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| 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 | */ |
| 19 | |
| 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 | #include <linux/module.h> |
| 27 | |
| 28 | static struct virtqueue *vq; |
| 29 | static unsigned int data_avail; |
| 30 | static DECLARE_COMPLETION(have_data); |
| 31 | static bool busy; |
| 32 | |
| 33 | static void random_recv_done(struct virtqueue *vq) |
| 34 | { |
| 35 | /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */ |
| 36 | if (!virtqueue_get_buf(vq, &data_avail)) |
| 37 | return; |
| 38 | |
| 39 | complete(&have_data); |
| 40 | } |
| 41 | |
| 42 | /* The host will fill any buffer we give it with sweet, sweet randomness. */ |
| 43 | static void register_buffer(u8 *buf, size_t size) |
| 44 | { |
| 45 | struct scatterlist sg; |
| 46 | |
| 47 | sg_init_one(&sg, buf, size); |
| 48 | |
| 49 | /* There should always be room for one buffer. */ |
| 50 | if (virtqueue_add_buf(vq, &sg, 0, 1, buf, GFP_KERNEL) < 0) |
| 51 | BUG(); |
| 52 | |
| 53 | virtqueue_kick(vq); |
| 54 | } |
| 55 | |
| 56 | static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) |
| 57 | { |
| 58 | int ret; |
| 59 | |
| 60 | if (!busy) { |
| 61 | busy = true; |
| 62 | init_completion(&have_data); |
| 63 | register_buffer(buf, size); |
| 64 | } |
| 65 | |
| 66 | if (!wait) |
| 67 | return 0; |
| 68 | |
| 69 | ret = wait_for_completion_killable(&have_data); |
| 70 | if (ret < 0) |
| 71 | return ret; |
| 72 | |
| 73 | busy = false; |
| 74 | |
| 75 | return data_avail; |
| 76 | } |
| 77 | |
| 78 | static void virtio_cleanup(struct hwrng *rng) |
| 79 | { |
| 80 | if (busy) |
| 81 | wait_for_completion(&have_data); |
| 82 | } |
| 83 | |
| 84 | |
| 85 | static struct hwrng virtio_hwrng = { |
| 86 | .name = "virtio", |
| 87 | .cleanup = virtio_cleanup, |
| 88 | .read = virtio_read, |
| 89 | }; |
| 90 | |
| 91 | static int probe_common(struct virtio_device *vdev) |
| 92 | { |
| 93 | int err; |
| 94 | |
| 95 | if (vq) { |
| 96 | /* We only support one device for now */ |
| 97 | return -EBUSY; |
| 98 | } |
| 99 | /* We expect a single virtqueue. */ |
| 100 | vq = virtio_find_single_vq(vdev, random_recv_done, "input"); |
| 101 | if (IS_ERR(vq)) { |
| 102 | err = PTR_ERR(vq); |
| 103 | vq = NULL; |
| 104 | return err; |
| 105 | } |
| 106 | |
| 107 | err = hwrng_register(&virtio_hwrng); |
| 108 | if (err) { |
| 109 | vdev->config->del_vqs(vdev); |
| 110 | vq = NULL; |
| 111 | return err; |
| 112 | } |
| 113 | |
| 114 | return 0; |
| 115 | } |
| 116 | |
| 117 | static void remove_common(struct virtio_device *vdev) |
| 118 | { |
| 119 | vdev->config->reset(vdev); |
| 120 | busy = false; |
| 121 | hwrng_unregister(&virtio_hwrng); |
| 122 | vdev->config->del_vqs(vdev); |
| 123 | vq = NULL; |
| 124 | } |
| 125 | |
| 126 | static int virtrng_probe(struct virtio_device *vdev) |
| 127 | { |
| 128 | return probe_common(vdev); |
| 129 | } |
| 130 | |
| 131 | static void virtrng_remove(struct virtio_device *vdev) |
| 132 | { |
| 133 | remove_common(vdev); |
| 134 | } |
| 135 | |
| 136 | #ifdef CONFIG_PM |
| 137 | static int virtrng_freeze(struct virtio_device *vdev) |
| 138 | { |
| 139 | remove_common(vdev); |
| 140 | return 0; |
| 141 | } |
| 142 | |
| 143 | static int virtrng_restore(struct virtio_device *vdev) |
| 144 | { |
| 145 | return probe_common(vdev); |
| 146 | } |
| 147 | #endif |
| 148 | |
| 149 | static struct virtio_device_id id_table[] = { |
| 150 | { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID }, |
| 151 | { 0 }, |
| 152 | }; |
| 153 | |
| 154 | static struct virtio_driver virtio_rng_driver = { |
| 155 | .driver.name = KBUILD_MODNAME, |
| 156 | .driver.owner = THIS_MODULE, |
| 157 | .id_table = id_table, |
| 158 | .probe = virtrng_probe, |
| 159 | .remove = virtrng_remove, |
| 160 | #ifdef CONFIG_PM |
| 161 | .freeze = virtrng_freeze, |
| 162 | .restore = virtrng_restore, |
| 163 | #endif |
| 164 | }; |
| 165 | |
| 166 | module_virtio_driver(virtio_rng_driver); |
| 167 | MODULE_DEVICE_TABLE(virtio, id_table); |
| 168 | MODULE_DESCRIPTION("Virtio random number driver"); |
| 169 | MODULE_LICENSE("GPL"); |
| 170 |
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
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v3.9
