1 /* 2 * Sample fifo dma implementation 3 * 4 * Copyright (C) 2010 Stefani Seibold <stefani@seibold.net> 5 * 6 * Released under the GPL version 2 only. 7 * 8 */ 9 10 #include <linux/init.h> 11 #include <linux/module.h> 12 #include <linux/kfifo.h> 13 14 /* 15 * This module shows how to handle fifo dma operations. 16 */ 17 18 /* fifo size in elements (bytes) */ 19 #define FIFO_SIZE 32 20 21 static struct kfifo fifo; 22 23 static int __init example_init(void) 24 { 25 int i; 26 unsigned int ret; 27 struct scatterlist sg[10]; 28 29 printk(KERN_INFO "DMA fifo test start\n"); 30 31 if (kfifo_alloc(&fifo, FIFO_SIZE, GFP_KERNEL)) { 32 printk(KERN_ERR "error kfifo_alloc\n"); 33 return 1; 34 } 35 36 printk(KERN_INFO "queue size: %u\n", kfifo_size(&fifo)); 37 38 kfifo_in(&fifo, "test", 4); 39 40 for (i = 0; i != 9; i++) 41 kfifo_put(&fifo, &i); 42 43 /* kick away first byte */ 44 ret = kfifo_get(&fifo, &i); 45 46 printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo)); 47 48 ret = kfifo_dma_in_prepare(&fifo, sg, ARRAY_SIZE(sg), FIFO_SIZE); 49 printk(KERN_INFO "DMA sgl entries: %d\n", ret); 50 51 /* if 0 was returned, fifo is full and no sgl was created */ 52 if (ret) { 53 printk(KERN_INFO "scatterlist for receive:\n"); 54 for (i = 0; i < ARRAY_SIZE(sg); i++) { 55 printk(KERN_INFO 56 "sg[%d] -> " 57 "page_link 0x%.8lx offset 0x%.8x length 0x%.8x\n", 58 i, sg[i].page_link, sg[i].offset, sg[i].length); 59 60 if (sg_is_last(&sg[i])) 61 break; 62 } 63 64 /* but here your code to setup and exectute the dma operation */ 65 /* ... */ 66 67 /* example: zero bytes received */ 68 ret = 0; 69 70 /* finish the dma operation and update the received data */ 71 kfifo_dma_in_finish(&fifo, ret); 72 } 73 74 ret = kfifo_dma_out_prepare(&fifo, sg, ARRAY_SIZE(sg), 8); 75 printk(KERN_INFO "DMA sgl entries: %d\n", ret); 76 77 /* if 0 was returned, no data was available and no sgl was created */ 78 if (ret) { 79 printk(KERN_INFO "scatterlist for transmit:\n"); 80 for (i = 0; i < ARRAY_SIZE(sg); i++) { 81 printk(KERN_INFO 82 "sg[%d] -> " 83 "page_link 0x%.8lx offset 0x%.8x length 0x%.8x\n", 84 i, sg[i].page_link, sg[i].offset, sg[i].length); 85 86 if (sg_is_last(&sg[i])) 87 break; 88 } 89 90 /* but here your code to setup and exectute the dma operation */ 91 /* ... */ 92 93 /* example: 5 bytes transmitted */ 94 ret = 5; 95 96 /* finish the dma operation and update the transmitted data */ 97 kfifo_dma_out_finish(&fifo, ret); 98 } 99 100 printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo)); 101 102 return 0; 103 } 104 105 static void __exit example_exit(void) 106 { 107 #ifdef DYNAMIC 108 kfifo_free(&test); 109 #endif 110 } 111 112 module_init(example_init); 113 module_exit(example_exit); 114 MODULE_LICENSE("GPL"); 115 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); 116