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/*
* Randomness driver for virtio
* Copyright (C) 2007, 2008 Rusty Russell IBM Corporation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <linux/err.h>
#include <linux/hw_random.h>
#include <linux/scatterlist.h>
#include <linux/spinlock.h>
#include <linux/virtio.h>
#include <linux/virtio_rng.h>
static struct virtqueue *vq;
static unsigned int data_avail;
static DECLARE_COMPLETION(have_data);
static bool busy;
static void random_recv_done(struct virtqueue *vq)
{
/* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
if (!virtqueue_get_buf(vq, &data_avail))
return;
complete(&have_data);
}
/* The host will fill any buffer we give it with sweet, sweet randomness. */
static void register_buffer(u8 *buf, size_t size)
{
struct scatterlist sg;
sg_init_one(&sg, buf, size);
/* There should always be room for one buffer. */
if (virtqueue_add_buf(vq, &sg, 0, 1, buf) < 0)
BUG();
virtqueue_kick(vq);
}
static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
{
if (!busy) {
busy = true;
init_completion(&have_data);
register_buffer(buf, size);
}
if (!wait)
return 0;
wait_for_completion(&have_data);
busy = false;
return data_avail;
}
static void virtio_cleanup(struct hwrng *rng)
{
if (busy)
wait_for_completion(&have_data);
}
static struct hwrng virtio_hwrng = {
.name = "virtio",
.cleanup = virtio_cleanup,
.read = virtio_read,
};
static int virtrng_probe(struct virtio_device *vdev)
{
int err;
if (vq) {
/* We only support one device for now */
return -EBUSY;
}
/* We expect a single virtqueue. */
vq = virtio_find_single_vq(vdev, random_recv_done, "input");
if (IS_ERR(vq)) {
err = PTR_ERR(vq);
vq = NULL;
return err;
}
err = hwrng_register(&virtio_hwrng);
if (err) {
vdev->config->del_vqs(vdev);
vq = NULL;
return err;
}
return 0;
}
static void __devexit virtrng_remove(struct virtio_device *vdev)
{
vdev->config->reset(vdev);
hwrng_unregister(&virtio_hwrng);
vdev->config->del_vqs(vdev);
vq = NULL;
}
static struct virtio_device_id id_table[] = {
{ VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID },
{ 0 },
};
static struct virtio_driver virtio_rng_driver = {
.driver.name = KBUILD_MODNAME,
.driver.owner = THIS_MODULE,
.id_table = id_table,
.probe = virtrng_probe,
.remove = __devexit_p(virtrng_remove),
};
static int __init init(void)
{
return register_virtio_driver(&virtio_rng_driver);
}
static void __exit fini(void)
{
unregister_virtio_driver(&virtio_rng_driver);
}
module_init(init);
module_exit(fini);
MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_DESCRIPTION("Virtio random number driver");
MODULE_LICENSE("GPL");
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