1 // SPDX-License-Identifier: GPL-2.0-only
3  * Sample fifo dma implementation
13  * This module shows how to handle fifo dma operations.
16 /* fifo size in elements (bytes) */
19 static struct kfifo fifo;  variable
28 	printk(KERN_INFO "DMA fifo test start\n");  in example_init()
30 	if (kfifo_alloc(&fifo, FIFO_SIZE, GFP_KERNEL)) {  in example_init()
32 		return -ENOMEM;  in example_init()
35 	printk(KERN_INFO "queue size: %u\n", kfifo_size(&fifo));  in example_init()
37 	kfifo_in(&fifo, "test", 4);  in example_init()
40 		kfifo_put(&fifo, i);  in example_init()
43 	kfifo_skip(&fifo);  in example_init()
45 	printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));  in example_init()
50 	 *  .--------------------------------------.  in example_init()
52 	 *  |---|------------------|---------------|  in example_init()
63 	nents = kfifo_dma_in_prepare(&fifo, sg, ARRAY_SIZE(sg), FIFO_SIZE);  in example_init()
66 		/* fifo is full and no sgl was created */  in example_init()
68 		return -EIO;  in example_init()
75 		"sg[%d] -> "  in example_init()
90 	kfifo_dma_in_finish(&fifo, ret);  in example_init()
93 	nents = kfifo_dma_out_prepare(&fifo, sg, ARRAY_SIZE(sg), 8);  in example_init()
98 		return -EIO;  in example_init()
104 		"sg[%d] -> "  in example_init()
119 	kfifo_dma_out_finish(&fifo, ret);  in example_init()
121 	ret = kfifo_len(&fifo);  in example_init()
122 	printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));  in example_init()
125 		printk(KERN_WARNING "size mismatch: test failed");  in example_init()
126 		return -EIO;  in example_init()
135 	kfifo_free(&fifo);  in example_exit()