usb: Add driver for Altus Metrum ChaosKey device (v2)

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

v2: Respond to review from Oliver Neukum <oneukum@suse.de>

 * Delete extensive debug infrastructure and replace it with calls to
   dev_dbg.

 * Allocate I/O buffer separately from device structure to obey
   requirements for non-coherant architectures.

 * Initialize mutexes before registering device to ensure that open
   cannot be invoked before the device is ready to proceed.

 * Return number of bytes read instead of -EINTR when partial read
   operation is aborted due to a signal.

 * Make sure device mutex is unlocked in read error paths.

 * Add MAINTAINERS entry for the driver

Signed-off-by: Keith Packard <keithp@keithp.com>
Cc: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/usb/misc/Kconfig b/drivers/usb/misc/Kconfig
index 76d77206e011..8c331f1dfd23 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.