
The device tree file can directly use the gpioled sub-nodes added in Chapter 35, without repeating additions.
2 platform driver
The path of the experiment routine: i.MX6UL Terminator CD-ROM data/06_Linux driver routine/15_gpioled_dts to
create the led_driver.c file, the specific content is as follows:
1 #include <linux/types.h>
2 #include <linux/kernel.h>
3 #include <linux/delay.h>
4 #include <linux/ide.h>
5 #include <linux/init.h>
6 #include <linux/module.h>
7 #include <linux/errno.h>
8 #include <linux/gpio.h>
9 #include <linux/cdev.h>
10 #include <linux/device.h>
11 #include <linux/of_gpio.h>
12 #include <linux/semaphore.h>
13 #include <linux/timer.h>
14 #include <linux/irq.h>
15 #include <linux/wait.h>
16 #include <linux/poll.h>
17 #include <linux/fs.h>
18 #include <linux/fcntl.h>
19 #include <linux/platform_device.h>
20 #include <asm/mach/map.h>
21 #include <asm/uaccess.h>
22 #include <asm/io.h>
23
24 #define LEDDEV_CNT 1 /* 设备号长度 */
25 #define LEDDEV_NAME "dtsplatled" /* 设备名字 */
26 #define LEDOFF 0
27 #define LEDON 1
28
29 /* leddev设备结构体 */
30 struct leddev_dev{
31 dev_t devid; /* 设备号 */
32 struct cdev cdev; /* cdev */
33 struct class *class; /* 类 */
34 struct device *device; /* 设备 */
35 int major; /* 主设备号 */
36 struct device_node *node; /* LED设备节点 */
37 int led0; /* LED灯GPIO标号 */
38 };
39
40 struct leddev_dev leddev; /* led设备 */
41
42 /*
43 * @description : LED打开/关闭
44 * @param - sta : LEDON(0) 打开LED，LEDOFF(1) 关闭LED
45 * @return : 无
46 */
47 void led0_switch(u8 sta)
48 {
49 if (sta == LEDON )
50 gpio_set_value(leddev.led0, 0);
51 else if (sta == LEDOFF)
52 gpio_set_value(leddev.led0, 1);
53 }
54
55 /*
56 * @description : 打开设备
57 * @param - inode : 传递给驱动的inode
58 * @param - filp : 设备文件，file结构体有个叫做private_data的成员变量
59 * 一般在open的时候将private_data指向设备结构体。
60 * @return : 0 成功;其他 失败
61 */
62 static int led_open(struct inode *inode, struct file *filp)
63 {
64 filp->private_data = &leddev; /* 设置私有数据 */
65 return 0;
66 }
67
68 /*
69 * @description : 向设备写数据
70 * @param - filp : 设备文件，表示打开的文件描述符
71 * @param - buf : 要写给设备写入的数据
72 * @param - cnt : 要写入的数据长度
73 * @param - offt : 相对于文件首地址的偏移
74 * @return : 写入的字节数，如果为负值，表示写入失败
75 */
76 static ssize_t led_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offt)
77 {
78 int retvalue;
79 unsigned char databuf[2];
80 unsigned char ledstat;
81
82 retvalue = copy_from_user(databuf, buf, cnt);
83 if(retvalue < 0) {
84
85 printk("kernel write failed!\r\n");
86 return -EFAULT;
87 }
88
89 ledstat = databuf[0];
90 if (ledstat == LEDON) {
91 led0_switch(LEDON);
92 } else if (ledstat == LEDOFF) {
93 led0_switch(LEDOFF);
94 }
95 return 0;
96 }
97
98 /* 设备操作函数 */
99 static struct file_operations led_fops = {
100 .owner = THIS_MODULE,
101 .open = led_open,
102 .write = led_write,
103 };
104
105 /*
106 * @description : flatform驱动的probe函数，当驱动与
107 * 设备匹配以后此函数就会执行
108 * @param - dev : platform设备
109 * @return : 0，成功;其他负值,失败
110 */
111 static int led_probe(struct platform_device *dev)
112 {
113 printk("led driver and device was matched!\r\n");
114 /* 1、设置设备号 */
115 if (leddev.major) {
116 leddev.devid = MKDEV(leddev.major, 0);
117 register_chrdev_region(leddev.devid, LEDDEV_CNT, LEDDEV_NAME);
118 } else {
119 alloc_chrdev_region(&leddev.devid, 0, LEDDEV_CNT, LEDDEV_NAME);
120 leddev.major = MAJOR(leddev.devid);
121 }
122
123 /* 2、注册设备 */
124 cdev_init(&leddev.cdev, &led_fops);
125 cdev_add(&leddev.cdev, leddev.devid, LEDDEV_CNT);
126
127 /* 3、创建类 */
128 leddev.class = class_create(THIS_MODULE, LEDDEV_NAME);
129 if (IS_ERR(leddev.class)) {
130 return PTR_ERR(leddev.class);
131 }
132
133 /* 4、创建设备 */
134 leddev.device = device_create(leddev.class, NULL, leddev.devid,
NULL, LEDDEV_NAME);
135 if (IS_ERR(leddev.device)) {
136 return PTR_ERR(leddev.device);
137 }
138
139 /* 5、初始化IO */
140 leddev.node = of_find_node_by_path("/gpioled");
141 if (leddev.node == NULL){
142 printk("gpioled node nost find!\r\n");
143 return -EINVAL;
144 }
145
146 leddev.led0 = of_get_named_gpio(leddev.node, "led-gpio", 0);
147 if (leddev.led0 < 0) {
148 printk("can't get led-gpio\r\n");
149 return -EINVAL;
150 }
151
152 gpio_request(leddev.led0, "led0");
153 gpio_direction_output(leddev.led0, 1); /* led0 IO设置为输出，默认高电平 */
154 return 0;
155 }
156
157 /*
158 * @description : platform驱动的remove函数，移除platform
驱动的时候此函数会执行
159 * @param - dev : platform设备
160 * @return : 0，成功;其他负值,失败
161 */
162 static int led_remove(struct platform_device *dev)
163 {
164 gpio_set_value(leddev.led0, 1); /* 卸载驱动的时候关闭LED */
165
166 cdev_del(&leddev.cdev); /* 删除cdev */
167 unregister_chrdev_region(leddev.devid, LEDDEV_CNT); /* 注销设备号 */
168 device_destroy(leddev.class, leddev.devid);
169 class_destroy(leddev.class);
170 return 0;
171 }
172
173 /* 匹配列表 */
174 static const struct of_device_id led_of_match[] = {
175 {
.compatible = "gpioled" },
176 {
/* Sentinel */ }
177 };
178
179 /* platform驱动结构体 */
180 static struct platform_driver led_driver = {
181 .driver = {
182 .name = "imx6ul-led", /* 驱动名字，用于和设备匹配 */
183 .of_match_table = led_of_match, /* 设备树匹配表 */
184 },
185 .probe = led_probe,
186 .remove = led_remove,
187 };
188
189 /*
190 * @description : 驱动模块加载函数
191 * @param : 无
192 * @return : 无
193 */
194 static int __init leddriver_init(void)
195 {
196 return platform_driver_register(&led_driver);
197 }
198
199 /*
200 * @description : 驱动模块卸载函数
201 * @param : 无
202 * @return : 无
203 */
204 static void __exit leddriver_exit(void)
205 {
206 platform_driver_unregister(&led_driver);
207 }
208
209 module_init(leddriver_init);
210 module_exit(leddriver_exit);
211 MODULE_LICENSE("GPL");
212 MODULE_AUTHOR("topeet");
Lines 174~177, the matching table, describe what kind of device the driver matches. Line 175 adds a compatible attribute value of "gpioled". When the compatible attribute value of a device node in the device tree is also When it is "gpioled", it will match this driver.
Lines 180~187, platform_driver driver structure, line 182 sets the name of this platform driver to "imx6ul-led", so when the driver is loaded successfully, there will be a name in the /sys/bus/platform/drivers/ directory The file is "imx6u-led". Line 183 sets of_match_table to led_of_match above.
3 Application test program
The application test program can directly use led_test.c in 44.3.2 of the previous chapter.
