kfifo: add explicit error checking in all the examples

Provide a check in all the kfifo examples to validate the correct
execution of each testcase.

Signed-off-by: Andrea Righi <arighi@develer.com>
Acked-by: Stefani Seibold <stefani@seibold.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 67 insertions, 39 deletions

diff --git a/samples/kfifo/dma-example.c b/samples/kfifo/dma-example.c
index 3682278785f..ee03a4f0b64 100644
--- a/samples/kfifo/dma-example.c
+++ b/samples/kfifo/dma-example.c
@@ -29,8 +29,8 @@ static int __init example_init(void)
 	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_WARNING "error kfifo_alloc\n");
+		return -ENOMEM;
 	}
 
 	printk(KERN_INFO "queue size: %u\n", kfifo_size(&fifo));
@@ -41,65 +41,93 @@ static int __init example_init(void)
 		kfifo_put(&fifo, &i);
 
 	/* kick away first byte */
-	ret = kfifo_get(&fifo, &i);
+	kfifo_skip(&fifo);
 
 	printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));
 
+	/*
+	 * Configure the kfifo buffer to receive data from DMA input.
+	 *
+	 *  .--------------------------------------.
+	 *  | 0 | 1 | 2 | ... | 12 | 13 | ... | 31 |
+	 *  |---|------------------|---------------|
+	 *   \_/ \________________/ \_____________/
+	 *    \          \                  \
+	 *     \          \_allocated data   \
+	 *      \_*free space*                \_*free space*
+	 *
+	 * We need two different SG entries: one for the free space area at the
+	 * end of the kfifo buffer (19 bytes) and another for the first free
+	 * byte at the beginning, after the kfifo_skip().
+	 */
 	sg_init_table(sg, ARRAY_SIZE(sg));
 	ret = kfifo_dma_in_prepare(&fifo, sg, ARRAY_SIZE(sg), FIFO_SIZE);
 	printk(KERN_INFO "DMA sgl entries: %d\n", ret);
+	if (!ret) {
+		/* fifo is full and no sgl was created */
+		printk(KERN_WARNING "error kfifo_dma_in_prepare\n");
+		return -EIO;
+	}
 
-	/* 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);
+	/* receive data */
+	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;
-		}
+		if (sg_is_last(&sg[i]))
+			break;
+	}
 
-		/* but here your code to setup and exectute the dma operation */
-		/* ... */
+	/* put here your code to setup and exectute the dma operation */
+	/* ... */
 
-		/* example: zero bytes received */
-		ret = 0;
+	/* example: zero bytes received */
+	ret = 0;
 
-		/* finish the dma operation and update the received data */
-		kfifo_dma_in_finish(&fifo, ret);
-	}
+	/* finish the dma operation and update the received data */
+	kfifo_dma_in_finish(&fifo, ret);
 
+	/* Prepare to transmit data, example: 8 bytes */
 	ret = kfifo_dma_out_prepare(&fifo, sg, ARRAY_SIZE(sg), 8);
 	printk(KERN_INFO "DMA sgl entries: %d\n", ret);
+	if (!ret) {
+		/* no data was available and no sgl was created */
+		printk(KERN_WARNING "error kfifo_dma_out_prepare\n");
+		return -EIO;
+	}
 
-	/* 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);
+	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;
-		}
+		if (sg_is_last(&sg[i]))
+			break;
+	}
 
-		/* but here your code to setup and exectute the dma operation */
-		/* ... */
+	/* put here your code to setup and exectute the dma operation */
+	/* ... */
 
-		/* example: 5 bytes transmitted */
-		ret = 5;
+	/* example: 5 bytes transmitted */
+	ret = 5;
 
-		/* finish the dma operation and update the transmitted data */
-		kfifo_dma_out_finish(&fifo, ret);
-	}
+	/* finish the dma operation and update the transmitted data */
+	kfifo_dma_out_finish(&fifo, ret);
 
+	ret = kfifo_len(&fifo);
 	printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));
 
+	if (ret != 7) {
+		printk(KERN_WARNING "size mismatch: test failed");
+		return -EIO;
+	}
+	printk(KERN_INFO "test passed\n");
+
 	return 0;
 }