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5bf2b193 SS |
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>"); |