2 * chaoskey - driver for ChaosKey device from Altus Metrum.
4 * This device provides true random numbers using a noise source based
5 * on a reverse-biased p-n junction in avalanche breakdown. More
6 * details can be found at http://chaoskey.org
8 * The driver connects to the kernel hardware RNG interface to provide
9 * entropy for /dev/random and other kernel activities. It also offers
10 * a separate /dev/ entry to allow for direct access to the random
13 * Copyright © 2015 Keith Packard <keithp@keithp.com>
15 * This program is free software; you can redistribute it and/or modify
16 * it under the terms of the GNU General Public License as published by
17 * the Free Software Foundation; version 2 of the License.
19 * This program is distributed in the hope that it will be useful, but
20 * WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
22 * General Public License for more details.
25 #include <linux/module.h>
26 #include <linux/slab.h>
27 #include <linux/usb.h>
28 #include <linux/wait.h>
29 #include <linux/hw_random.h>
30 #include <linux/mutex.h>
31 #include <linux/uaccess.h>
33 static struct usb_driver chaoskey_driver;
34 static struct usb_class_driver chaoskey_class;
35 static int chaoskey_rng_read(struct hwrng *rng, void *data,
36 size_t max, bool wait);
38 #define usb_dbg(usb_if, format, arg...) \
39 dev_dbg(&(usb_if)->dev, format, ## arg)
41 #define usb_err(usb_if, format, arg...) \
42 dev_err(&(usb_if)->dev, format, ## arg)
44 /* Version Information */
45 #define DRIVER_VERSION "v0.1"
46 #define DRIVER_AUTHOR "Keith Packard, keithp@keithp.com"
47 #define DRIVER_DESC "Altus Metrum ChaosKey driver"
48 #define DRIVER_SHORT "chaoskey"
50 MODULE_VERSION(DRIVER_VERSION);
51 MODULE_AUTHOR(DRIVER_AUTHOR);
52 MODULE_DESCRIPTION(DRIVER_DESC);
53 MODULE_LICENSE("GPL");
55 #define CHAOSKEY_VENDOR_ID 0x1d50 /* OpenMoko */
56 #define CHAOSKEY_PRODUCT_ID 0x60c6 /* ChaosKey */
58 #define CHAOSKEY_BUF_LEN 64 /* max size of USB full speed packet */
60 #define NAK_TIMEOUT (HZ) /* stall/wait timeout for device */
62 #ifdef CONFIG_USB_DYNAMIC_MINORS
63 #define USB_CHAOSKEY_MINOR_BASE 0
66 /* IOWARRIOR_MINOR_BASE + 16, not official yet */
67 #define USB_CHAOSKEY_MINOR_BASE 224
70 static const struct usb_device_id chaoskey_table[] = {
71 { USB_DEVICE(CHAOSKEY_VENDOR_ID, CHAOSKEY_PRODUCT_ID) },
74 MODULE_DEVICE_TABLE(usb, chaoskey_table);
76 /* Driver-local specific stuff */
78 struct usb_interface *interface;
81 struct mutex rng_lock;
82 int open; /* open count */
83 int present; /* device not disconnected */
84 int size; /* size of buf */
85 int valid; /* bytes of buf read */
86 int used; /* bytes of buf consumed */
87 char *name; /* product + serial */
88 struct hwrng hwrng; /* Embedded struct for hwrng */
89 int hwrng_registered; /* registered with hwrng API */
90 wait_queue_head_t wait_q; /* for timeouts */
94 static void chaoskey_free(struct chaoskey *dev)
96 usb_dbg(dev->interface, "free");
99 usb_put_intf(dev->interface);
103 static int chaoskey_probe(struct usb_interface *interface,
104 const struct usb_device_id *id)
106 struct usb_device *udev = interface_to_usbdev(interface);
107 struct usb_host_interface *altsetting = interface->cur_altsetting;
110 struct chaoskey *dev;
114 usb_dbg(interface, "probe %s-%s", udev->product, udev->serial);
116 /* Find the first bulk IN endpoint and its packet size */
117 for (i = 0; i < altsetting->desc.bNumEndpoints; i++) {
118 if (usb_endpoint_is_bulk_in(&altsetting->endpoint[i].desc)) {
119 in_ep = usb_endpoint_num(&altsetting->endpoint[i].desc);
120 size = usb_endpoint_maxp(&altsetting->endpoint[i].desc);
125 /* Validate endpoint and size */
127 usb_dbg(interface, "no IN endpoint found");
131 usb_dbg(interface, "invalid size (%d)", size);
135 if (size > CHAOSKEY_BUF_LEN) {
136 usb_dbg(interface, "size reduced from %d to %d\n",
137 size, CHAOSKEY_BUF_LEN);
138 size = CHAOSKEY_BUF_LEN;
141 /* Looks good, allocate and initialize */
143 dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL);
148 dev->interface = usb_get_intf(interface);
150 dev->buf = kmalloc(size, GFP_KERNEL);
152 if (dev->buf == NULL) {
157 /* Construct a name using the product and serial values. Each
158 * device needs a unique name for the hwrng code
161 if (udev->product && udev->serial) {
162 dev->name = kmalloc(strlen(udev->product) + 1 +
163 strlen(udev->serial) + 1, GFP_KERNEL);
164 if (dev->name == NULL) {
170 strcpy(dev->name, udev->product);
171 strcat(dev->name, "-");
172 strcat(dev->name, udev->serial);
180 init_waitqueue_head(&dev->wait_q);
182 mutex_init(&dev->lock);
183 mutex_init(&dev->rng_lock);
185 usb_set_intfdata(interface, dev);
187 result = usb_register_dev(interface, &chaoskey_class);
189 usb_err(interface, "Unable to allocate minor number.");
190 usb_set_intfdata(interface, NULL);
195 dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name;
196 dev->hwrng.read = chaoskey_rng_read;
198 /* Set the 'quality' metric. Quality is measured in units of
199 * 1/1024's of a bit ("mills"). This should be set to 1024,
200 * but there is a bug in the hwrng core which masks it with
203 * The patch that has been merged to the crypto development
204 * tree for that bug limits the value to 1024 at most, so by
205 * setting this to 1024 + 1023, we get 1023 before the fix is
206 * merged and 1024 afterwards. We'll patch this driver once
207 * both bits of code are in the same tree.
209 dev->hwrng.quality = 1024 + 1023;
211 dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0);
212 if (!dev->hwrng_registered)
213 usb_err(interface, "Unable to register with hwrng");
215 usb_enable_autosuspend(udev);
217 usb_dbg(interface, "chaoskey probe success, size %d", dev->size);
221 static void chaoskey_disconnect(struct usb_interface *interface)
223 struct chaoskey *dev;
225 usb_dbg(interface, "disconnect");
226 dev = usb_get_intfdata(interface);
228 usb_dbg(interface, "disconnect failed - no dev");
232 if (dev->hwrng_registered)
233 hwrng_unregister(&dev->hwrng);
235 usb_deregister_dev(interface, &chaoskey_class);
237 usb_set_intfdata(interface, NULL);
238 mutex_lock(&dev->lock);
243 mutex_unlock(&dev->lock);
246 mutex_unlock(&dev->lock);
248 usb_dbg(interface, "disconnect done");
251 static int chaoskey_open(struct inode *inode, struct file *file)
253 struct chaoskey *dev;
254 struct usb_interface *interface;
256 /* get the interface from minor number and driver information */
257 interface = usb_find_interface(&chaoskey_driver, iminor(inode));
261 usb_dbg(interface, "open");
263 dev = usb_get_intfdata(interface);
265 usb_dbg(interface, "open (dev)");
269 file->private_data = dev;
270 mutex_lock(&dev->lock);
272 mutex_unlock(&dev->lock);
274 usb_dbg(interface, "open success");
278 static int chaoskey_release(struct inode *inode, struct file *file)
280 struct chaoskey *dev = file->private_data;
281 struct usb_interface *interface;
286 interface = dev->interface;
288 usb_dbg(interface, "release");
290 mutex_lock(&dev->lock);
292 usb_dbg(interface, "open count at release is %d", dev->open);
294 if (dev->open <= 0) {
295 usb_dbg(interface, "invalid open count (%d)", dev->open);
296 mutex_unlock(&dev->lock);
303 if (dev->open == 0) {
304 mutex_unlock(&dev->lock);
307 mutex_unlock(&dev->lock);
309 mutex_unlock(&dev->lock);
311 usb_dbg(interface, "release success");
315 /* Fill the buffer. Called with dev->lock held
317 static int _chaoskey_fill(struct chaoskey *dev)
322 struct usb_device *udev = interface_to_usbdev(dev->interface);
324 usb_dbg(dev->interface, "fill");
326 /* Return immediately if someone called before the buffer was
328 if (dev->valid != dev->used) {
329 usb_dbg(dev->interface, "not empty yet (valid %d used %d)",
330 dev->valid, dev->used);
334 /* Bail if the device has been removed */
336 usb_dbg(dev->interface, "device not present");
340 /* Make sure the device is awake */
341 result = usb_autopm_get_interface(dev->interface);
343 usb_dbg(dev->interface, "wakeup failed (result %d)", result);
347 result = usb_bulk_msg(udev,
348 usb_rcvbulkpipe(udev, dev->in_ep),
349 dev->buf, dev->size, &this_read,
352 /* Let the device go back to sleep eventually */
353 usb_autopm_put_interface(dev->interface);
356 dev->valid = this_read;
360 usb_dbg(dev->interface, "bulk_msg result %d this_read %d",
366 static ssize_t chaoskey_read(struct file *file,
371 struct chaoskey *dev;
372 ssize_t read_count = 0;
375 unsigned long remain;
377 dev = file->private_data;
379 if (dev == NULL || !dev->present)
382 usb_dbg(dev->interface, "read %zu", count);
386 /* Grab the rng_lock briefly to ensure that the hwrng interface
387 * gets priority over other user access
389 result = mutex_lock_interruptible(&dev->rng_lock);
392 mutex_unlock(&dev->rng_lock);
394 result = mutex_lock_interruptible(&dev->lock);
397 if (dev->valid == dev->used) {
398 result = _chaoskey_fill(dev);
400 mutex_unlock(&dev->lock);
404 /* Read returned zero bytes */
405 if (dev->used == dev->valid) {
406 mutex_unlock(&dev->lock);
411 this_time = dev->valid - dev->used;
412 if (this_time > count)
415 remain = copy_to_user(buffer, dev->buf + dev->used, this_time);
419 /* Consume the bytes that were copied so we don't leak
422 dev->used += this_time - remain;
423 mutex_unlock(&dev->lock);
428 read_count += this_time;
430 dev->used += this_time;
431 mutex_unlock(&dev->lock);
435 usb_dbg(dev->interface, "read %zu bytes", read_count);
438 usb_dbg(dev->interface, "empty read, result %d", result);
442 static int chaoskey_rng_read(struct hwrng *rng, void *data,
443 size_t max, bool wait)
445 struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng);
448 usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait);
451 usb_dbg(dev->interface, "device not present");
455 /* Hold the rng_lock until we acquire the device lock so that
456 * this operation gets priority over other user access to the
459 mutex_lock(&dev->rng_lock);
461 mutex_lock(&dev->lock);
463 mutex_unlock(&dev->rng_lock);
465 /* Try to fill the buffer if empty. It doesn't actually matter
466 * if _chaoskey_fill works; we'll just return zero bytes as
467 * the buffer will still be empty
469 if (dev->valid == dev->used)
470 (void) _chaoskey_fill(dev);
472 this_time = dev->valid - dev->used;
476 memcpy(data, dev->buf + dev->used, this_time);
478 dev->used += this_time;
480 mutex_unlock(&dev->lock);
482 usb_dbg(dev->interface, "rng_read this_time %d\n", this_time);
487 static int chaoskey_suspend(struct usb_interface *interface,
488 pm_message_t message)
490 usb_dbg(interface, "suspend");
494 static int chaoskey_resume(struct usb_interface *interface)
496 usb_dbg(interface, "resume");
500 #define chaoskey_suspend NULL
501 #define chaoskey_resume NULL
504 /* file operation pointers */
505 static const struct file_operations chaoskey_fops = {
506 .owner = THIS_MODULE,
507 .read = chaoskey_read,
508 .open = chaoskey_open,
509 .release = chaoskey_release,
510 .llseek = default_llseek,
513 /* class driver information */
514 static struct usb_class_driver chaoskey_class = {
515 .name = "chaoskey%d",
516 .fops = &chaoskey_fops,
517 .minor_base = USB_CHAOSKEY_MINOR_BASE,
520 /* usb specific object needed to register this driver with the usb subsystem */
521 static struct usb_driver chaoskey_driver = {
522 .name = DRIVER_SHORT,
523 .probe = chaoskey_probe,
524 .disconnect = chaoskey_disconnect,
525 .suspend = chaoskey_suspend,
526 .resume = chaoskey_resume,
527 .reset_resume = chaoskey_resume,
528 .id_table = chaoskey_table,
529 .supports_autosuspend = 1,
532 module_usb_driver(chaoskey_driver);