1 /*
2 * Copyright (c) 2011-2023, Shanghai Real-Thread Electronic Technology Co.,Ltd
3 *
4 * Change Logs:
5 * Date Author Notes
6 * 2020-12-03 quanzhao the first version
7 */
8
9 #include <time.h>
10 #include <string.h>
11 #include <rtthread.h>
12
13 static struct rt_device null_dev;
14
null_read(rt_device_t dev,rt_off_t pos,void * buffer,rt_size_t size)15 static rt_ssize_t null_read (rt_device_t dev, rt_off_t pos, void *buffer, rt_size_t size)
16 {
17 return 0;
18 }
19
null_write(rt_device_t dev,rt_off_t pos,const void * buffer,rt_size_t size)20 static rt_ssize_t null_write (rt_device_t dev, rt_off_t pos, const void *buffer, rt_size_t size)
21 {
22 return size;
23 }
24
null_control(rt_device_t dev,int cmd,void * args)25 static rt_err_t null_control (rt_device_t dev, int cmd, void *args)
26 {
27 return RT_EOK;
28 }
29
30 #ifdef RT_USING_DEVICE_OPS
31 const static struct rt_device_ops null_ops =
32 {
33 RT_NULL,
34 RT_NULL,
35 RT_NULL,
36 null_read,
37 null_write,
38 null_control
39 };
40 #endif
41
null_device_init(void)42 int null_device_init(void)
43 {
44 static rt_bool_t init_ok = RT_FALSE;
45
46 if (init_ok)
47 {
48 return 0;
49 }
50 RT_ASSERT(!rt_device_find("null"));
51 null_dev.type = RT_Device_Class_Miscellaneous;
52
53 #ifdef RT_USING_DEVICE_OPS
54 null_dev.ops = &null_ops;
55 #else
56 null_dev.init = RT_NULL;
57 null_dev.open = RT_NULL;
58 null_dev.close = RT_NULL;
59 null_dev.read = null_read;
60 null_dev.write = null_write;
61 null_dev.control = null_control;
62 #endif
63
64 /* no private */
65 null_dev.user_data = RT_NULL;
66
67 rt_device_register(&null_dev, "null", RT_DEVICE_FLAG_RDWR);
68
69 init_ok = RT_TRUE;
70
71 return 0;
72 }
73 INIT_DEVICE_EXPORT(null_device_init);
74
75