usb: Add driver for Altus Metrum ChaosKey device

This is a hardware random number generator. The driver provides both a
/dev/chaoskeyX entry and hooks the entropy source up to the kernel
hwrng interface. More information about the device can be found at
http://chaoskey.org

The USB ID for ChaosKey was allocated from the OpenMoko USB vendor
space and is visible as 'USBtrng' here:

http://wiki.openmoko.org/wiki/USB_Product_IDs

Signed-off-by: Keith Packard <keithp-aN4HjG94KOLQT0dZR+AlfA@public.gmane.org>
---
 drivers/usb/misc/Kconfig    |  12 +
 drivers/usb/misc/Makefile   |   1 +
 drivers/usb/misc/chaoskey.c | 550 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 563 insertions(+)
 create mode 100644 drivers/usb/misc/chaoskey.c

diff --git a/drivers/usb/misc/Kconfig b/drivers/usb/misc/Kconfig
index 76d7720..8c331f1 100644
--- a/drivers/usb/misc/Kconfig
+++ b/drivers/usb/misc/Kconfig
@@ -255,3 +255,15 @@ config USB_LINK_LAYER_TEST
 	  This driver is for generating specific traffic for Super Speed Link
 	  Layer Test Device. Say Y only when you want to conduct USB Super Speed
 	  Link Layer Test for host controllers.
+
+config USB_CHAOSKEY
+	tristate "ChaosKey random number generator driver support"
+	help
+	  Say Y here if you want to connect an AltusMetrum ChaosKey to
+	  your computer's USB port. The ChaosKey is a hardware random
+	  number generator which hooks into the kernel entropy pool to
+	  ensure a large supply of entropy for /dev/random and
+	  /dev/urandom and also provides direct access via /dev/chaoskeyX
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called chaoskey.
diff --git a/drivers/usb/misc/Makefile b/drivers/usb/misc/Makefile
index 65b0402..45fd4ac 100644
--- a/drivers/usb/misc/Makefile
+++ b/drivers/usb/misc/Makefile
@@ -25,6 +25,7 @@ obj-$(CONFIG_USB_USS720)		+= uss720.o
 obj-$(CONFIG_USB_SEVSEG)		+= usbsevseg.o
 obj-$(CONFIG_USB_YUREX)			+= yurex.o
 obj-$(CONFIG_USB_HSIC_USB3503)		+= usb3503.o
+obj-$(CONFIG_USB_CHAOSKEY)		+= chaoskey.o
 
 obj-$(CONFIG_USB_SISUSBVGA)		+= sisusbvga/
 obj-$(CONFIG_USB_LINK_LAYER_TEST)	+= lvstest.o
diff --git a/drivers/usb/misc/chaoskey.c b/drivers/usb/misc/chaoskey.c
new file mode 100644
index 0000000..5b32e84
--- /dev/null
+++ b/drivers/usb/misc/chaoskey.c
@@ -0,0 +1,550 @@
+/*
+ * chaoskey - driver for ChaosKey device from Altus Metrum.
+ *
+ * This device provides true random numbers using a noise source based
+ * on a reverse-biased p-n junction in avalanche breakdown. More
+ * details can be found at http://chaoskey.org
+ *
+ * The driver connects to the kernel hardware RNG interface to provide
+ * entropy for /dev/random and other kernel activities. It also offers
+ * a separate /dev/ entry to allow for direct access to the random
+ * bit stream.
+ *
+ * Copyright © 2015 Keith Packard <keithp-aN4HjG94KOLQT0dZR+AlfA@public.gmane.org>
+ *
+ * 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; version 2 of the License.
+ *
+ * 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.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/usb.h>
+#include <linux/wait.h>
+#include <linux/hw_random.h>
+
+#define DEBUG_INIT	1
+#define DEBUG_POWER	2
+#define DEBUG_DEV	4
+#define DEBUG_RNG	8
+#define DEBUG_IO	(DEBUG_DEV|DEBUG_RNG)
+#define DEBUG_API	16
+
+static int debug = 0;	/* bitmask of above values */
+
+static struct usb_driver chaoskey_driver;
+static struct usb_class_driver chaoskey_class;
+static int chaoskey_rng_read(struct hwrng *rng, void *data, size_t max, bool wait);
+
+#define CK_DEBUG(mask, fmt, args...) do {				\
+		if (unlikely(debug & (mask)))				\
+			printk(KERN_INFO " chaoskey: %s: %d " fmt, __func__, __LINE__, ##args); \
+	} while (0)
+
+#define CK_ENTER(mask, what)		CK_DEBUG(mask, "Enter " what)
+#define CK_LEAVE(mask, what,fmt,ret)	CK_DEBUG(mask, "Leave " what ":" fmt, ret)
+#define CK_LEAVE_INT(mask, what,ret)	CK_LEAVE(mask, what,"%d",ret)
+#define CK_LEAVE_SIZE(mask, what,ret)	CK_LEAVE(mask, what,"%zu",ret)
+#define CK_LEAVE_SSIZE(mask, what,ret)	CK_LEAVE(mask, what,"%zd",ret)
+#define CK_LEAVE_VOID(mask, what)	CK_DEBUG(mask, "Leave " what)
+
+/* Version Information */
+#define DRIVER_VERSION	"v0.1"
+#define DRIVER_AUTHOR	"Keith Packard, keithp-aN4HjG94KOLQT0dZR+AlfA@public.gmane.org"
+#define DRIVER_DESC	"Altus Metrum ChaosKey driver"
+#define DRIVER_SHORT	"chaoskey"
+
+MODULE_VERSION(DRIVER_VERSION);
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+MODULE_PARM_DESC(debug, "Enable debug output");
+
+module_param(debug, int, 0644);
+
+#define CHAOSKEY_VENDOR_ID	0x1d50	/* OpenMoko */
+#define CHAOSKEY_PRODUCT_ID	0x60c6	/* ChaosKey */
+
+#define CHAOSKEY_BUF_LEN	64	/* maximum size of USB full speed packet */
+
+#define NAK_TIMEOUT (HZ)		/* stall/wait timeout for device */
+
+#ifdef CONFIG_USB_DYNAMIC_MINORS
+#define USB_CHAOSKEY_MINOR_BASE 0
+#else
+#define USB_CHAOSKEY_MINOR_BASE 224	/* IOWARRIOR_MINOR_BASE + 16, not official yet */
+#endif
+
+static const struct usb_device_id chaoskey_table[] = {
+	{ USB_DEVICE(CHAOSKEY_VENDOR_ID, CHAOSKEY_PRODUCT_ID) },
+	{ },
+};
+MODULE_DEVICE_TABLE (usb, chaoskey_table);
+
+/* Driver-local specific stuff */
+struct chaoskey {
+	struct usb_device *udev;
+	struct usb_interface *interface;
+        char in_ep;
+	struct mutex lock;
+	struct mutex rng_lock;
+	int open;			/* open count */
+	int present;			/* device not disconnected */
+	int size;			/* size of buf */
+	int valid;			/* bytes of buf read */
+	int used;			/* bytes of buf consumed */
+	char *name;			/* product + serial */
+	struct hwrng hwrng;		/* Embedded struct for hwrng */
+	int hwrng_registered;		/* registered with hwrng API */
+        wait_queue_head_t wait_q;	/* for timeouts */
+	char buf[0];
+};
+
+static void chaoskey_free(struct chaoskey *dev)
+{
+	CK_ENTER(DEBUG_INIT, "free");
+	if (dev->name)
+		kfree(dev->name);
+	kfree(dev);
+	CK_LEAVE_VOID(DEBUG_INIT, "free");
+}
+
+static int chaoskey_probe(struct usb_interface *interface,
+			  const struct usb_device_id *id)
+{
+	struct usb_device *udev = interface_to_usbdev(interface);
+	struct usb_host_interface *altsetting = interface->cur_altsetting;
+	int i;
+	int in_ep = -1;
+	struct chaoskey *dev;
+	int result;
+	int size;
+
+	CK_ENTER(DEBUG_INIT, "probe");
+
+	/* Find the first bulk IN endpoint and its packet size */
+	for (i = 0; i < altsetting->desc.bNumEndpoints; i++) {
+		if (usb_endpoint_is_bulk_in(&altsetting->endpoint[i].desc)) {
+			in_ep = altsetting->endpoint[i].desc.bEndpointAddress;
+			size = altsetting->endpoint[i].desc.wMaxPacketSize;
+			break;
+		}
+	}
+
+	/* Validate endpoint and size */
+	if (in_ep == -1) {
+                CK_LEAVE_INT(DEBUG_INIT, "probe (ep)", -ENODEV);
+		return -ENODEV;
+	}
+	if (size <= 0) {
+		CK_LEAVE_INT(DEBUG_INIT, "probe (size)", -ENODEV);
+		return -ENODEV;
+	}
+
+	/* Looks good, allocate and initialize */
+	CK_DEBUG(DEBUG_INIT, "New chaoskey, in_ep %d size %d\n", in_ep, size);
+
+	dev = kzalloc (sizeof (struct chaoskey) + size, GFP_KERNEL);
+
+	if (dev == NULL) {
+		CK_LEAVE_INT(DEBUG_INIT, "probe (dev)", -ENOMEM);
+		return -ENOMEM;
+	}
+
+	dev->udev = udev;
+	dev->interface = interface;
+
+	dev->in_ep = in_ep;
+
+	if (size > CHAOSKEY_BUF_LEN) {
+                CK_DEBUG(DEBUG_INIT, "chaoskey size %d reduced to %d\n", size,
+                         CHAOSKEY_BUF_LEN);
+		size = CHAOSKEY_BUF_LEN;
+        }
+
+	dev->size = size;
+	dev->present = 1;
+
+	init_waitqueue_head(&dev->wait_q);
+
+	usb_set_intfdata(interface, dev);
+
+	result = usb_register_dev(interface, &chaoskey_class);
+	if (result) {
+		dev_err(&interface->dev, "Unable to allocate minor number.\n");
+		usb_set_intfdata(interface, NULL);
+		chaoskey_free(dev);
+		CK_LEAVE_INT(DEBUG_INIT, "probe (register)", result);
+		return result;
+	}
+
+	mutex_init(&dev->lock);
+	mutex_init(&dev->rng_lock);
+
+	/* Construct a name using the product and serial values. Each
+	 * device needs a unique name for the hwrng code
+	 */
+	dev->name = NULL;
+
+	if (udev->product && udev->serial) {
+		dev->name = kmalloc(strlen(udev->product) + 1 + strlen(udev->serial) + 1, GFP_KERNEL);
+		if (dev->name) {
+			strcpy(dev->name, udev->product);
+			strcat(dev->name, "-");
+			strcat(dev->name, udev->serial);
+		}
+	}
+
+	dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name;
+	dev->hwrng.read = chaoskey_rng_read;
+
+	/* Set the 'quality' metric.  Quality is measured in units of
+	 * 1/1024's of a bit ("mills"). This should be set to 1024,
+	 * but there is a bug in the hwrng core which masks it with
+	 * 1023.
+	 *
+	 * The patch that has been merged to the crypto development
+	 * tree for that bug limits the value to 1024 at most, so by
+	 * setting this to 1024 + 1023, we get 1023 before the fix is
+	 * merged and 1024 afterwards. We'll patch this driver once
+	 * both bits of code are in the same tree.
+	 */
+	dev->hwrng.quality = 1024 + 1023;
+
+	dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0);
+        if (!dev->hwrng_registered)
+                CK_DEBUG(DEBUG_INIT, "probe hwrng register failed: %d\n", result);
+
+	usb_enable_autosuspend(udev);
+
+	CK_LEAVE_INT(DEBUG_INIT, "probe", 0);
+	return 0;
+}
+
+static void chaoskey_disconnect(struct usb_interface *interface)
+{
+	struct chaoskey	*dev;
+
+	CK_ENTER(DEBUG_INIT, "disconnect");
+	dev = usb_get_intfdata(interface);
+	if (!dev) {
+		CK_LEAVE_VOID(DEBUG_INIT, "disconnect (dev)");
+		return;
+	}
+
+	if (dev->hwrng_registered)
+		hwrng_unregister(&dev->hwrng);
+
+	usb_deregister_dev(interface, &chaoskey_class);
+
+	usb_set_intfdata(interface, NULL);
+	mutex_lock(&dev->lock);
+
+	dev->present = 0;
+
+	if (!dev->open) {
+		mutex_unlock(&dev->lock);
+		chaoskey_free(dev);
+	} else
+		mutex_unlock(&dev->lock);
+
+	CK_LEAVE_VOID(DEBUG_INIT, "disconnect");
+	return;
+}
+
+static int chaoskey_open(struct inode *inode, struct file *file)
+{
+	struct chaoskey *dev;
+	struct usb_interface *interface;
+
+        CK_ENTER(DEBUG_DEV, "open");
+	/* get the interface from minor number and driver information */
+	interface = usb_find_interface (&chaoskey_driver, iminor (inode));
+	if (!interface) {
+                CK_LEAVE_INT(DEBUG_DEV, "open (interface)", -ENODEV);
+		return -ENODEV;
+        }
+
+	dev = usb_get_intfdata(interface);
+	if (!dev) {
+                CK_LEAVE_INT(DEBUG_DEV, "open (dev)", -ENODEV);
+		return -ENODEV;
+        }
+
+	file->private_data = dev;
+	mutex_lock(&dev->lock);
+	++dev->open;
+	mutex_unlock(&dev->lock);
+
+        CK_LEAVE_INT(DEBUG_DEV, "open", 0);
+	return 0;
+}
+
+static int chaoskey_release(struct inode *inode, struct file *file)
+{
+	struct chaoskey *dev = file->private_data;
+
+	CK_ENTER(DEBUG_DEV, "release");
+
+	if (dev == NULL) {
+		CK_LEAVE_INT(DEBUG_DEV, "release (dev)", -ENODEV);
+		return -ENODEV;
+	}
+
+	mutex_lock(&dev->lock);
+
+	CK_DEBUG(DEBUG_DEV, "open count %d\n", dev->open);
+
+	if (dev->open <= 0) {
+		mutex_unlock(&dev->lock);
+		CK_LEAVE_INT(DEBUG_DEV, "release (open)", -ENODEV);
+		return -ENODEV;
+	}
+
+	--dev->open;
+
+	if (!dev->present) {
+		if (dev->open == 0) {
+			mutex_unlock(&dev->lock);
+			chaoskey_free(dev);
+		} else
+			mutex_unlock(&dev->lock);
+	} else
+		mutex_unlock(&dev->lock);
+
+	CK_LEAVE_INT(DEBUG_DEV, "release", 0);
+	return 0;
+}
+
+/* Fill the buffer. Called with dev->lock held
+ */
+static int _chaoskey_fill(struct chaoskey *dev)
+{
+	DEFINE_WAIT(wait);
+	int result;
+	int this_read;
+
+	CK_ENTER(DEBUG_IO, "fill");
+
+	/* Return immediately if someone called before the buffer was
+	 * empty */
+	if (dev->valid != dev->used) {
+                CK_LEAVE_INT(DEBUG_IO, "fill (valid)", 0);
+		return 0;
+	}
+
+	/* Bail if the device has been removed */
+	if (!dev->present) {
+		CK_LEAVE_INT(DEBUG_IO, "fill (present)", -ENODEV);
+		return -ENODEV;
+	}
+
+	/* Make sure the device is awake */
+	result = usb_autopm_get_interface(dev->interface);
+	if (result) {
+		CK_LEAVE_INT(DEBUG_IO, "fill (interface)", result);
+		return result;
+	}
+
+	result = usb_bulk_msg(dev->udev,
+			      usb_rcvbulkpipe(dev->udev, dev->in_ep),
+			      dev->buf, dev->size, &this_read,
+			      NAK_TIMEOUT);
+
+	/* Let the device go back to sleep eventually */
+	usb_autopm_put_interface(dev->interface);
+
+	CK_DEBUG(DEBUG_IO, "bulk msg result %d partial %d", result, this_read);
+
+	if (result == 0) {
+		dev->valid = this_read;
+		dev->used = 0;
+	}
+
+	CK_LEAVE_INT(DEBUG_IO, "fill", result);
+	return result;
+}
+
+static ssize_t chaoskey_read(struct file *file,
+			     char __user *buffer,
+			     size_t count,
+			     loff_t * ppos)
+{
+	struct chaoskey *dev;
+	int intr;
+	ssize_t read_count = 0;
+	int this_time;
+	int result;
+
+	CK_ENTER(DEBUG_DEV, "read");
+	dev = file->private_data;
+
+	if (dev == NULL || !dev->present) {
+		CK_LEAVE_INT(DEBUG_DEV, "read (present)", -ENODEV);
+		return -ENODEV;
+	}
+
+
+	CK_DEBUG(DEBUG_DEV, "read %zu\n", count);
+
+	while (count > 0) {
+
+		/* Grab the rng_lock briefly to ensure that the hwrng interface
+		 * gets priority over other user access
+		 */
+		intr = mutex_lock_interruptible(&dev->rng_lock);
+		if (intr) {
+			CK_LEAVE_INT(DEBUG_DEV, "read (rng_lock)", -EINTR);
+			return -EINTR;
+		}
+		mutex_unlock(&dev->rng_lock);
+
+		intr = mutex_lock_interruptible(&dev->lock);
+		if (intr) {
+			CK_LEAVE_INT(DEBUG_DEV, "read (lock)", -EINTR);
+			return -EINTR;
+		}
+		if (dev->valid == dev->used) {
+			result = _chaoskey_fill(dev);
+			if (result) {
+				if (read_count) {
+					CK_LEAVE_SIZE(DEBUG_DEV, "read (count)",
+                                                      read_count);
+					return read_count;
+				}
+				CK_LEAVE_INT(DEBUG_DEV, "read (result)", result);
+				return result;
+			}
+
+			/* Read returned zero bytes */
+			if (dev->used == dev->valid) {
+				CK_LEAVE_SSIZE(DEBUG_DEV, "read (zero)", read_count);
+				return read_count;
+			}
+		}
+
+		this_time = dev->valid - dev->used;
+		if (this_time > count)
+			this_time = count;
+
+		if (copy_to_user(buffer, dev->buf + dev->used, this_time)) {
+                        mutex_unlock(&dev->lock);
+                        CK_LEAVE_INT(DEBUG_DEV, "read (copyout)", -EFAULT);
+                        return -EFAULT;
+		}
+
+		count -= this_time;
+		read_count += this_time;
+		buffer += this_time;
+		dev->used += this_time;
+		mutex_unlock(&dev->lock);
+	}
+
+        CK_LEAVE_SSIZE(DEBUG_DEV, "read", read_count);
+	return read_count;
+}
+
+static int chaoskey_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+	struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng);
+	int result;
+	int this_time;
+
+	CK_ENTER(DEBUG_RNG, "rng_read");
+	if (dev == NULL || !dev->present) {
+		CK_LEAVE_INT(DEBUG_RNG, "rng_read (dev)", 0);
+		return 0;
+	}
+
+	/* Hold the rng_lock until we acquire the device lock so that
+	 * this operation gets priority over other user access to the
+	 * device
+	 */
+	mutex_lock(&dev->rng_lock);
+
+	mutex_lock(&dev->lock);
+
+	mutex_unlock(&dev->rng_lock);
+
+	CK_DEBUG(DEBUG_RNG, "rng_read max %zu wait %d\n", max, wait);
+
+	if (dev->valid == dev->used) {
+		result = _chaoskey_fill(dev);
+		if (result) {
+			mutex_unlock(&dev->lock);
+                        CK_LEAVE_INT(DEBUG_RNG, "rng_read (fill)", 0);
+			return 0;
+		}
+	}
+
+	this_time = dev->valid - dev->used;
+
+	if (this_time > max)
+		this_time = max;
+
+	memcpy(data, dev->buf, this_time);
+
+	dev->used += this_time;
+
+	mutex_unlock(&dev->lock);
+
+        CK_LEAVE_INT(DEBUG_RNG, "read", this_time);
+	return this_time;
+}
+
+#ifdef CONFIG_PM
+static int chaoskey_suspend(struct usb_interface *intf, pm_message_t message)
+{
+        CK_DEBUG(DEBUG_POWER, "suspend");
+	return 0;
+}
+
+static int chaoskey_resume(struct usb_interface *intf)
+{
+        CK_DEBUG(DEBUG_POWER, "resume");
+	return 0;
+}
+#else
+#define chaoskey_suspend NULL
+#define chaoskey_resume NULL
+#endif
+
+/* file operation pointers */
+static const struct file_operations chaoskey_fops = {
+	.owner = THIS_MODULE,
+	.read = chaoskey_read,
+	.open = chaoskey_open,
+	.release = chaoskey_release,
+	.llseek = default_llseek,
+};
+
+/* class driver information */
+static struct usb_class_driver chaoskey_class = {
+	.name = "chaoskey%d",
+	.fops = &chaoskey_fops,
+	.minor_base = USB_CHAOSKEY_MINOR_BASE,
+};
+
+/* usb specific object needed to register this driver with the usb subsystem */
+static struct usb_driver chaoskey_driver = {
+	.name = DRIVER_SHORT,
+	.probe = chaoskey_probe,
+	.disconnect = chaoskey_disconnect,
+	.suspend = chaoskey_suspend,
+	.resume = chaoskey_resume,
+	.reset_resume = chaoskey_resume,
+	.id_table = chaoskey_table,
+	.supports_autosuspend = 1,
+};
+
+module_usb_driver(chaoskey_driver);
+
-- 
2.1.4

--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html