Something went wrong. Try again.
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Something went wrong. Try again.
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145// 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/kfifo.h>#include <linux/module.h>#include <linux/scatterlist.h>#include <linux/dma-mapping.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_DESCRIPTION("Sample fifo dma implementation");MODULE_LICENSE("GPL");MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");