1 // SPDX-License-Identifier: GPL-2.0-only
3  * Sample fifo dma implementation
12 #include <linux/dma-mapping.h>
15  * This module shows how to handle fifo dma operations.
18 /* fifo size in elements (bytes) */
21 static struct kfifo fifo;  variable
30 	printk(KERN_INFO "DMA fifo test start\n");  in example_init()
32 	if (kfifo_alloc(&fifo, FIFO_SIZE, GFP_KERNEL)) {  in example_init()
34 		return -ENOMEM;  in example_init()
37 	printk(KERN_INFO "queue size: %u\n", kfifo_size(&fifo));  in example_init()
39 	kfifo_in(&fifo, "test", 4);  in example_init()
42 		kfifo_put(&fifo, i);  in example_init()
45 	kfifo_skip(&fifo);  in example_init()
47 	printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));  in example_init()
52 	 *  .--------------------------------------.  in example_init()
54 	 *  |---|------------------|---------------|  in example_init()
65 	nents = kfifo_dma_in_prepare(&fifo, sg, ARRAY_SIZE(sg), FIFO_SIZE);  in example_init()
68 		/* fifo is full and no sgl was created */  in example_init()
70 		return -EIO;  in example_init()
77 		"sg[%d] -> "  in example_init()
92 	kfifo_dma_in_finish(&fifo, ret);  in example_init()
95 	nents = kfifo_dma_out_prepare(&fifo, sg, ARRAY_SIZE(sg), 8);  in example_init()
100 		return -EIO;  in example_init()
106 		"sg[%d] -> "  in example_init()
121 	kfifo_dma_out_finish(&fifo, ret);  in example_init()
123 	ret = kfifo_len(&fifo);  in example_init()
124 	printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));  in example_init()
127 		printk(KERN_WARNING "size mismatch: test failed");  in example_init()
128 		return -EIO;  in example_init()
137 	kfifo_free(&fifo);  in example_exit()
142 MODULE_DESCRIPTION("Sample fifo dma implementation");