[PATCH] hwrng: alea - Add support for Araneus Alea I USB RNG

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Adds support for the Araneus Alea I USB hardware Random Number
Generator.  This RNG creates entropy at a high rate, about 100kb/s.

Signed-off-by: Bob Ham <bob.ham@xxxxxxxxxxxxx>
---

Just a note about the name of the module, I haven't append "-rng" to
the name, like every other module in hw_random, because those modules
contain drivers for the RNG part of some more complex device. By
contrast, the Alea is solely an RNG so adding "-rng" to the name seems
redundant.


 drivers/char/hw_random/Kconfig  |  13 ++
 drivers/char/hw_random/Makefile |   1 +
 drivers/char/hw_random/alea.c   | 370 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 384 insertions(+)
 create mode 100644 drivers/char/hw_random/alea.c

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index ac51149..b3f5a89 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -396,6 +396,19 @@ config HW_RANDOM_PIC32
 
 	  If unsure, say Y.
 
+config HW_RANDOM_ALEA
+	tristate "Araneus Alea I USB Random Number Generator support"
+	depends on HW_RANDOM && USB
+	default n
+	---help---
+	  This driver provides kernel-side support for the Araneus
+	  Alea I USB hardware Random Number Generator.
+
+	  To compile this driver as a module, choose M here. the
+	  module will be called alea.
+
+	  If unsure, say N.
+
 endif # HW_RANDOM
 
 config UML_RANDOM
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 63022b4..3709906 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -34,3 +34,4 @@ obj-$(CONFIG_HW_RANDOM_ST) += st-rng.o
 obj-$(CONFIG_HW_RANDOM_XGENE) += xgene-rng.o
 obj-$(CONFIG_HW_RANDOM_STM32) += stm32-rng.o
 obj-$(CONFIG_HW_RANDOM_PIC32) += pic32-rng.o
+obj-$(CONFIG_HW_RANDOM_ALEA) += alea.o
diff --git a/drivers/char/hw_random/alea.c b/drivers/char/hw_random/alea.c
new file mode 100644
index 0000000..50909da
--- /dev/null
+++ b/drivers/char/hw_random/alea.c
@@ -0,0 +1,370 @@
+/*
+ * Copyright (C) 2016 Collabora Ltd
+ * Written by Bob Ham <bob.ham@xxxxxxxxxxxxx>
+ *
+ * An HWRNG driver to pull data from an Araneus Alea I
+ *
+ * derived from:
+ *
+ * USB Skeleton driver - 2.2
+ *
+ * Copyright (C) 2001-2004 Greg Kroah-Hartman (greg@xxxxxxxxx)
+ *
+ *	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.
+ *
+ * This driver is based on the 2.6.3 version of drivers/usb/usb-skeleton.c
+ * but has been rewritten to be easier to read and use.
+ *
+ */
+
+/*
+ * The Alea I is a really simple device.  There is one bulk read
+ * endpoint.  It spits out data in 64-byte chunks.  Each chunk
+ * contains entropy.  Simple.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/kref.h>
+#include <linux/uaccess.h>
+#include <linux/usb.h>
+#include <linux/mutex.h>
+#include <linux/spinlock.h>
+#include <linux/hw_random.h>
+
+
+#define MODULE_NAME "alea"
+
+#define ARANEUS_VENDOR_ID		0x12d8
+#define ARANEUS_ALEA_I_PRODUCT_ID	0x0001
+
+/* table of devices that work with this driver */
+static const struct usb_device_id alea_table[] = {
+	{ USB_DEVICE(ARANEUS_VENDOR_ID, ARANEUS_ALEA_I_PRODUCT_ID) },
+	{ }					/* Terminating entry */
+};
+
+MODULE_DEVICE_TABLE (usb, alea_table);
+
+
+/* Structure to hold all of our device specific stuff */
+struct alea {
+	struct usb_device	*udev;			/* the usb device for this device */
+	struct usb_interface	*interface;		/* the interface for this device */
+	struct urb		*bulk_in_urb;		/* the urb to read data with */
+	unsigned char           *bulk_in_buffer;	/* the buffer to receive data */
+	size_t			bulk_in_size;		/* the size of the receive buffer */
+	size_t			bulk_in_filled;		/* number of bytes in the buffer */
+	__u8			bulk_in_endpointAddr;	/* the address of the bulk in endpoint */
+	int			errors;			/* the last request tanked */
+	bool			ongoing_read;		/* a read is going on */
+	spinlock_t		err_lock;		/* lock for errors */
+	struct kref		kref;
+	struct mutex		io_mutex;		/* synchronize I/O with disconnect */
+	wait_queue_head_t	bulk_in_wait;		/* to wait for an ongoing read */
+	char			*rng_name;		/* name for the hwrng subsystem */
+	struct hwrng		rng;			/* the hwrng info */
+};
+#define kref_to_alea(d) container_of(d, struct alea, kref)
+#define rng_to_alea(d) container_of(d, struct alea, rng)
+
+static struct usb_driver alea_driver;
+
+static void alea_delete(struct kref *kref)
+{
+	struct alea *dev = kref_to_alea(kref);
+
+	kfree(dev->rng_name);
+	usb_free_urb(dev->bulk_in_urb);
+	usb_put_dev(dev->udev);
+	kfree(dev->bulk_in_buffer);
+	kfree(dev);
+}
+
+static void alea_read_callback(struct urb *urb)
+{
+	struct alea *dev = urb->context;
+
+	spin_lock(&dev->err_lock);
+	/* sync/async unlink faults aren't errors */
+	if (urb->status) {
+		if (!(urb->status == -ENOENT ||
+		    urb->status == -ECONNRESET ||
+		    urb->status == -ESHUTDOWN))
+			dev_err(&dev->interface->dev,
+				"%s - nonzero read bulk status received: %d\n",
+				__func__, urb->status);
+
+		dev->errors = urb->status;
+	} else {
+		dev->bulk_in_filled = urb->actual_length;
+	}
+	dev->ongoing_read = 0;
+	spin_unlock(&dev->err_lock);
+
+	wake_up_interruptible(&dev->bulk_in_wait);
+}
+
+static int alea_request_read(struct alea *dev)
+{
+	int rv;
+
+	/* prepare a read */
+	usb_fill_bulk_urb(dev->bulk_in_urb,
+			dev->udev,
+			usb_rcvbulkpipe(dev->udev,
+				dev->bulk_in_endpointAddr),
+			dev->bulk_in_buffer,
+			dev->bulk_in_size,
+			alea_read_callback,
+			dev);
+	/* tell everybody to leave the URB alone */
+	spin_lock_irq(&dev->err_lock);
+	dev->ongoing_read = 1;
+	spin_unlock_irq(&dev->err_lock);
+
+	/* submit bulk in urb, which means no data to deliver */
+	dev->bulk_in_filled = 0;
+
+	/* do it */
+	rv = usb_submit_urb(dev->bulk_in_urb, GFP_KERNEL);
+	if (rv < 0) {
+		dev_err(&dev->interface->dev,
+			"%s - failed submitting read urb, error %d\n",
+			__func__, rv);
+		rv = (rv == -ENOMEM) ? rv : -EIO;
+		spin_lock_irq(&dev->err_lock);
+		dev->ongoing_read = 0;
+		spin_unlock_irq(&dev->err_lock);
+	}
+
+	return rv;
+}
+
+static int alea_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+	struct alea *dev;
+	int rv;
+	bool ongoing_io;
+
+	dev = rng_to_alea(rng);
+
+	/* if we cannot read at all */
+	if (!dev->bulk_in_urb)
+		return 0;
+
+	/* no concurrent readers */
+	rv = mutex_lock_interruptible(&dev->io_mutex);
+	if (rv < 0)
+		return rv;
+
+	if (!dev->interface) {		/* disconnect() was called */
+		rv = -ENODEV;
+		goto exit;
+	}
+
+	/* if IO is under way, we must not touch things */
+retry:
+	spin_lock_irq(&dev->err_lock);
+	ongoing_io = dev->ongoing_read;
+	spin_unlock_irq(&dev->err_lock);
+
+	if (ongoing_io) {
+		if (!wait) {
+			rv = 0;
+			goto exit;
+		}
+
+		/*
+		 * IO may take forever
+		 * hence wait in an interruptible state
+		 */
+		rv = wait_event_interruptible(dev->bulk_in_wait, (!dev->ongoing_read));
+		if (rv < 0)
+			goto exit;
+	}
+
+	/* errors must be reported */
+	rv = dev->errors;
+	if (rv < 0) {
+		/* any error is reported once */
+		dev->errors = 0;
+		/* to preserve notifications about reset */
+		rv = (rv == -EPIPE) ? rv : -EIO;
+		/* report it */
+		goto exit;
+	}
+
+	if (dev->bulk_in_filled) {
+		/* we have data to return */
+		rv = min(dev->bulk_in_filled, max);
+		dev->bulk_in_filled -= rv;
+		memcpy(data, dev->bulk_in_buffer + dev->bulk_in_filled, rv);
+	} else {
+		rv = 0;
+	}
+
+	if (!dev->bulk_in_filled) {
+		/* we need more data */
+		int err;
+
+		err = alea_request_read(dev);
+		if (err < 0) {
+			rv = err;
+			goto exit;
+		}
+
+		/* possibly wait if we haven't copied any data yet */
+		if (!rv && wait)
+			goto retry;
+	}
+exit:
+	mutex_unlock(&dev->io_mutex);
+	return rv;
+}
+
+static int alea_probe(struct usb_interface *interface,
+		      const struct usb_device_id *id)
+{
+	struct alea *dev;
+	struct usb_host_interface *iface_desc;
+	struct usb_endpoint_descriptor *endpoint;
+	int i;
+	int retval = -ENOMEM;
+	char temp_name[1];
+	int name_size;
+
+	/* allocate memory for our device state and initialize it */
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev) {
+		dev_err(&interface->dev, "Out of memory\n");
+		goto error;
+	}
+	kref_init(&dev->kref);
+	mutex_init(&dev->io_mutex);
+	spin_lock_init(&dev->err_lock);
+	init_waitqueue_head(&dev->bulk_in_wait);
+
+	dev->udev = usb_get_dev(interface_to_usbdev(interface));
+	dev->interface = interface;
+
+	dev->rng.read = alea_rng_read;
+
+	/* set up the endpoint information */
+	iface_desc = interface->cur_altsetting;
+	for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
+		endpoint = &iface_desc->endpoint[i].desc;
+
+		if (!usb_endpoint_is_bulk_in(endpoint))
+			continue;
+
+		/* we found our bulk in endpoint */
+		dev->bulk_in_size = usb_endpoint_maxp(endpoint);
+		dev->bulk_in_endpointAddr = endpoint->bEndpointAddress;
+		break;
+	}
+	if (!dev->bulk_in_endpointAddr) {
+		dev_err(&interface->dev,
+			"Could not find endpoint\n");
+		goto error;
+	}
+
+	/* allocate objects */
+	dev->bulk_in_buffer = kmalloc(dev->bulk_in_size, GFP_KERNEL);
+	if (!dev->bulk_in_buffer) {
+		dev_err(&interface->dev,
+			"Could not allocate bulk_in_buffer\n");
+		goto error;
+	}
+	dev->bulk_in_urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!dev->bulk_in_urb) {
+		dev_err(&interface->dev,
+			"Could not allocate bulk_in_urb\n");
+		goto error;
+	}
+
+	/* set name for hwrng */
+	name_size = 1 + snprintf(temp_name, sizeof(temp_name),
+				 "alea-%s", dev_name(&interface->dev));
+	dev->rng_name = kmalloc(name_size, GFP_KERNEL);
+	if (!dev->rng_name) {
+		dev_err(&interface->dev,
+			"Could not allocate rng_name\n");
+		goto error;
+	}
+	snprintf(dev->rng_name, name_size,
+		 "alea-%s", dev_name(&interface->dev));
+	dev->rng.name = &dev->rng_name[0];
+
+	/* save our data pointer in this interface device */
+	usb_set_intfdata(interface, dev);
+
+	/* kick off the first read */
+	retval = alea_request_read(dev);
+	if (retval) {
+		dev_err(&interface->dev,
+			"Could not start first USB read\n");
+		goto error_intf;
+	}
+
+	/* register with hwrng subsystem */
+	retval = devm_hwrng_register(&dev->udev->dev, &dev->rng);
+	if (retval) {
+		dev_err(&interface->dev,
+			"Not able to register RNG for this device.\n");
+		goto error_intf;
+	}
+
+	/* let the user know what node this device is now attached to */
+	dev_info(&interface->dev,
+		 "Araneus Alea I device now attached to RNG %s",
+		 dev->rng_name);
+	return 0;
+
+error_intf:
+	usb_set_intfdata(interface, NULL);
+error:
+	if (dev)
+		/* this frees allocated memory */
+		kref_put(&dev->kref, alea_delete);
+	return retval;
+}
+
+static void alea_disconnect(struct usb_interface *interface)
+{
+	struct alea *dev;
+
+	dev = usb_get_intfdata(interface);
+	usb_set_intfdata(interface, NULL);
+
+	/* remove us from the hwrng subsystem */
+	devm_hwrng_unregister(&dev->udev->dev, &dev->rng);
+
+	/* prevent more I/O from starting */
+	mutex_lock(&dev->io_mutex);
+	dev->interface = NULL;
+	mutex_unlock(&dev->io_mutex);
+
+	dev_info(&interface->dev,
+		 "Araneus Alea I %s now disconnected",
+		 dev->rng_name);
+
+	/* decrement our usage count */
+	kref_put(&dev->kref, alea_delete);
+}
+
+static struct usb_driver alea_driver = {
+	.name =		MODULE_NAME,
+	.probe =	alea_probe,
+	.disconnect =	alea_disconnect,
+	.id_table =	alea_table,
+};
+
+module_usb_driver(alea_driver);
+
+MODULE_LICENSE("GPL");
-- 
2.1.4

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