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f7f510ec RR |
1 | /* |
2 | * Randomness driver for virtio | |
3 | * Copyright (C) 2007, 2008 Rusty Russell IBM Corporation | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify | |
6 | * it under the terms of the GNU General Public License as published by | |
7 | * the Free Software Foundation; either version 2 of the License, or | |
8 | * (at your option) any later version. | |
9 | * | |
10 | * This program is distributed in the hope that it will be useful, | |
11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 | * GNU General Public License for more details. | |
14 | * | |
15 | * You should have received a copy of the GNU General Public License | |
16 | * along with this program; if not, write to the Free Software | |
17 | * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA | |
18 | */ | |
bb347d98 | 19 | |
f7f510ec RR |
20 | #include <linux/err.h> |
21 | #include <linux/hw_random.h> | |
22 | #include <linux/scatterlist.h> | |
23 | #include <linux/spinlock.h> | |
24 | #include <linux/virtio.h> | |
25 | #include <linux/virtio_rng.h> | |
c22405c9 | 26 | #include <linux/module.h> |
f7f510ec | 27 | |
f7f510ec | 28 | static struct virtqueue *vq; |
bb347d98 | 29 | static unsigned int data_avail; |
f7f510ec | 30 | static DECLARE_COMPLETION(have_data); |
bb347d98 | 31 | static bool busy; |
f7f510ec RR |
32 | |
33 | static void random_recv_done(struct virtqueue *vq) | |
34 | { | |
e5b89542 | 35 | /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */ |
28cfc828 | 36 | if (!virtqueue_get_buf(vq, &data_avail)) |
e5b89542 | 37 | return; |
f7f510ec | 38 | |
f7f510ec RR |
39 | complete(&have_data); |
40 | } | |
41 | ||
bb347d98 IM |
42 | /* The host will fill any buffer we give it with sweet, sweet randomness. */ |
43 | static void register_buffer(u8 *buf, size_t size) | |
f7f510ec RR |
44 | { |
45 | struct scatterlist sg; | |
46 | ||
bb347d98 IM |
47 | sg_init_one(&sg, buf, size); |
48 | ||
f7f510ec | 49 | /* There should always be room for one buffer. */ |
28cfc828 | 50 | if (virtqueue_add_buf(vq, &sg, 0, 1, buf) < 0) |
f7f510ec | 51 | BUG(); |
bb347d98 | 52 | |
28cfc828 | 53 | virtqueue_kick(vq); |
f7f510ec RR |
54 | } |
55 | ||
bb347d98 | 56 | static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) |
f7f510ec | 57 | { |
f7f510ec | 58 | |
bb347d98 IM |
59 | if (!busy) { |
60 | busy = true; | |
61 | init_completion(&have_data); | |
62 | register_buffer(buf, size); | |
63 | } | |
64 | ||
f7f510ec RR |
65 | if (!wait) |
66 | return 0; | |
67 | ||
68 | wait_for_completion(&have_data); | |
594de1dd | 69 | |
bb347d98 | 70 | busy = false; |
594de1dd | 71 | |
bb347d98 | 72 | return data_avail; |
f7f510ec RR |
73 | } |
74 | ||
bb347d98 | 75 | static void virtio_cleanup(struct hwrng *rng) |
f7f510ec | 76 | { |
bb347d98 IM |
77 | if (busy) |
78 | wait_for_completion(&have_data); | |
f7f510ec RR |
79 | } |
80 | ||
bb347d98 | 81 | |
f7f510ec | 82 | static struct hwrng virtio_hwrng = { |
bb347d98 IM |
83 | .name = "virtio", |
84 | .cleanup = virtio_cleanup, | |
85 | .read = virtio_read, | |
f7f510ec RR |
86 | }; |
87 | ||
88 | static int virtrng_probe(struct virtio_device *vdev) | |
89 | { | |
90 | int err; | |
91 | ||
92 | /* We expect a single virtqueue. */ | |
d2a7ddda | 93 | vq = virtio_find_single_vq(vdev, random_recv_done, "input"); |
f7f510ec RR |
94 | if (IS_ERR(vq)) |
95 | return PTR_ERR(vq); | |
96 | ||
97 | err = hwrng_register(&virtio_hwrng); | |
98 | if (err) { | |
d2a7ddda | 99 | vdev->config->del_vqs(vdev); |
f7f510ec RR |
100 | return err; |
101 | } | |
102 | ||
f7f510ec RR |
103 | return 0; |
104 | } | |
105 | ||
ff07eb89 | 106 | static void __devexit virtrng_remove(struct virtio_device *vdev) |
f7f510ec RR |
107 | { |
108 | vdev->config->reset(vdev); | |
109 | hwrng_unregister(&virtio_hwrng); | |
d2a7ddda | 110 | vdev->config->del_vqs(vdev); |
f7f510ec RR |
111 | } |
112 | ||
113 | static struct virtio_device_id id_table[] = { | |
114 | { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID }, | |
115 | { 0 }, | |
116 | }; | |
117 | ||
d817cd52 | 118 | static struct virtio_driver virtio_rng_driver = { |
f7f510ec RR |
119 | .driver.name = KBUILD_MODNAME, |
120 | .driver.owner = THIS_MODULE, | |
121 | .id_table = id_table, | |
122 | .probe = virtrng_probe, | |
123 | .remove = __devexit_p(virtrng_remove), | |
124 | }; | |
125 | ||
126 | static int __init init(void) | |
127 | { | |
d817cd52 | 128 | return register_virtio_driver(&virtio_rng_driver); |
f7f510ec RR |
129 | } |
130 | ||
131 | static void __exit fini(void) | |
132 | { | |
d817cd52 | 133 | unregister_virtio_driver(&virtio_rng_driver); |
f7f510ec RR |
134 | } |
135 | module_init(init); | |
136 | module_exit(fini); | |
137 | ||
138 | MODULE_DEVICE_TABLE(virtio, id_table); | |
139 | MODULE_DESCRIPTION("Virtio random number driver"); | |
140 | MODULE_LICENSE("GPL"); |