1 files changed, 140 insertions, 0 deletions
diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
new file mode 100644
index 00000000..723725bb
--- /dev/null
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -0,0 +1,140 @@
+/*
+ * 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>
+#include <linux/module.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, GFP_KERNEL) < 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;
+
+	/* We expect a single virtqueue. */
+	vq = virtio_find_single_vq(vdev, random_recv_done, "input");
+	if (IS_ERR(vq))
+		return PTR_ERR(vq);
+
+	err = hwrng_register(&virtio_hwrng);
+	if (err) {
+		vdev->config->del_vqs(vdev);
+		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);
+}
+
+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");