[Linux Driver] character device driver learning Note (iii) ——— advanced

One, the IOCTL use instance

IOCTL usage examples

Driver. h file memdev.h

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1. /* Define MAGIC number */
2. #define Memdev_ioc_magic ' k '
4. /* Define the command */
5. #define Memdev_iocprint _io (memdev_ioc_magic, 1)
6. #define Memdev_iocgetdata _ior (memdev_ioc_magic, 2, int)
7. #define Memdev_iocsetdata _iow (memdev_ioc_magic, 3, int)
8. #define MEMDEV_IOC_MAXNR 3

Driver. c File

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2. /*io Operation */
4. int Memdev_ioctl (struct inode *inode, struct file *filp,
6. unsigned int cmd, unsigned long arg)
8. {
12. int err = 0;
14. int ret = 0;
16. int ioarg = 0;
20. / * Check the validity of the command * /
22. if (_ioc_type (cmd)! = memdev_ioc_magic)
24. Return-einval;
26. if (_ioc_nr (cmd) > Memdev_ioc_maxnr)
28. Return-einval;
32. / * Check whether the parameter space can be accessed according to the command type * /
34. if (_ioc_dir (cmd) & _ioc_read)
36. Err =!ACCESS_OK (Verify_write, (void *) arg, _ioc_size (cmd));
38. Else if (_ioc_dir (cmd) & _ioc_write)
40. Err =!ACCESS_OK (Verify_read, (void *) arg, _ioc_size (cmd));
42. if (err)
44. Return-efault;
48. / * Perform the appropriate action according to the command * /
50. switch (cmd) {
54. / * Print current device information * /
56. Case Memdev_iocprint:
58. PRINTK ("<---CMD memdev_iocprint done--->\n\n");
60. Break ;
64. / * Get parameters * /
66. Case Memdev_iocgetdata:
68. Ioarg = 1101;
70. ret = __put_user (Ioarg, (int *) arg);
72. Break ;
76. / * Set parameters * /
78. Case Memdev_iocsetdata:
80. ret = __get_user (Ioarg, (int *) arg);
82. PRINTK ("<---in Kernel memdev_iocsetdata ioarg =%d--->\n\n", ioarg);
84. Break ;
88. Default:
90. Return-einval;
92. }
94. return ret;
98. }

Application

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2. #include "Memdev.h"
4. cmd = Memdev_iocprint;
6. if (IOCTL (FD, CMD, &arg) < 0)
8. {
10. printf ("Call cmd memdev_iocprint fail\n");
12. return-1;
14. }
16. cmd = Memdev_iocsetdata;
18. arg = 2007;
20. if (IOCTL (FD, CMD, &arg) < 0)
22. {
24. printf ("Call cmd memdev_iocsetdata fail\n");
26. return-1;
28. }

[Linux Driver] character device driver learning Note (iii) ——— advanced