2 * Randomness driver for virtio
3 * Copyright (C) 2007, 2008 Rusty Russell IBM Corporation
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.
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.
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
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>
28 static DEFINE_IDA(rng_index_ida);
33 struct completion have_data;
35 unsigned int data_avail;
38 bool hwrng_register_done;
42 static void random_recv_done(struct virtqueue *vq)
44 struct virtrng_info *vi = vq->vdev->priv;
46 /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
47 if (!virtqueue_get_buf(vi->vq, &vi->data_avail))
50 complete(&vi->have_data);
53 /* The host will fill any buffer we give it with sweet, sweet randomness. */
54 static void register_buffer(struct virtrng_info *vi, u8 *buf, size_t size)
56 struct scatterlist sg;
58 sg_init_one(&sg, buf, size);
60 /* There should always be room for one buffer. */
61 virtqueue_add_inbuf(vi->vq, &sg, 1, buf, GFP_KERNEL);
63 virtqueue_kick(vi->vq);
66 static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
69 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
71 if (vi->hwrng_removed)
76 init_completion(&vi->have_data);
77 register_buffer(vi, buf, size);
83 ret = wait_for_completion_killable(&vi->have_data);
89 return vi->data_avail;
92 static void virtio_cleanup(struct hwrng *rng)
94 struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
97 wait_for_completion(&vi->have_data);
100 static int probe_common(struct virtio_device *vdev)
103 struct virtrng_info *vi = NULL;
105 vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
109 vi->index = index = ida_simple_get(&rng_index_ida, 0, 0, GFP_KERNEL);
114 sprintf(vi->name, "virtio_rng.%d", index);
115 init_completion(&vi->have_data);
117 vi->hwrng = (struct hwrng) {
119 .cleanup = virtio_cleanup,
120 .priv = (unsigned long)vi,
126 /* We expect a single virtqueue. */
127 vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
128 if (IS_ERR(vi->vq)) {
129 err = PTR_ERR(vi->vq);
136 ida_simple_remove(&rng_index_ida, index);
142 static void remove_common(struct virtio_device *vdev)
144 struct virtrng_info *vi = vdev->priv;
146 vi->hwrng_removed = true;
148 complete(&vi->have_data);
149 vdev->config->reset(vdev);
151 if (vi->hwrng_register_done)
152 hwrng_unregister(&vi->hwrng);
153 vdev->config->del_vqs(vdev);
154 ida_simple_remove(&rng_index_ida, vi->index);
158 static int virtrng_probe(struct virtio_device *vdev)
160 return probe_common(vdev);
163 static void virtrng_remove(struct virtio_device *vdev)
168 static void virtrng_scan(struct virtio_device *vdev)
170 struct virtrng_info *vi = vdev->priv;
173 err = hwrng_register(&vi->hwrng);
175 vi->hwrng_register_done = true;
178 #ifdef CONFIG_PM_SLEEP
179 static int virtrng_freeze(struct virtio_device *vdev)
185 static int virtrng_restore(struct virtio_device *vdev)
187 return probe_common(vdev);
191 static struct virtio_device_id id_table[] = {
192 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
196 static struct virtio_driver virtio_rng_driver = {
197 .driver.name = KBUILD_MODNAME,
198 .driver.owner = THIS_MODULE,
199 .id_table = id_table,
200 .probe = virtrng_probe,
201 .remove = virtrng_remove,
202 .scan = virtrng_scan,
203 #ifdef CONFIG_PM_SLEEP
204 .freeze = virtrng_freeze,
205 .restore = virtrng_restore,
209 module_virtio_driver(virtio_rng_driver);
210 MODULE_DEVICE_TABLE(virtio, id_table);
211 MODULE_DESCRIPTION("Virtio random number driver");
212 MODULE_LICENSE("GPL");