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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. */ |
f96fde41 | 50 | if (virtqueue_add_buf(vq, &sg, 0, 1, buf, GFP_KERNEL) < 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 | { |
cc8744e1 | 58 | int ret; |
f7f510ec | 59 | |
bb347d98 IM |
60 | if (!busy) { |
61 | busy = true; | |
62 | init_completion(&have_data); | |
63 | register_buffer(buf, size); | |
64 | } | |
65 | ||
f7f510ec RR |
66 | if (!wait) |
67 | return 0; | |
68 | ||
cc8744e1 AS |
69 | ret = wait_for_completion_killable(&have_data); |
70 | if (ret < 0) | |
71 | return ret; | |
594de1dd | 72 | |
bb347d98 | 73 | busy = false; |
594de1dd | 74 | |
bb347d98 | 75 | return data_avail; |
f7f510ec RR |
76 | } |
77 | ||
bb347d98 | 78 | static void virtio_cleanup(struct hwrng *rng) |
f7f510ec | 79 | { |
bb347d98 IM |
80 | if (busy) |
81 | wait_for_completion(&have_data); | |
f7f510ec RR |
82 | } |
83 | ||
bb347d98 | 84 | |
f7f510ec | 85 | static struct hwrng virtio_hwrng = { |
bb347d98 IM |
86 | .name = "virtio", |
87 | .cleanup = virtio_cleanup, | |
88 | .read = virtio_read, | |
f7f510ec RR |
89 | }; |
90 | ||
178d855e | 91 | static int probe_common(struct virtio_device *vdev) |
f7f510ec RR |
92 | { |
93 | int err; | |
94 | ||
95 | /* We expect a single virtqueue. */ | |
d2a7ddda | 96 | vq = virtio_find_single_vq(vdev, random_recv_done, "input"); |
f7f510ec RR |
97 | if (IS_ERR(vq)) |
98 | return PTR_ERR(vq); | |
99 | ||
100 | err = hwrng_register(&virtio_hwrng); | |
101 | if (err) { | |
d2a7ddda | 102 | vdev->config->del_vqs(vdev); |
f7f510ec RR |
103 | return err; |
104 | } | |
105 | ||
f7f510ec RR |
106 | return 0; |
107 | } | |
108 | ||
178d855e | 109 | static void remove_common(struct virtio_device *vdev) |
f7f510ec RR |
110 | { |
111 | vdev->config->reset(vdev); | |
4476987a | 112 | busy = false; |
f7f510ec | 113 | hwrng_unregister(&virtio_hwrng); |
d2a7ddda | 114 | vdev->config->del_vqs(vdev); |
f7f510ec RR |
115 | } |
116 | ||
178d855e AS |
117 | static int virtrng_probe(struct virtio_device *vdev) |
118 | { | |
119 | return probe_common(vdev); | |
120 | } | |
121 | ||
122 | static void __devexit virtrng_remove(struct virtio_device *vdev) | |
123 | { | |
124 | remove_common(vdev); | |
125 | } | |
126 | ||
0bc1a2ef AS |
127 | #ifdef CONFIG_PM |
128 | static int virtrng_freeze(struct virtio_device *vdev) | |
129 | { | |
130 | remove_common(vdev); | |
131 | return 0; | |
132 | } | |
133 | ||
134 | static int virtrng_restore(struct virtio_device *vdev) | |
135 | { | |
136 | return probe_common(vdev); | |
137 | } | |
138 | #endif | |
139 | ||
f7f510ec RR |
140 | static struct virtio_device_id id_table[] = { |
141 | { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID }, | |
142 | { 0 }, | |
143 | }; | |
144 | ||
d817cd52 | 145 | static struct virtio_driver virtio_rng_driver = { |
f7f510ec RR |
146 | .driver.name = KBUILD_MODNAME, |
147 | .driver.owner = THIS_MODULE, | |
148 | .id_table = id_table, | |
149 | .probe = virtrng_probe, | |
150 | .remove = __devexit_p(virtrng_remove), | |
0bc1a2ef AS |
151 | #ifdef CONFIG_PM |
152 | .freeze = virtrng_freeze, | |
153 | .restore = virtrng_restore, | |
154 | #endif | |
f7f510ec RR |
155 | }; |
156 | ||
157 | static int __init init(void) | |
158 | { | |
d817cd52 | 159 | return register_virtio_driver(&virtio_rng_driver); |
f7f510ec RR |
160 | } |
161 | ||
162 | static void __exit fini(void) | |
163 | { | |
d817cd52 | 164 | unregister_virtio_driver(&virtio_rng_driver); |
f7f510ec RR |
165 | } |
166 | module_init(init); | |
167 | module_exit(fini); | |
168 | ||
169 | MODULE_DEVICE_TABLE(virtio, id_table); | |
170 | MODULE_DESCRIPTION("Virtio random number driver"); | |
171 | MODULE_LICENSE("GPL"); |