diff options
Diffstat (limited to 'drivers/char/hw_random/virtio-rng.c')
| -rw-r--r-- | drivers/char/hw_random/virtio-rng.c | 155 |
1 files changed, 155 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 000000000000..d0e563e4fc39 --- /dev/null +++ b/drivers/char/hw_random/virtio-rng.c @@ -0,0 +1,155 @@ +/* + * 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> + +/* The host will fill any buffer we give it with sweet, sweet randomness. We + * give it 64 bytes at a time, and the hwrng framework takes it 4 bytes at a + * time. */ +#define RANDOM_DATA_SIZE 64 + +static struct virtqueue *vq; +static u32 *random_data; +static unsigned int data_left; +static DECLARE_COMPLETION(have_data); + +static void random_recv_done(struct virtqueue *vq) +{ + int len; + + /* We never get spurious callbacks. */ + if (!vq->vq_ops->get_buf(vq, &len)) + BUG(); + + data_left = len / sizeof(random_data[0]); + complete(&have_data); +} + +static void register_buffer(void) +{ + struct scatterlist sg; + + sg_init_one(&sg, random_data, RANDOM_DATA_SIZE); + /* There should always be room for one buffer. */ + if (vq->vq_ops->add_buf(vq, &sg, 0, 1, random_data) != 0) + BUG(); + vq->vq_ops->kick(vq); +} + +/* At least we don't udelay() in a loop like some other drivers. */ +static int virtio_data_present(struct hwrng *rng, int wait) +{ + if (data_left) + return 1; + + if (!wait) + return 0; + + wait_for_completion(&have_data); + return 1; +} + +/* virtio_data_present() must have succeeded before this is called. */ +static int virtio_data_read(struct hwrng *rng, u32 *data) +{ + BUG_ON(!data_left); + + *data = random_data[--data_left]; + + if (!data_left) { + init_completion(&have_data); + register_buffer(); + } + return sizeof(*data); +} + +static struct hwrng virtio_hwrng = { + .name = "virtio", + .data_present = virtio_data_present, + .data_read = virtio_data_read, +}; + +static int virtrng_probe(struct virtio_device *vdev) +{ + int err; + + /* We expect a single virtqueue. */ + vq = vdev->config->find_vq(vdev, 0, random_recv_done); + if (IS_ERR(vq)) + return PTR_ERR(vq); + + err = hwrng_register(&virtio_hwrng); + if (err) { + vdev->config->del_vq(vq); + return err; + } + + register_buffer(); + return 0; +} + +static void virtrng_remove(struct virtio_device *vdev) +{ + vdev->config->reset(vdev); + hwrng_unregister(&virtio_hwrng); + vdev->config->del_vq(vq); +} + +static struct virtio_device_id id_table[] = { + { VIRTIO_ID_RNG, VIRTIO_DEV_ANY_ID }, + { 0 }, +}; + +static struct virtio_driver virtio_rng = { + .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) +{ + int err; + + random_data = kmalloc(RANDOM_DATA_SIZE, GFP_KERNEL); + if (!random_data) + return -ENOMEM; + + err = register_virtio_driver(&virtio_rng); + if (err) + kfree(random_data); + return err; +} + +static void __exit fini(void) +{ + kfree(random_data); + unregister_virtio_driver(&virtio_rng); +} +module_init(init); +module_exit(fini); + +MODULE_DEVICE_TABLE(virtio, id_table); +MODULE_DESCRIPTION("Virtio random number driver"); +MODULE_LICENSE("GPL"); |