kfifo: add example files to the kernel sample directory

[linux-flexiantxendom0-natty.git] / samples / kfifo / record-example.c

diff --git a/samples/kfifo/record-example.c b/samples/kfifo/record-example.c
new file mode 100644 (file)
index 0000000..32c6e0b
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+++ b/samples/kfifo/record-example.c
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+/*
+ * Sample dynamic sized record fifo implementation
+ *
+ * Copyright (C) 2010 Stefani Seibold <stefani@seibold.net>
+ *
+ * Released under the GPL version 2 only.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/mutex.h>
+#include <linux/kfifo.h>
+
+/*
+ * This module shows how to create a variable sized record fifo.
+ */
+
+/* fifo size in elements (bytes) */
+#define FIFO_SIZE      128
+
+/* name of the proc entry */
+#define        PROC_FIFO       "record-fifo"
+
+/* lock for procfs read access */
+static DEFINE_MUTEX(read_lock);
+
+/* lock for procfs write access */
+static DEFINE_MUTEX(write_lock);
+
+/*
+ * define DYNAMIC in this example for a dynamically allocated fifo.
+ *
+ * Otherwise the fifo storage will be a part of the fifo structure.
+ */
+#if 0
+#define DYNAMIC
+#endif
+
+/*
+ * struct kfifo_rec_ptr_1 and  STRUCT_KFIFO_REC_1 can handle records of a
+ * length between 0 and 255 bytes.
+ *
+ * struct kfifo_rec_ptr_2 and  STRUCT_KFIFO_REC_2 can handle records of a
+ * length between 0 and 65535 bytes.
+ */
+
+#ifdef DYNAMIC
+struct kfifo_rec_ptr_1 test;
+
+#else
+typedef STRUCT_KFIFO_REC_1(FIFO_SIZE) mytest;
+
+static mytest test;
+#endif
+
+static int __init testfunc(void)
+{
+       char            buf[100];
+       unsigned int    i;
+       unsigned int    ret;
+       struct { unsigned char buf[6]; } hello = { "hello" };
+
+       printk(KERN_INFO "record fifo test start\n");
+
+       kfifo_in(&test, &hello, sizeof(hello));
+
+       /* show the size of the next record in the fifo */
+       printk(KERN_INFO "fifo peek len: %u\n", kfifo_peek_len(&test));
+
+       /* put in variable length data */
+       for (i = 0; i < 10; i++) {
+               memset(buf, 'a' + i, i + 1);
+               kfifo_in(&test, buf, i + 1);
+       }
+
+       printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
+
+       /* show the first record without removing from the fifo */
+       ret = kfifo_out_peek(&test, buf, sizeof(buf));
+       if (ret)
+               printk(KERN_INFO "%.*s\n", ret, buf);
+
+       /* print out all records in the fifo */
+       while (!kfifo_is_empty(&test)) {
+               ret = kfifo_out(&test, buf, sizeof(buf));
+               printk(KERN_INFO "%.*s\n", ret, buf);
+       }
+
+       return 0;
+}
+
+static ssize_t fifo_write(struct file *file, const char __user *buf,
+                                               size_t count, loff_t *ppos)
+{
+       int ret;
+       unsigned int copied;
+
+       if (mutex_lock_interruptible(&write_lock))
+               return -ERESTARTSYS;
+
+       ret = kfifo_from_user(&test, buf, count, &copied);
+
+       mutex_unlock(&write_lock);
+
+       return ret ? ret : copied;
+}
+
+static ssize_t fifo_read(struct file *file, char __user *buf,
+                                               size_t count, loff_t *ppos)
+{
+       int ret;
+       unsigned int copied;
+
+       if (mutex_lock_interruptible(&read_lock))
+               return -ERESTARTSYS;
+
+       ret = kfifo_to_user(&test, buf, count, &copied);
+
+       mutex_unlock(&read_lock);
+
+       return ret ? ret : copied;
+}
+
+static const struct file_operations fifo_fops = {
+       .owner          = THIS_MODULE,
+       .read           = fifo_read,
+       .write          = fifo_write,
+};
+
+static int __init example_init(void)
+{
+#ifdef DYNAMIC
+       int ret;
+
+       ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
+       if (ret) {
+               printk(KERN_ERR "error kfifo_alloc\n");
+               return ret;
+       }
+#else
+       INIT_KFIFO(test);
+#endif
+       testfunc();
+
+       if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) {
+#ifdef DYNAMIC
+               kfifo_free(&test);
+#endif
+               return -ENOMEM;
+       }
+       return 0;
+}
+
+static void __exit example_exit(void)
+{
+       remove_proc_entry(PROC_FIFO, NULL);
+#ifdef DYNAMIC
+       kfifo_free(&test);
+#endif
+}
+
+module_init(example_init);
+module_exit(example_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");