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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> | |
26 | ||
f7f510ec | 27 | static struct virtqueue *vq; |
bb347d98 | 28 | static unsigned int data_avail; |
f7f510ec | 29 | static DECLARE_COMPLETION(have_data); |
bb347d98 | 30 | static bool busy; |
f7f510ec RR |
31 | |
32 | static void random_recv_done(struct virtqueue *vq) | |
33 | { | |
e5b89542 | 34 | /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */ |
bb347d98 | 35 | if (!vq->vq_ops->get_buf(vq, &data_avail)) |
e5b89542 | 36 | return; |
f7f510ec | 37 | |
f7f510ec RR |
38 | complete(&have_data); |
39 | } | |
40 | ||
bb347d98 IM |
41 | /* The host will fill any buffer we give it with sweet, sweet randomness. */ |
42 | static void register_buffer(u8 *buf, size_t size) | |
f7f510ec RR |
43 | { |
44 | struct scatterlist sg; | |
45 | ||
bb347d98 IM |
46 | sg_init_one(&sg, buf, size); |
47 | ||
f7f510ec | 48 | /* There should always be room for one buffer. */ |
bb347d98 | 49 | if (vq->vq_ops->add_buf(vq, &sg, 0, 1, buf) < 0) |
f7f510ec | 50 | BUG(); |
bb347d98 | 51 | |
f7f510ec RR |
52 | vq->vq_ops->kick(vq); |
53 | } | |
54 | ||
bb347d98 | 55 | static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) |
f7f510ec | 56 | { |
f7f510ec | 57 | |
bb347d98 IM |
58 | if (!busy) { |
59 | busy = true; | |
60 | init_completion(&have_data); | |
61 | register_buffer(buf, size); | |
62 | } | |
63 | ||
f7f510ec RR |
64 | if (!wait) |
65 | return 0; | |
66 | ||
67 | wait_for_completion(&have_data); | |
594de1dd | 68 | |
bb347d98 | 69 | busy = false; |
594de1dd | 70 | |
bb347d98 | 71 | return data_avail; |
f7f510ec RR |
72 | } |
73 | ||
bb347d98 | 74 | static void virtio_cleanup(struct hwrng *rng) |
f7f510ec | 75 | { |
bb347d98 IM |
76 | if (busy) |
77 | wait_for_completion(&have_data); | |
f7f510ec RR |
78 | } |
79 | ||
bb347d98 | 80 | |
f7f510ec | 81 | static struct hwrng virtio_hwrng = { |
bb347d98 IM |
82 | .name = "virtio", |
83 | .cleanup = virtio_cleanup, | |
84 | .read = virtio_read, | |
f7f510ec RR |
85 | }; |
86 | ||
87 | static int virtrng_probe(struct virtio_device *vdev) | |
88 | { | |
89 | int err; | |
90 | ||
91 | /* We expect a single virtqueue. */ | |
d2a7ddda | 92 | vq = virtio_find_single_vq(vdev, random_recv_done, "input"); |
f7f510ec RR |
93 | if (IS_ERR(vq)) |
94 | return PTR_ERR(vq); | |
95 | ||
96 | err = hwrng_register(&virtio_hwrng); | |
97 | if (err) { | |
d2a7ddda | 98 | vdev->config->del_vqs(vdev); |
f7f510ec RR |
99 | return err; |
100 | } | |
101 | ||
f7f510ec RR |
102 | return 0; |
103 | } | |
104 | ||
ff07eb89 | 105 | static void __devexit virtrng_remove(struct virtio_device *vdev) |
f7f510ec RR |
106 | { |
107 | vdev->config->reset(vdev); | |
108 | hwrng_unregister(&virtio_hwrng); | |
d2a7ddda | 109 | vdev->config->del_vqs(vdev); |
f7f510ec RR |
110 | } |
111 | ||
112 | static struct virtio_device_id id_table[] = { | |
113 | { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID }, | |
114 | { 0 }, | |
115 | }; | |
116 | ||
117 | static struct virtio_driver virtio_rng = { | |
118 | .driver.name = KBUILD_MODNAME, | |
119 | .driver.owner = THIS_MODULE, | |
120 | .id_table = id_table, | |
121 | .probe = virtrng_probe, | |
122 | .remove = __devexit_p(virtrng_remove), | |
123 | }; | |
124 | ||
125 | static int __init init(void) | |
126 | { | |
bb347d98 | 127 | return register_virtio_driver(&virtio_rng); |
f7f510ec RR |
128 | } |
129 | ||
130 | static void __exit fini(void) | |
131 | { | |
f7f510ec RR |
132 | unregister_virtio_driver(&virtio_rng); |
133 | } | |
134 | module_init(init); | |
135 | module_exit(fini); | |
136 | ||
137 | MODULE_DEVICE_TABLE(virtio, id_table); | |
138 | MODULE_DESCRIPTION("Virtio random number driver"); | |
139 | MODULE_LICENSE("GPL"); |