Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wirel...
[linux-2.6.git] / samples / kfifo / dma-example.c
index b9482c2..0647379 100644 (file)
@@ -24,13 +24,14 @@ static int __init example_init(void)
 {
        int                     i;
        unsigned int            ret;
+       unsigned int            nents;
        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_WARNING "error kfifo_alloc\n");
+               return -ENOMEM;
        }
 
        printk(KERN_INFO "queue size: %u\n", kfifo_size(&fifo));
@@ -41,72 +42,99 @@ 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));
 
-       ret = kfifo_dma_in_prepare(&fifo, sg, ARRAY_SIZE(sg), FIFO_SIZE);
-       printk(KERN_INFO "DMA sgl entries: %d\n", ret);
+       /*
+        * 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));
+       nents = kfifo_dma_in_prepare(&fifo, sg, ARRAY_SIZE(sg), FIFO_SIZE);
+       printk(KERN_INFO "DMA sgl entries: %d\n", nents);
+       if (!nents) {
+               /* fifo is full and no sgl was created */
+               printk(KERN_WARNING "error kfifo_dma_in_prepare\n");
+               return -EIO;
+       }
+
+       /* receive data */
+       printk(KERN_INFO "scatterlist for receive:\n");
+       for (i = 0; i < nents; 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 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;
+       }
 
-                       if (sg_is_last(&sg[i]))
-                               break;
-               }
+       /* put here your code to setup and exectute the dma operation */
+       /* ... */
 
-               /* but 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 */
+       nents = kfifo_dma_out_prepare(&fifo, sg, ARRAY_SIZE(sg), 8);
+       printk(KERN_INFO "DMA sgl entries: %d\n", nents);
+       if (!nents) {
+               /* no data was available and no sgl was created */
+               printk(KERN_WARNING "error kfifo_dma_out_prepare\n");
+               return -EIO;
        }
 
-       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);
+       printk(KERN_INFO "scatterlist for transmit:\n");
+       for (i = 0; i < nents; 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;
 }
 
 static void __exit example_exit(void)
 {
-#ifdef DYNAMIC
-       kfifo_free(&test);
-#endif
+       kfifo_free(&fifo);
 }
 
 module_init(example_init);