| | 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_inbuf(vq, &sg, 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"); |
projects / GitHub / mt8127 / android_kernel_alcatel_ttab.git / blame_incremental