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/*
* Sample fifo dma implementation
*
* Copyright (C) 2010 Stefani Seibold <stefani@seibold.net>
*
* Released under the GPL version 2 only.
*
*/
#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;
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_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 */
ret = kfifo_get(&fifo, &i);
printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));
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 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;
}
/* but 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);
}
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);
if (sg_is_last(&sg[i]))
break;
}
/* but 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);
}
printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo));
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>");
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