[linux-2.6-block.git] / samples / kfifo / dma-example.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Sample fifo dma implementation
 *
 * Copyright (C) 2010 Stefani Seibold <stefani@seibold.net>
 */

#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;
	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_WARNING "error kfifo_alloc\n");
		return -ENOMEM;
	}

	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 */
	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));
	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 %p offset 0x%.8x length 0x%.8x\n",
			i, sg_page(&sg[i]), sg[i].offset, sg[i].length);

		if (sg_is_last(&sg[i]))
			break;
	}

	/* put 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);

	/* 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;
	}

	printk(KERN_INFO "scatterlist for transmit:\n");
	for (i = 0; i < nents; i++) {
		printk(KERN_INFO
		"sg[%d] -> "
		"page %p offset 0x%.8x length 0x%.8x\n",
			i, sg_page(&sg[i]), sg[i].offset, sg[i].length);

		if (sg_is_last(&sg[i]))
			break;
	}

	/* put 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);

	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)
{
	kfifo_free(&fifo);
}

module_init(example_init);
module_exit(example_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");
Commit	Line	Data
912d0f0b	1	// SPDX-License-Identifier: GPL-2.0-only
5bf2b193 SS	2	/*
	3	* Sample fifo dma implementation
	4	*
	5	* Copyright (C) 2010 Stefani Seibold <stefani@seibold.net>
5bf2b193 SS	6	*/
	7
	8	#include <linux/init.h>
	9	#include <linux/module.h>
	10	#include <linux/kfifo.h>
	11
	12	/*
	13	* This module shows how to handle fifo dma operations.
	14	*/
	15
	16	/* fifo size in elements (bytes) */
	17	#define FIFO_SIZE 32
	18
	19	static struct kfifo fifo;
	20
	21	static int __init example_init(void)
	22	{
	23	int i;
	24	unsigned int ret;
399f1e30	25	unsigned int nents;
5bf2b193 SS	26	struct scatterlist sg[10];
	27
	28	printk(KERN_INFO "DMA fifo test start\n");
	29
	30	if (kfifo_alloc(&fifo, FIFO_SIZE, GFP_KERNEL)) {
a25effa4 AR	31	printk(KERN_WARNING "error kfifo_alloc\n");
a25effa4 AR	32	return -ENOMEM;
5bf2b193 SS	33	}
	34
	35	printk(KERN_INFO "queue size: %u\n", kfifo_size(&fifo));
	36
	37	kfifo_in(&fifo, "test", 4);
	38
	39	for (i = 0; i != 9; i++)
498d319b	40	kfifo_put(&fifo, i);
5bf2b193 SS	41
5bf2b193 SS	42	/* kick away first byte */
a25effa4	43	kfifo_skip(&fifo);
5bf2b193 SS	44
	45	printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));
	46
a25effa4 AR	47	/*
	48	* Configure the kfifo buffer to receive data from DMA input.
	49	*
	50	* .--------------------------------------.
	51	* \| 0 \| 1 \| 2 \| ... \| 12 \| 13 \| ... \| 31 \|
	52	* \|---\|------------------\|---------------\|
	53	* \_/ \________________/ \_____________/
	54	* \ \ \
	55	* \ \_allocated data \
	56	* \_free space \_free space
	57	*
	58	* We need two different SG entries: one for the free space area at the
	59	* end of the kfifo buffer (19 bytes) and another for the first free
	60	* byte at the beginning, after the kfifo_skip().
	61	*/
7b34d525	62	sg_init_table(sg, ARRAY_SIZE(sg));
399f1e30 IS	63	nents = kfifo_dma_in_prepare(&fifo, sg, ARRAY_SIZE(sg), FIFO_SIZE);
	64	printk(KERN_INFO "DMA sgl entries: %d\n", nents);
	65	if (!nents) {
a25effa4 AR	66	/* fifo is full and no sgl was created */
	67	printk(KERN_WARNING "error kfifo_dma_in_prepare\n");
	68	return -EIO;
	69	}
5bf2b193	70
a25effa4 AR	71	/* receive data */
a25effa4 AR	72	printk(KERN_INFO "scatterlist for receive:\n");
399f1e30	73	for (i = 0; i < nents; i++) {
a25effa4 AR	74	printk(KERN_INFO
a25effa4 AR	75	"sg[%d] -> "
9263969a LG	76	"page %p offset 0x%.8x length 0x%.8x\n",
9263969a LG	77	i, sg_page(&sg[i]), sg[i].offset, sg[i].length);
5bf2b193	78
a25effa4 AR	79	if (sg_is_last(&sg[i]))
	80	break;
	81	}
5bf2b193	82
a25effa4 AR	83	/* put here your code to setup and exectute the dma operation */
a25effa4 AR	84	/* ... */
5bf2b193	85
a25effa4 AR	86	/* example: zero bytes received */
a25effa4 AR	87	ret = 0;
5bf2b193	88
a25effa4 AR	89	/* finish the dma operation and update the received data */
a25effa4 AR	90	kfifo_dma_in_finish(&fifo, ret);
5bf2b193	91
a25effa4	92	/* Prepare to transmit data, example: 8 bytes */
399f1e30 IS	93	nents = kfifo_dma_out_prepare(&fifo, sg, ARRAY_SIZE(sg), 8);
	94	printk(KERN_INFO "DMA sgl entries: %d\n", nents);
	95	if (!nents) {
a25effa4 AR	96	/* no data was available and no sgl was created */
	97	printk(KERN_WARNING "error kfifo_dma_out_prepare\n");
	98	return -EIO;
	99	}
5bf2b193	100
a25effa4	101	printk(KERN_INFO "scatterlist for transmit:\n");
399f1e30	102	for (i = 0; i < nents; i++) {
a25effa4 AR	103	printk(KERN_INFO
a25effa4 AR	104	"sg[%d] -> "
9263969a LG	105	"page %p offset 0x%.8x length 0x%.8x\n",
9263969a LG	106	i, sg_page(&sg[i]), sg[i].offset, sg[i].length);
5bf2b193	107
a25effa4 AR	108	if (sg_is_last(&sg[i]))
	109	break;
	110	}
5bf2b193	111
a25effa4 AR	112	/* put here your code to setup and exectute the dma operation */
a25effa4 AR	113	/* ... */
5bf2b193	114
a25effa4 AR	115	/* example: 5 bytes transmitted */
a25effa4 AR	116	ret = 5;
5bf2b193	117
a25effa4 AR	118	/* finish the dma operation and update the transmitted data */
a25effa4 AR	119	kfifo_dma_out_finish(&fifo, ret);
5bf2b193	120
a25effa4	121	ret = kfifo_len(&fifo);
5bf2b193 SS	122	printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));
5bf2b193 SS	123
a25effa4 AR	124	if (ret != 7) {
	125	printk(KERN_WARNING "size mismatch: test failed");
	126	return -EIO;
	127	}
	128	printk(KERN_INFO "test passed\n");
	129
5bf2b193 SS	130	return 0;
	131	}
	132
	133	static void __exit example_exit(void)
	134	{
d83a71c4	135	kfifo_free(&fifo);
5bf2b193 SS	136	}
	137
	138	module_init(example_init);
	139	module_exit(example_exit);
	140	MODULE_LICENSE("GPL");
	141	MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");