kfifo: add example files to the kernel sample directory

Add four examples to the kernel sample directory.

It shows how to handle:
- a byte stream fifo
- a integer type fifo
- a dynamic record sized fifo
- the fifo DMA functions

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Stefani Seibold <stefani@seibold.net>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 163 insertions, 0 deletions

diff --git a/samples/kfifo/bytestream-example.c b/samples/kfifo/bytestream-example.c
new file mode 100644
index 000000000000..642eef3f6336
--- /dev/null
+++ b/samples/kfifo/bytestream-example.c
@@ -0,0 +1,163 @@
+/*
+ * Sample kfifo byte stream 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 byte stream fifo.
+ */
+
+/* fifo size in elements (bytes) */
+#define FIFO_SIZE       32
+
+/* name of the proc entry */
+#define PROC_FIFO       "bytestream-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
+
+#ifdef DYNAMIC
+static struct kfifo test;
+#else
+static DECLARE_KFIFO(test, unsigned char, FIFO_SIZE);
+#endif
+
+static int __init testfunc(void)
+{
+        unsigned char   buf[6];
+        unsigned char   i;
+        unsigned int    ret;
+
+        printk(KERN_INFO "byte stream fifo test start\n");
+
+        /* put string into the fifo */
+        kfifo_in(&test, "hello", 5);
+
+        /* put values into the fifo */
+        for (i = 0; i != 10; i++)
+                kfifo_put(&test, &i);
+
+        /* show the number of used elements */
+        printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
+
+        /* get max of 5 bytes from the fifo */
+        i = kfifo_out(&test, buf, 5);
+        printk(KERN_INFO "buf: %.*s\n", i, buf);
+
+        /* get max of 2 elements from the fifo */
+        ret = kfifo_out(&test, buf, 2);
+        printk(KERN_INFO "ret: %d\n", ret);
+        /* and put it back to the end of the fifo */
+        ret = kfifo_in(&test, buf, ret);
+        printk(KERN_INFO "ret: %d\n", ret);
+
+        /* put values into the fifo until is full */
+        for (i = 20; kfifo_put(&test, &i); i++)
+                ;
+
+        printk(KERN_INFO "queue len: %u\n", kfifo_len(&test));
+
+        /* print out all values in the fifo */
+        while (kfifo_get(&test, &i))
+                printk("%d ", i);
+        printk("\n");
+
+        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>");