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 struct virtqueue *vq;
29 static unsigned int data_avail;
30 static DECLARE_COMPLETION(have_data);
33 static void random_recv_done(struct virtqueue *vq)
35 /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
36 if (!virtqueue_get_buf(vq, &data_avail))
42 /* The host will fill any buffer we give it with sweet, sweet randomness. */
43 static void register_buffer(u8 *buf, size_t size)
45 struct scatterlist sg;
47 sg_init_one(&sg, buf, size);
49 /* There should always be room for one buffer. */
50 virtqueue_add_inbuf(vq, &sg, 1, buf, GFP_KERNEL);
55 static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
61 init_completion(&have_data);
62 register_buffer(buf, size);
68 ret = wait_for_completion_killable(&have_data);
77 static void virtio_cleanup(struct hwrng *rng)
80 wait_for_completion(&have_data);
84 static struct hwrng virtio_hwrng = {
86 .cleanup = virtio_cleanup,
90 static int probe_common(struct virtio_device *vdev)
95 /* We only support one device for now */
98 /* We expect a single virtqueue. */
99 vq = virtio_find_single_vq(vdev, random_recv_done, "input");
106 err = hwrng_register(&virtio_hwrng);
108 vdev->config->del_vqs(vdev);
116 static void remove_common(struct virtio_device *vdev)
118 vdev->config->reset(vdev);
120 hwrng_unregister(&virtio_hwrng);
121 vdev->config->del_vqs(vdev);
125 static int virtrng_probe(struct virtio_device *vdev)
127 return probe_common(vdev);
130 static void virtrng_remove(struct virtio_device *vdev)
135 #ifdef CONFIG_PM_SLEEP
136 static int virtrng_freeze(struct virtio_device *vdev)
142 static int virtrng_restore(struct virtio_device *vdev)
144 return probe_common(vdev);
148 static struct virtio_device_id id_table[] = {
149 { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
153 static struct virtio_driver virtio_rng_driver = {
154 .driver.name = KBUILD_MODNAME,
155 .driver.owner = THIS_MODULE,
156 .id_table = id_table,
157 .probe = virtrng_probe,
158 .remove = virtrng_remove,
159 #ifdef CONFIG_PM_SLEEP
160 .freeze = virtrng_freeze,
161 .restore = virtrng_restore,
165 module_virtio_driver(virtio_rng_driver);
166 MODULE_DEVICE_TABLE(virtio, id_table);
167 MODULE_DESCRIPTION("Virtio random number driver");
168 MODULE_LICENSE("GPL");