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, 115 insertions, 0 deletions

diff --git a/samples/kfifo/dma-example.c b/samples/kfifo/dma-example.c
new file mode 100644
index 000000000000..b9482c28b41a
--- /dev/null
+++ b/samples/kfifo/dma-example.c
@@ -0,0 +1,115 @@
+/*
+ * Sample fifo dma 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/kfifo.h>
+
+/*
+ * This module shows how to handle fifo dma operations.
+ */
+
+/* fifo size in elements (bytes) */
+#define FIFO_SIZE       32
+
+static struct kfifo fifo;
+
+static int __init example_init(void)
+{
+        int                     i;
+        unsigned int            ret;
+        struct scatterlist      sg[10];
+
+        printk(KERN_INFO "DMA fifo test start\n");
+
+        if (kfifo_alloc(&fifo, FIFO_SIZE, GFP_KERNEL)) {
+                printk(KERN_ERR "error kfifo_alloc\n");
+                return 1;
+        }
+
+        printk(KERN_INFO "queue size: %u\n", kfifo_size(&fifo));
+
+        kfifo_in(&fifo, "test", 4);
+
+        for (i = 0; i != 9; i++)
+                kfifo_put(&fifo, &i);
+
+        /* kick away first byte */
+        ret = kfifo_get(&fifo, &i);
+
+        printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));
+
+        ret = kfifo_dma_in_prepare(&fifo, sg, ARRAY_SIZE(sg), FIFO_SIZE);
+        printk(KERN_INFO "DMA sgl entries: %d\n", ret);
+
+        /* if 0 was returned, fifo is full and no sgl was created */
+        if (ret) {
+                printk(KERN_INFO "scatterlist for receive:\n");
+                for (i = 0; i < ARRAY_SIZE(sg); i++) {
+                        printk(KERN_INFO
+                        "sg[%d] -> "
+                        "page_link 0x%.8lx offset 0x%.8x length 0x%.8x\n",
+                                i, sg[i].page_link, sg[i].offset, sg[i].length);
+
+                        if (sg_is_last(&sg[i]))
+                                break;
+                }
+
+                /* but here your code to setup and exectute the dma operation */
+                /* ... */
+
+                /* example: zero bytes received */
+                ret = 0;
+
+                /* finish the dma operation and update the received data */
+                kfifo_dma_in_finish(&fifo, ret);
+        }
+
+        ret = kfifo_dma_out_prepare(&fifo, sg, ARRAY_SIZE(sg), 8);
+        printk(KERN_INFO "DMA sgl entries: %d\n", ret);
+
+        /* if 0 was returned, no data was available and no sgl was created */
+        if (ret) {
+                printk(KERN_INFO "scatterlist for transmit:\n");
+                for (i = 0; i < ARRAY_SIZE(sg); i++) {
+                        printk(KERN_INFO
+                        "sg[%d] -> "
+                        "page_link 0x%.8lx offset 0x%.8x length 0x%.8x\n",
+                                i, sg[i].page_link, sg[i].offset, sg[i].length);
+
+                        if (sg_is_last(&sg[i]))
+                                break;
+                }
+
+                /* but here your code to setup and exectute the dma operation */
+                /* ... */
+
+                /* example: 5 bytes transmitted */
+                ret = 5;
+
+                /* finish the dma operation and update the transmitted data */
+                kfifo_dma_out_finish(&fifo, ret);
+        }
+
+        printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));
+
+        return 0;
+}
+
+static void __exit example_exit(void)
+{
+#ifdef DYNAMIC
+        kfifo_free(&test);
+#endif
+}
+
+module_init(example_init);
+module_exit(example_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");