inttype-example.c 3.7 KB

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  1. // SPDX-License-Identifier: GPL-2.0-only
  2. /*
  3. * Sample kfifo int type implementation
  4. *
  5. * Copyright (C) 2010 Stefani Seibold <stefani@seibold.net>
  6. */
  7. #include <linux/init.h>
  8. #include <linux/module.h>
  9. #include <linux/proc_fs.h>
  10. #include <linux/mutex.h>
  11. #include <linux/kfifo.h>
  12. /*
  13. * This module shows how to create a int type fifo.
  14. */
  15. /* fifo size in elements (ints) */
  16. #define FIFO_SIZE 32
  17. /* name of the proc entry */
  18. #define PROC_FIFO "int-fifo"
  19. /* lock for procfs read access */
  20. static DEFINE_MUTEX(read_lock);
  21. /* lock for procfs write access */
  22. static DEFINE_MUTEX(write_lock);
  23. /*
  24. * define DYNAMIC in this example for a dynamically allocated fifo.
  25. *
  26. * Otherwise the fifo storage will be a part of the fifo structure.
  27. */
  28. #if 0
  29. #define DYNAMIC
  30. #endif
  31. #ifdef DYNAMIC
  32. static DECLARE_KFIFO_PTR(test, int);
  33. #else
  34. static DEFINE_KFIFO(test, int, FIFO_SIZE);
  35. #endif
  36. static const int expected_result[FIFO_SIZE] = {
  37. 3, 4, 5, 6, 7, 8, 9, 0,
  38. 1, 20, 21, 22, 23, 24, 25, 26,
  39. 27, 28, 29, 30, 31, 32, 33, 34,
  40. 35, 36, 37, 38, 39, 40, 41, 42,
  41. };
  42. static int __init testfunc(void)
  43. {
  44. int buf[6];
  45. int i, j;
  46. unsigned int ret;
  47. printk(KERN_INFO "int fifo test start\n");
  48. /* put values into the fifo */
  49. for (i = 0; i != 10; i++)
  50. kfifo_put(&test, i);
  51. /* show the number of used elements */
  52. printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
  53. /* get max of 2 elements from the fifo */
  54. ret = kfifo_out(&test, buf, 2);
  55. printk(KERN_INFO "ret: %d\n", ret);
  56. /* and put it back to the end of the fifo */
  57. ret = kfifo_in(&test, buf, ret);
  58. printk(KERN_INFO "ret: %d\n", ret);
  59. /* skip first element of the fifo */
  60. printk(KERN_INFO "skip 1st element\n");
  61. kfifo_skip(&test);
  62. /* put values into the fifo until is full */
  63. for (i = 20; kfifo_put(&test, i); i++)
  64. ;
  65. printk(KERN_INFO "queue len: %u\n", kfifo_len(&test));
  66. /* show the first value without removing from the fifo */
  67. if (kfifo_peek(&test, &i))
  68. printk(KERN_INFO "%d\n", i);
  69. /* check the correctness of all values in the fifo */
  70. j = 0;
  71. while (kfifo_get(&test, &i)) {
  72. printk(KERN_INFO "item = %d\n", i);
  73. if (i != expected_result[j++]) {
  74. printk(KERN_WARNING "value mismatch: test failed\n");
  75. return -EIO;
  76. }
  77. }
  78. if (j != ARRAY_SIZE(expected_result)) {
  79. printk(KERN_WARNING "size mismatch: test failed\n");
  80. return -EIO;
  81. }
  82. printk(KERN_INFO "test passed\n");
  83. return 0;
  84. }
  85. static ssize_t fifo_write(struct file *file, const char __user *buf,
  86. size_t count, loff_t *ppos)
  87. {
  88. int ret;
  89. unsigned int copied;
  90. if (mutex_lock_interruptible(&write_lock))
  91. return -ERESTARTSYS;
  92. ret = kfifo_from_user(&test, buf, count, &copied);
  93. mutex_unlock(&write_lock);
  94. if (ret)
  95. return ret;
  96. return copied;
  97. }
  98. static ssize_t fifo_read(struct file *file, char __user *buf,
  99. size_t count, loff_t *ppos)
  100. {
  101. int ret;
  102. unsigned int copied;
  103. if (mutex_lock_interruptible(&read_lock))
  104. return -ERESTARTSYS;
  105. ret = kfifo_to_user(&test, buf, count, &copied);
  106. mutex_unlock(&read_lock);
  107. if (ret)
  108. return ret;
  109. return copied;
  110. }
  111. static const struct proc_ops fifo_proc_ops = {
  112. .proc_read = fifo_read,
  113. .proc_write = fifo_write,
  114. .proc_lseek = noop_llseek,
  115. };
  116. static int __init example_init(void)
  117. {
  118. #ifdef DYNAMIC
  119. int ret;
  120. ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
  121. if (ret) {
  122. printk(KERN_ERR "error kfifo_alloc\n");
  123. return ret;
  124. }
  125. #endif
  126. if (testfunc() < 0) {
  127. #ifdef DYNAMIC
  128. kfifo_free(&test);
  129. #endif
  130. return -EIO;
  131. }
  132. if (proc_create(PROC_FIFO, 0, NULL, &fifo_proc_ops) == NULL) {
  133. #ifdef DYNAMIC
  134. kfifo_free(&test);
  135. #endif
  136. return -ENOMEM;
  137. }
  138. return 0;
  139. }
  140. static void __exit example_exit(void)
  141. {
  142. remove_proc_entry(PROC_FIFO, NULL);
  143. #ifdef DYNAMIC
  144. kfifo_free(&test);
  145. #endif
  146. }
  147. module_init(example_init);
  148. module_exit(example_exit);
  149. MODULE_LICENSE("GPL");
  150. MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");