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