[PATCH] Staging : Add RIFFA PCIe driver

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This patch adds RIFFA PCIe linux driver for https://github.com/promach/riffa/tree/full_duplex/driver/linux 
This staging driver is modified from this upstream driver at https://github.com/KastnerRG/riffa/tree/master/driver/linux

Signed-off-by: PHUNG CHENG FEI <feiphung@xxxxxxxxxxx>

---
Changes in v1:
  - added full-duplex capability


 drivers/staging/riffa/Kconfig        |    5 +
 drivers/staging/riffa/Makefile       |    1 +
 drivers/staging/riffa/TODO           |    6 +
 drivers/staging/riffa/circ_queue.c   |  195 +++
 drivers/staging/riffa/circ_queue.h   |   96 ++
 drivers/staging/riffa/riffa.c        |  151 +++
 drivers/staging/riffa/riffa.h        |  121 ++
 drivers/staging/riffa/riffa_driver.c | 1881 ++++++++++++++++++++++++++
 drivers/staging/riffa/riffa_driver.h |  125 ++
 9 files changed, 2581 insertions(+)
 create mode 100644 drivers/staging/riffa/Kconfig
 create mode 100644 drivers/staging/riffa/Makefile
 create mode 100644 drivers/staging/riffa/TODO
 create mode 100644 drivers/staging/riffa/circ_queue.c
 create mode 100644 drivers/staging/riffa/circ_queue.h
 create mode 100644 drivers/staging/riffa/riffa.c
 create mode 100644 drivers/staging/riffa/riffa.h
 create mode 100644 drivers/staging/riffa/riffa_driver.c
 create mode 100644 drivers/staging/riffa/riffa_driver.h

diff --git a/drivers/staging/riffa/Kconfig b/drivers/staging/riffa/Kconfig
new file mode 100644
index 000000000000..afe5beee1882
--- /dev/null
+++ b/drivers/staging/riffa/Kconfig
@@ -0,0 +1,5 @@
+config RIFFA_PCIE
+    tristate "a simple framework for communicating data from a host CPU to a FPGA via a PCI Express bus"
+    default n
+    help
+        Transfers data with full duplex capability using PCIe protocol
diff --git a/drivers/staging/riffa/Makefile b/drivers/staging/riffa/Makefile
new file mode 100644
index 000000000000..79ef3b9b8c8f
--- /dev/null
+++ b/drivers/staging/riffa/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_RIFFA) += riffa.o circ_queue.o riffa_driver.o riffa_mod.o
diff --git a/drivers/staging/riffa/TODO b/drivers/staging/riffa/TODO
new file mode 100644
index 000000000000..0088eef3b282
--- /dev/null
+++ b/drivers/staging/riffa/TODO
@@ -0,0 +1,6 @@
+TODO:
+- optimize the driver code for further speed improvement although it can now achieve defined PCIe speed grade
+- solve all the coding style errors from scripts/checkpatch.pl
+
+Please send any patches to Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
+and Phung Cheng Fei <feiphung@xxxxxxxxxxx>
diff --git a/drivers/staging/riffa/circ_queue.c b/drivers/staging/riffa/circ_queue.c
new file mode 100644
index 000000000000..97ac856bab95
--- /dev/null
+++ b/drivers/staging/riffa/circ_queue.c
@@ -0,0 +1,195 @@
+// ----------------------------------------------------------------------
+// Copyright (c) 2016, The Regents of the University of California All
+// rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//
+//     * Neither the name of The Regents of the University of California
+//       nor the names of its contributors may be used to endorse or
+//       promote products derived from this software without specific
+//       prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL REGENTS OF THE
+// UNIVERSITY OF CALIFORNIA BE LIABLE FOR ANY DIRECT, INDIRECT,
+// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+// OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+// TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+// USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+// DAMAGE.
+// ----------------------------------------------------------------------
+
+/*
+ * Filename: circ_queue.c
+ * Version: 1.0
+ * Description: A lock-free single-producer circular queue implementation 
+ *   modeled after the more elaborate C++ version from Faustino Frechilla at:
+ *   http://www.codeproject.com/Articles/153898/Yet-another-implementation-of-a-lock-free-circular
+ * Author: Matthew Jacobsen
+ * History: @mattj: Initial release. Version 1.0.
+ */
+
+#include <linux/slab.h>
+#include "circ_queue.h"
+
+circ_queue *init_circ_queue(int len)
+{
+	int i;
+	circ_queue *q;
+
+	q = kzalloc(sizeof(circ_queue), GFP_KERNEL);
+	if (q == NULL) {
+		printk(KERN_ERR "Not enough memory to allocate circ_queue");
+		return NULL;
+	}
+
+	atomic_set(&q->writeIndex, 0);
+	atomic_set(&q->readIndex, 0);
+	q->len = len;
+
+	q->vals = (unsigned int **)kzalloc(len * sizeof(unsigned int *),
+					   GFP_KERNEL);
+	if (q->vals == NULL) {
+		printk(KERN_ERR
+		       "Not enough memory to allocate circ_queue array");
+		return NULL;
+	}
+	for (i = 0; i < len; i++) {
+		q->vals[i] = (unsigned int *)kzalloc(2 * sizeof(unsigned int),
+						     GFP_KERNEL);
+		if (q->vals[i] == NULL) {
+			printk(KERN_ERR
+			       "Not enough memory to allocate circ_queue array position");
+			return NULL;
+		}
+	}
+
+	return q;
+}
+
+/**
+ * Internal function to help count. Returns the queue size normalized position.
+ */
+unsigned int queue_count_to_index(unsigned int count, unsigned int len)
+{
+	return (count % len);
+}
+
+int push_circ_queue(circ_queue *q, unsigned int val1, unsigned int val2)
+{
+	unsigned int currReadIndex;
+	unsigned int currWriteIndex;
+
+	currWriteIndex = atomic_read(&q->writeIndex);
+	currReadIndex = atomic_read(&q->readIndex);
+	if (queue_count_to_index(currWriteIndex + 1, q->len) ==
+	    queue_count_to_index(currReadIndex, q->len)) {
+		// The queue is full
+		return 1;
+	}
+
+	// Save the data into the queue
+	q->vals[queue_count_to_index(currWriteIndex, q->len)][0] = val1;
+	q->vals[queue_count_to_index(currWriteIndex, q->len)][1] = val2;
+	// Increment atomically write index. Now a consumer thread can read
+	// the piece of data that was just stored.
+	atomic_inc(&q->writeIndex);
+
+	return 0;
+}
+
+int pop_circ_queue(circ_queue *q, unsigned int *val1, unsigned int *val2)
+{
+	unsigned int currReadIndex;
+	unsigned int currMaxReadIndex;
+
+	do {
+		currReadIndex = atomic_read(&q->readIndex);
+		currMaxReadIndex = atomic_read(&q->writeIndex);
+		if (queue_count_to_index(currReadIndex, q->len) ==
+		    queue_count_to_index(currMaxReadIndex, q->len)) {
+			// The queue is empty or a producer thread has allocate space in the queue
+			// but is waiting to commit the data into it
+			return 1;
+		}
+
+		// Retrieve the data from the queue
+		*val1 = q->vals[queue_count_to_index(currReadIndex, q->len)][0];
+		*val2 = q->vals[queue_count_to_index(currReadIndex, q->len)][1];
+
+		// Try to perfrom now the CAS operation on the read index. If we succeed
+		// label & val already contain what q->readIndex pointed to before we
+		// increased it.
+		if (atomic_cmpxchg(&q->readIndex, currReadIndex,
+				   currReadIndex + 1) == currReadIndex) {
+			// The lable & val were retrieved from the queue. Note that the
+			// data inside the label or value arrays are not deleted.
+			return 0;
+		}
+
+		// Failed to retrieve the elements off the queue. Someone else must
+		// have read the element stored at countToIndex(currReadIndex)
+		// before we could perform the CAS operation.
+	} while (1); // keep looping to try again!
+
+	return 1;
+}
+
+int circ_queue_empty(circ_queue *q)
+{
+	unsigned int currReadIndex;
+	unsigned int currMaxReadIndex;
+
+	currReadIndex = atomic_read(&q->readIndex);
+	currMaxReadIndex = atomic_read(&q->writeIndex);
+	if (queue_count_to_index(currReadIndex, q->len) ==
+	    queue_count_to_index(currMaxReadIndex, q->len)) {
+		// The queue is empty or a producer thread has allocate space in the queue
+		// but is waiting to commit the data into it
+		return 1;
+	}
+	return 0;
+}
+
+int circ_queue_full(circ_queue *q)
+{
+	unsigned int currReadIndex;
+	unsigned int currWriteIndex;
+
+	currWriteIndex = atomic_read(&q->writeIndex);
+	currReadIndex = atomic_read(&q->readIndex);
+	if (queue_count_to_index(currWriteIndex + 1, q->len) ==
+	    queue_count_to_index(currReadIndex, q->len)) {
+		// The queue is full
+		return 1;
+	}
+	return 0;
+}
+
+void free_circ_queue(circ_queue *q)
+{
+	int i;
+
+	if (q == NULL)
+		return;
+
+	for (i = 0; i < q->len; i++) {
+		kfree(q->vals[i]);
+	}
+	kfree(q->vals);
+	kfree(q);
+}
diff --git a/drivers/staging/riffa/circ_queue.h b/drivers/staging/riffa/circ_queue.h
new file mode 100644
index 000000000000..6299fa801512
--- /dev/null
+++ b/drivers/staging/riffa/circ_queue.h
@@ -0,0 +1,96 @@
+// ----------------------------------------------------------------------
+// Copyright (c) 2016, The Regents of the University of California All
+// rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//
+//     * Neither the name of The Regents of the University of California
+//       nor the names of its contributors may be used to endorse or
+//       promote products derived from this software without specific
+//       prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL REGENTS OF THE
+// UNIVERSITY OF CALIFORNIA BE LIABLE FOR ANY DIRECT, INDIRECT,
+// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+// OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+// TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+// USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+// DAMAGE.
+// ----------------------------------------------------------------------
+
+/*
+ * Filename: circ_queue.h
+ * Version: 1.0
+ * Description: A lock-free single-producer circular queue implementation 
+ *   modeled after the more elaborate C++ version from Faustino Frechilla at:
+ *   http://www.codeproject.com/Articles/153898/Yet-another-implementation-of-a-lock-free-circular
+ * Author: Matthew Jacobsen
+ * History: @mattj: Initial release. Version 1.0.
+ */
+#ifndef CIRC_QUEUE_H
+#define CIRC_QUEUE_H
+
+#include <asm/atomic.h>
+
+/* Struct for the circular queue. */
+struct circ_queue {
+	atomic_t writeIndex;
+	atomic_t readIndex;
+	unsigned int **vals;
+	unsigned int len;
+};
+typedef struct circ_queue circ_queue;
+
+/**
+ * Initializes a circ_queue with depth/length len. Returns non-NULL on success, 
+ * NULL if there was a problem creating the queue.
+ */
+circ_queue *init_circ_queue(int len);
+
+/**
+ * Pushes a pair of unsigned int values into the specified queue at the head. 
+ * Returns 0 on success, non-zero if there is no more space in the queue.
+ */
+int push_circ_queue(circ_queue *q, unsigned int val1, unsigned int val2);
+
+/**
+ * Pops a pair of unsigned int values out of the specified queue from the tail.
+ * Returns 0 on success, non-zero if the queue is empty.
+ */
+int pop_circ_queue(circ_queue *q, unsigned int *val1, unsigned int *val2);
+
+/**
+ * Returns 1 if the circ_queue is empty, 0 otherwise. Note, this is not a 
+ * synchronized function. If another thread is accessing this circ_queue, the
+ * return value may not be valid.
+ */
+int circ_queue_empty(circ_queue *q);
+
+/**
+ * Returns 1 if the circ_queue is full, 0 otherwise. Note, this is not a 
+ * synchronized function. If another thread is accessing this circ_queue, the
+ * return value may not be valid.
+ */
+int circ_queue_full(circ_queue *q);
+
+/**
+ * Frees the resources associated with the specified circ_queue.
+ */
+void free_circ_queue(circ_queue *q);
+
+#endif
diff --git a/drivers/staging/riffa/riffa.c b/drivers/staging/riffa/riffa.c
new file mode 100644
index 000000000000..5a87a05009eb
--- /dev/null
+++ b/drivers/staging/riffa/riffa.c
@@ -0,0 +1,151 @@
+// ----------------------------------------------------------------------
+// Copyright (c) 2016, The Regents of the University of California All
+// rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//
+//     * Neither the name of The Regents of the University of California
+//       nor the names of its contributors may be used to endorse or
+//       promote products derived from this software without specific
+//       prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL REGENTS OF THE
+// UNIVERSITY OF CALIFORNIA BE LIABLE FOR ANY DIRECT, INDIRECT,
+// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+// OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+// TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+// USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+// DAMAGE.
+// ----------------------------------------------------------------------
+
+/*
+ * Filename: riffa.c
+ * Version: 2.0
+ * Description: Linux PCIe communications API for RIFFA.
+ * Author: Matthew Jacobsen
+ * History: @mattj: Initial release. Version 2.0.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <fcntl.h>
+#include "riffa.h"
+
+struct thread_info { /* Used as argument to thread_start() */
+	// please refer to API of fpga_send() and fpga_recv() at http://riffa.ucsd.edu/node/10 or https://github.com/KastnerRG/riffa/blob/master/driver/linux/riffa.c#L84-L111
+	fpga_t *fpga;
+	unsigned int chnl;
+	unsigned int *buffer;
+	unsigned int len;
+	unsigned int offset;
+	unsigned int last;
+	long long timeout;
+};
+
+struct fpga_t {
+	int fd;
+	int id;
+};
+
+fpga_t *fpga_open(int id)
+{
+	fpga_t *fpga;
+
+	// Allocate space for the fpga_dev
+	fpga = (fpga_t *)malloc(sizeof(fpga_t));
+	if (fpga == NULL)
+		return NULL;
+	fpga->id = id;
+
+	// Open the device file.
+	fpga->fd = open("/dev/" DEVICE_NAME, O_RDWR | O_SYNC);
+	if (fpga->fd < 0) {
+		free(fpga);
+		return NULL;
+	}
+
+	return fpga;
+}
+
+void fpga_close(fpga_t *fpga)
+{
+	// Close the device file.
+	close(fpga->fd);
+	free(fpga);
+}
+
+//int fpga_send(fpga_t * fpga, int chnl, void * data, int len, int destoff, int last, long long timeout)
+void *fpga_send(void *arg)
+{
+	struct thread_info *tinfo_send = (struct thread_info *)arg;
+
+	fpga_chnl_io io_send;
+
+	io_send.id = tinfo_send->fpga->id;
+	io_send.chnl = tinfo_send->chnl;
+	io_send.len = tinfo_send->len;
+	io_send.offset = tinfo_send->offset;
+	io_send.last = tinfo_send->last;
+	io_send.timeout = tinfo_send->timeout;
+	io_send.data = (char *)(tinfo_send->buffer);
+
+	int number_of_words_sent =
+		ioctl(tinfo_send->fpga->fd, IOCTL_SEND, &io_send);
+
+	pthread_exit((void *)(intptr_t)number_of_words_sent);
+}
+
+//int fpga_recv(fpga_t * fpga, int chnl, void * data, int len, long long timeout)
+void *fpga_recv(void *arg)
+{
+	struct thread_info *tinfo_recv = (struct thread_info *)arg;
+
+	fpga_chnl_io io_recv;
+
+	io_recv.id = tinfo_recv->fpga->id;
+	io_recv.chnl = tinfo_recv->chnl;
+	io_recv.len = tinfo_recv->len;
+	io_recv.timeout = tinfo_recv->timeout;
+	io_recv.data = (char *)(tinfo_recv->buffer);
+
+	int number_of_words_recv =
+		ioctl(tinfo_recv->fpga->fd, IOCTL_RECV, &io_recv);
+
+	pthread_exit((void *)(intptr_t)number_of_words_recv);
+}
+
+void fpga_reset(fpga_t *fpga)
+{
+	ioctl(fpga->fd, IOCTL_RESET, fpga->id);
+}
+
+int fpga_list(fpga_info_list *list)
+{
+	int fd;
+	int rc;
+
+	fd = open("/dev/" DEVICE_NAME, O_RDWR | O_SYNC);
+	if (fd < 0)
+		return fd;
+	rc = ioctl(fd, IOCTL_LIST, list);
+	close(fd);
+	return rc;
+}
diff --git a/drivers/staging/riffa/riffa.h b/drivers/staging/riffa/riffa.h
new file mode 100644
index 000000000000..0e103b790dda
--- /dev/null
+++ b/drivers/staging/riffa/riffa.h
@@ -0,0 +1,121 @@
+// ----------------------------------------------------------------------
+// Copyright (c) 2016, The Regents of the University of California All
+// rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//
+//     * Neither the name of The Regents of the University of California
+//       nor the names of its contributors may be used to endorse or
+//       promote products derived from this software without specific
+//       prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL REGENTS OF THE
+// UNIVERSITY OF CALIFORNIA BE LIABLE FOR ANY DIRECT, INDIRECT,
+// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+// OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+// TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+// USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+// DAMAGE.
+// ----------------------------------------------------------------------
+
+/*
+ * Filename: riffa.h
+ * Version: 2.0
+ * Description: Linux PCIe communications API for RIFFA.
+ * Author: Matthew Jacobsen
+ * History: @mattj: Initial release. Version 2.0.
+ */
+
+#ifndef RIFFA_H
+#define RIFFA_H
+
+#include "riffa_driver.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct fpga_t;
+typedef struct fpga_t fpga_t;
+
+/**
+ * Populates the fpga_info_list pointer with all FPGAs registered in the system.
+ * Returns 0 on success, a negative value on error.
+ */
+int fpga_list(fpga_info_list *list);
+
+/**
+ * Initializes the FPGA specified by id. On success, returns a pointer to a 
+ * fpga_t struct. On error, returns NULL. Each FPGA must be opened before any 
+ * channels can be accessed. Once opened, any number of threads can use the 
+ * fpga_t struct.
+ */
+fpga_t *fpga_open(int id);
+
+/**
+ * Cleans up memory/resources for the FPGA specified by the fd descriptor.
+ */
+void fpga_close(fpga_t *fpga);
+
+/**
+ * Sends len words (4 byte words) from data to FPGA channel chnl using the 
+ * fpga_t struct. The FPGA channel will be sent len, destoff, and last. If last
+ * is 1, the channel should interpret the end of this send as the end of a
+ * transaction. If last is 0, the channel should wait for additional sends 
+ * before the end of the transaction. If timeout is non-zero, this call will 
+ * send data and wait up to timeout ms for the FPGA to respond (between
+ * packets) before timing out. If timeout is zero, this call may block 
+ * indefinitely. Multiple threads sending on the same channel may result in 
+ * corrupt data or error. This function is thread safe across channels.
+ * On success, returns the number of words sent. On error returns a negative 
+ * value. 
+ */
+//int fpga_send(fpga_t * fpga, int chnl, void * data, int len, int destoff, int last, long long timeout);
+void *fpga_send(void *arg);
+
+/**
+ * Receives data from the FPGA channel chnl to the data pointer, using the 
+ * fpga_t struct. The FPGA channel can send any amount of data, so the data 
+ * array should be large enough to accommodate. The len parameter specifies the
+ * actual size of the data buffer in words (4 byte words). The FPGA channel will
+ * specify an offset which will determine where in the data array the data will
+ * start being written. If the amount of data (plus offset) exceed the size of
+ * the data array (len), then that data will be discarded. If timeout is 
+ * non-zero, this call will wait up to timeout ms for the FPGA to respond 
+ * (between packets) before timing out. If timeout is zero, this call may block 
+ * indefinitely. Multiple threads receiving on the same channel may result in 
+ * corrupt data or error. This function is thread safe across channels.
+ * On success, returns the number of words written to the data array. On error 
+ * returns a negative value. 
+ */
+//int fpga_recv(fpga_t * fpga, int chnl, void * data, int len, long long timeout);
+void *fpga_recv(void *arg);
+
+/**
+ * Resets the state of the FPGA and all transfers across all channels. This is
+ * meant to be used as an alternative to rebooting if an error occurs while 
+ * sending/receiving. Calling this function while other threads are sending or
+ * receiving will result in unexpected behavior.
+ */
+void fpga_reset(fpga_t *fpga);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/drivers/staging/riffa/riffa_driver.c b/drivers/staging/riffa/riffa_driver.c
new file mode 100644
index 000000000000..57f8683dcc36
--- /dev/null
+++ b/drivers/staging/riffa/riffa_driver.c
@@ -0,0 +1,1881 @@
+// ----------------------------------------------------------------------
+// Copyright (c) 2016, The Regents of the University of California All
+// rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//
+//     * Neither the name of The Regents of the University of California
+//       nor the names of its contributors may be used to endorse or
+//       promote products derived from this software without specific
+//       prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL REGENTS OF THE
+// UNIVERSITY OF CALIFORNIA BE LIABLE FOR ANY DIRECT, INDIRECT,
+// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+// OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+// TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+// USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+// DAMAGE.
+// ----------------------------------------------------------------------
+
+/*
+ * Filename: riffa_driver.c
+ * Version: 2.0
+ * Description: Linux PCIe device driver for RIFFA. Uses Linux kernel APIs in
+ *  version 2.6.27+ (tested on version 2.6.32 - 3.3.0).
+ * Author: Matthew Jacobsen
+ * History: @mattj: Initial release. Version 2.0.
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/version.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/fs.h>
+#include <linux/pci.h>
+#include <linux/interrupt.h>
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 11, 0)
+#include <linux/sched.h>
+#else
+#include <linux/sched/signal.h>
+#endif
+
+#include <linux/rwsem.h>
+#include <linux/dma-mapping.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <asm/uaccess.h>
+#include <asm/div64.h>
+#include "riffa_driver.h"
+#include "circ_queue.h"
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_DESCRIPTION("PCIe driver for RIFFA, Linux (2.6.27+)");
+MODULE_AUTHOR("Matt Jacobsen, Patrick Lai");
+
+#ifndef __devinit
+#define __devinit
+#define __devexit
+#define __devexit_p
+#endif
+
+#define CHNL_REG(c, o) ((c << 4) + o)
+#if !defined(__LP64__) && !defined(_LP64)
+#define BUILD_32 1
+#endif
+
+#define CHNL_FLAG_BUSY 0
+
+struct sg_mapping {
+	struct page **pages;
+	struct scatterlist *sgl;
+	enum dma_data_direction direction;
+	int num_sg;
+	unsigned long num_pages;
+	unsigned long long length;
+	unsigned long long overflow;
+};
+
+struct chnl_dir {
+	volatile unsigned long flags;
+	wait_queue_head_t waitq;
+	struct circ_queue *msgs;
+	void *buf_addr;
+	dma_addr_t buf_hw_addr;
+	struct sg_mapping *sg_map_0;
+	struct sg_mapping *sg_map_1;
+};
+
+struct fpga_state {
+	struct pci_dev *dev;
+	unsigned long long irq;
+	void __iomem *bar0;
+	unsigned long long bar0_addr;
+	unsigned long long bar0_len;
+	unsigned long long bar0_flags;
+	atomic_t intr_disabled;
+	void *spill_buf_addr;
+	dma_addr_t spill_buf_hw_addr;
+	int num_sg;
+	int sg_buf_size;
+	int id;
+	char name[16];
+	int vendor_id;
+	int device_id;
+	int num_chnls;
+	struct chnl_dir **recv;
+	struct chnl_dir **send;
+};
+
+// Global variables (to this file only)
+static struct class *mymodule_class;
+static dev_t devt;
+static atomic_t used_fpgas[NUM_FPGAS];
+static struct fpga_state *fpgas[NUM_FPGAS];
+
+static unsigned int tx_len;
+static bool recv_sg_buf_populated;
+
+///////////////////////////////////////////////////////
+// MEMORY ALLOCATION & HELPER FUNCTIONS
+///////////////////////////////////////////////////////
+
+/** 
+ * Returns the value at the specified address.
+ */
+static inline unsigned int read_reg(struct fpga_state *sc, int offset)
+{
+	return readl(sc->bar0 + (offset << 2));
+}
+
+/** 
+ * Writes the value to the specified address.
+ */
+static inline void write_reg(struct fpga_state *sc, int offset,
+			     unsigned int val)
+{
+	writel(val, sc->bar0 + (offset << 2));
+}
+
+#ifdef BUILD_32
+/**
+ * Needed for 32 bit OS because dma_map_sg macro eventually does some 64 bit
+ * division.
+ */
+unsigned long long __udivdi3(unsigned long long num, unsigned long long den)
+{
+	do_div(num, den);
+	return num;
+}
+#endif
+
+// These are not defined in the 2.x.y kernels, so just define them
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2, 6, 39)
+#define PCI_EXP_DEVCTL2_IDO_REQ_EN 0x100
+#define PCI_EXP_DEVCTL2_IDO_CMP_EN 0x200
+#else
+/** 
+ * These are badly named in pre-3.6.11 kernel versions.  We COULD do the same
+ * check as above, however (annoyingly) linux for tegra (based on post-3.6.11)
+ * picked up the header file from some pre-3.6.11 version, so we'll just make
+ * our code ugly and handle the check here:
+ */
+#ifndef PCI_EXP_DEVCTL2_IDO_REQ_EN
+#define PCI_EXP_DEVCTL2_IDO_REQ_EN PCI_EXP_IDO_REQ_EN
+#endif
+#ifndef PCI_EXP_DEVCTL2_IDO_CMP_EN
+#define PCI_EXP_DEVCTL2_IDO_CMP_EN PCI_EXP_IDO_CMP_EN
+#endif
+#endif
+
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(3, 6, 11)
+/**
+ * Code used to set ETB and RCB, but not available before 3.0, or incorrectly
+ * defined before 3.7. As it is peppered throughout the clean up code, it's just
+ * easier to copy the declarations (not verbatim) here than a bunch of conditionals
+ * everywhere else.
+ */
+
+int pcie_capability_read_word(struct pci_dev *dev, int pos, u16 *val)
+{
+	int ret;
+
+	*val = 0;
+	if (pos & 1)
+		return -EINVAL;
+
+	ret = pci_read_config_word(dev, pci_pcie_cap(dev) + pos, val);
+	/*
+	 * Reset *val to 0 if pci_read_config_word() fails, it may
+	 * have been written as 0xFFFF if hardware error happens
+	 * during pci_read_config_word().
+	 */
+	if (ret)
+		*val = 0;
+	return ret;
+}
+
+int pcie_capability_read_dword(struct pci_dev *dev, int pos, u32 *val)
+{
+	int ret;
+
+	*val = 0;
+	if (pos & 3)
+		return -EINVAL;
+
+	ret = pci_read_config_dword(dev, pci_pcie_cap(dev) + pos, val);
+	/*
+	 * Reset *val to 0 if pci_read_config_dword() fails, it may
+	 * have been written as 0xFFFFFFFF if hardware error happens
+	 * during pci_read_config_dword().
+	 */
+	if (ret)
+		*val = 0;
+	return ret;
+}
+
+int pcie_capability_write_word(struct pci_dev *dev, int pos, u16 val)
+{
+	if (pos & 1)
+		return -EINVAL;
+
+	return pci_write_config_word(dev, pci_pcie_cap(dev) + pos, val);
+}
+
+int pcie_capability_write_dword(struct pci_dev *dev, int pos, u32 val)
+{
+	if (pos & 3)
+		return -EINVAL;
+
+	return pci_write_config_dword(dev, pci_pcie_cap(dev) + pos, val);
+}
+#endif
+
+///////////////////////////////////////////////////////
+// INTERRUPT HANDLER
+///////////////////////////////////////////////////////
+
+/**
+ * Reads the interrupt vector and processes it. If processing VECT0, off will
+ * be 0. If processing VECT1, off will be 6.
+ */
+static inline void process_intr_vector(struct fpga_state *sc, int off,
+				       unsigned int vect)
+{
+	// VECT_0/VECT_1 are organized from right to left (LSB to MSB) as:
+	// [ 0] TX_TXN			for channel 0 in VECT_0, channel 6 in VECT_1
+	// [ 1] TX_SG_BUF_RECVD	for channel 0 in VECT_0, channel 6 in VECT_1
+	// [ 2] TX_TXN_DONE		for channel 0 in VECT_0, channel 6 in VECT_1
+	// [ 3] RX_SG_BUF_RECVD	for channel 0 in VECT_0, channel 6 in VECT_1
+	// [ 4] RX_TXN_DONE		for channel 0 in VECT_0, channel 6 in VECT_1
+	// ...
+	// [25] TX_TXN			for channel 5 in VECT_0, channel 11 in VECT_1
+	// [26] TX_SG_BUF_RECVD	for channel 5 in VECT_0, channel 11 in VECT_1
+	// [27] TX_TXN_DONE		for channel 5 in VECT_0, channel 11 in VECT_1
+	// [28] RX_SG_BUF_RECVD	for channel 5 in VECT_0, channel 11 in VECT_1
+	// [29] RX_TXN_DONE		for channel 5 in VECT_0, channel 11 in VECT_1
+	// Positions 30 - 31 in both VECT_0 and VECT_1 are zero.
+
+	unsigned int offlast;
+	unsigned int len;
+	int recv;
+	int send;
+	int chnl;
+	int i;
+
+	//printk(KERN_INFO "riffa: intrpt_handler received:%08x\n", vect);
+	if (vect & 0xC0000000) {
+		printk(KERN_ERR
+		       "riffa: fpga:%d, received bad interrupt vector:%08x\n",
+		       sc->id, vect);
+		return;
+	}
+
+	for (i = 0; i < 6 && (i + off) < sc->num_chnls; ++i) {
+		chnl = i + off;
+		recv = 0;
+		send = 0;
+
+		// TX (PC receive) scatter gather buffer is read.
+		if (vect & (1 << ((5 * i) + 1))) {
+			recv = 1;
+			// Keep track so the thread can handle this.
+			if (push_circ_queue(sc->recv[chnl]->msgs,
+					    EVENT_SG_BUF_READ, 0)) {
+				printk(KERN_ERR
+				       "riffa: fpga:%d chnl:%d, recv sg buf read msg queue full\n",
+				       sc->id, chnl);
+			}
+			DEBUG_MSG(KERN_INFO
+				  "riffa: fpga:%d chnl:%d, recv sg buf read\n",
+				  sc->id, chnl);
+		}
+
+		// TX (PC receive) transaction done.
+		if (vect & (1 << ((5 * i) + 2))) {
+			recv = 1;
+			// Read the transferred amount.
+			len = read_reg(sc, CHNL_REG(chnl, TX_TNFR_LEN_REG_OFF));
+			// Notify the thread.
+			if (push_circ_queue(sc->recv[chnl]->msgs,
+					    EVENT_TXN_DONE, len)) {
+				printk(KERN_ERR
+				       "riffa: fpga:%d chnl:%d, recv txn done msg queue full\n",
+				       sc->id, chnl);
+			}
+			DEBUG_MSG(KERN_INFO
+				  "riffa: fpga:%d chnl:%d, recv txn done\n",
+				  sc->id, chnl);
+		}
+
+		// New TX (PC receive) transaction.
+		if (vect & (1 << ((5 * i) + 0))) {
+			recv = 1;
+			recv_sg_buf_populated = 0; // resets for new transaction
+
+			// Read the offset/last and length
+			offlast = read_reg(sc,
+					   CHNL_REG(chnl, TX_OFFLAST_REG_OFF));
+			tx_len = read_reg(sc, CHNL_REG(chnl, TX_LEN_REG_OFF));
+			// Keep track of this transaction
+			if (push_circ_queue(sc->recv[chnl]->msgs,
+					    EVENT_TXN_OFFLAST, offlast)) {
+				printk(KERN_ERR
+				       "riffa: fpga:%d chnl:%d, recv txn offlast msg queue full\n",
+				       sc->id, chnl);
+			}
+			/*if (push_circ_queue(sc->recv[chnl]->msgs, EVENT_TXN_LEN, len)) {
+				printk(KERN_ERR "riffa: fpga:%d chnl:%d, recv txn len msg queue full\n", sc->id, chnl);
+			}*/
+			DEBUG_MSG(
+				KERN_INFO
+				"riffa: fpga:%d chnl:%d, recv txn (len:%d off:%d last:%d)\n",
+				sc->id, chnl, tx_len, (offlast >> 1),
+				(offlast & 0x1));
+		}
+
+		// RX (PC send) scatter gather buffer is read.
+		if (vect & (1 << ((5 * i) + 3))) {
+			send = 1;
+			// Keep track so the thread can handle this.
+			if (push_circ_queue(sc->send[chnl]->msgs,
+					    EVENT_SG_BUF_READ, 0)) {
+				printk(KERN_ERR
+				       "riffa: fpga:%d chnl:%d, send sg buf read msg queue full\n",
+				       sc->id, chnl);
+			}
+			DEBUG_MSG(KERN_INFO
+				  "riffa: fpga:%d chnl:%d, send sg buf read\n",
+				  sc->id, chnl);
+		}
+
+		// RX (PC send) transaction done.
+		if (vect & (1 << ((5 * i) + 4))) {
+			send = 1;
+			// Read the transferred amount.
+			len = read_reg(sc, CHNL_REG(chnl, RX_TNFR_LEN_REG_OFF));
+			// Notify the thread.
+			if (push_circ_queue(sc->send[chnl]->msgs,
+					    EVENT_TXN_DONE, len)) {
+				printk(KERN_ERR
+				       "riffa: fpga:%d chnl:%d, send txn done msg queue full\n",
+				       sc->id, chnl);
+			}
+			DEBUG_MSG(KERN_INFO
+				  "riffa: fpga:%d chnl:%d, send txn done\n",
+				  sc->id, chnl);
+		}
+
+		// Wake up the thread?
+		if (recv)
+			wake_up(&sc->recv[chnl]->waitq);
+		if (send)
+			wake_up(&sc->send[chnl]->waitq);
+	}
+}
+
+/**
+ * Interrupt handler for all interrupts on all files. Reads data/values
+ * from FPGA and wakes up waiting threads to process the data. Always returns
+ * IRQ_HANDLED.
+ */
+static irqreturn_t intrpt_handler(int irq, void *dev_id)
+{
+	unsigned int vect0;
+	unsigned int vect1;
+	struct fpga_state *sc;
+
+	sc = (struct fpga_state *)dev_id;
+	vect0 = 0;
+	vect1 = 0;
+
+	if (sc == NULL) {
+		printk(KERN_ERR "riffa: invalid fpga_state pointer\n");
+		return IRQ_HANDLED;
+	}
+
+	if (!atomic_read(&sc->intr_disabled)) {
+		// Read the interrupt vector(s):
+		vect0 = read_reg(sc, IRQ_REG0_OFF);
+		if (sc->num_chnls > 6)
+			vect1 = read_reg(sc, IRQ_REG1_OFF);
+
+		// Process the vector(s)
+		process_intr_vector(sc, 0, vect0);
+		if (sc->num_chnls > 6)
+			process_intr_vector(sc, 6, vect1);
+	}
+
+	return IRQ_HANDLED;
+}
+
+///////////////////////////////////////////////////////
+// FILE OPERATION HANDLERS
+///////////////////////////////////////////////////////
+
+/**
+ * Creates and returns a struct_sg_mapping that holds all the data for the user
+ * pages that have been mapped into a scatterlist array. Assumes the user data
+ * is 32 bit word aligned. Up to length bytes from the udata pointer will be
+ * mapped. After all length bytes are mapped, up to overflow bytes will be
+ * mapped using the common spill buffer for the channel. The overflow is used
+ * if we run out of space in the supplied udata pointer.
+ */
+static inline struct sg_mapping *fill_sg_buf(struct fpga_state *sc, int chnl,
+					     void *sg_buf, unsigned long udata,
+					     unsigned long long length,
+					     unsigned long long overflow,
+					     enum dma_data_direction direction)
+{
+	const char *dir = (direction == DMA_TO_DEVICE ? "send" : "recv");
+	struct sg_mapping *sg_map;
+	struct page **pages = NULL;
+	struct scatterlist *sgl = NULL;
+	struct scatterlist *sg;
+	unsigned long num_pages_reqd = 0;
+	long num_pages = 0;
+	unsigned int fp_offset;
+	unsigned int len;
+	unsigned int hw_len;
+	dma_addr_t hw_addr;
+	unsigned long long len_rem = length;
+	unsigned long long overflow_rem = overflow;
+	unsigned int *sg_buf_ptr = (unsigned int *)sg_buf;
+	int num_sg = 0;
+	int i;
+
+	// Create the sg_mapping struct.
+	if ((sg_map = (struct sg_mapping *)kmalloc(sizeof(*sg_map),
+						   GFP_KERNEL)) == NULL) {
+		printk(KERN_ERR
+		       "riffa: fpga:%d chnl:%d, %s could not allocate memory for sg_mapping struct\n",
+		       sc->id, chnl, dir);
+		return NULL;
+	}
+
+	if (length > 0) {
+		// Create the pages array.
+		num_pages_reqd = ((udata + length - 1) >> PAGE_SHIFT) -
+				 (udata >> PAGE_SHIFT) + 1;
+		num_pages_reqd = (num_pages_reqd > sc->num_sg ? sc->num_sg :
+								num_pages_reqd);
+		if ((pages = kmalloc(num_pages_reqd * sizeof(*pages),
+				     GFP_KERNEL)) == NULL) {
+			printk(KERN_ERR
+			       "riffa: fpga:%d chnl:%d, %s could not allocate memory for pages array\n",
+			       sc->id, chnl, dir);
+			kfree(sg_map);
+			return NULL;
+		}
+
+		// Page in the user pages.
+		down_read(&current->mm->mmap_sem);
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 6, 0)
+		num_pages = get_user_pages(current, current->mm, udata,
+					   num_pages_reqd, 1, 0, pages, NULL);
+#elsif LINUX_VERSION_CODE < KERNEL_VERSION(4, 9, 0)
+		num_pages = get_user_pages(udata, num_pages_reqd, 1, 0, pages,
+					   NULL);
+#else
+		num_pages = get_user_pages(udata, num_pages_reqd, FOLL_WRITE,
+					   pages, NULL);
+#endif
+		up_read(&current->mm->mmap_sem);
+		if (num_pages <= 0) {
+			printk(KERN_ERR
+			       "riffa: fpga:%d chnl:%d, %s unable to pin any pages in memory\n",
+			       sc->id, chnl, dir);
+			kfree(pages);
+			kfree(sg_map);
+			return NULL;
+		}
+
+		// Create the scatterlist array.
+		if ((sgl = kcalloc(num_pages, sizeof(*sgl), GFP_KERNEL)) ==
+		    NULL) {
+			printk(KERN_ERR
+			       "riffa: fpga:%d chnl:%d, %s could not allocate memory for scatterlist array\n",
+			       sc->id, chnl, dir);
+			for (i = 0; i < num_pages; ++i)
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 6, 0)
+				page_cache_release(pages[i]);
+#else
+				put_page(pages[i]);
+#endif
+			kfree(pages);
+			kfree(sg_map);
+			return NULL;
+		}
+
+		// Set the scatterlist values
+		fp_offset = (udata & (~PAGE_MASK));
+		sg_init_table(sgl, num_pages);
+		for (i = 0; i < num_pages; ++i) {
+			len = ((fp_offset + len_rem) > PAGE_SIZE ?
+				       (PAGE_SIZE - fp_offset) :
+				       len_rem);
+			sg_set_page(&sgl[i], pages[i], len, fp_offset);
+			len_rem -= len;
+			fp_offset = 0;
+		}
+
+		// Map the scatterlist values and write to the common buffer area
+		num_sg = dma_map_sg(&sc->dev->dev, sgl, num_pages, direction);
+		for_each_sg (sgl, sg, num_sg, i) {
+			hw_addr = sg_dma_address(sg);
+			hw_len = sg_dma_len(sg);
+			sg_buf_ptr[(i * 4) + 0] = (hw_addr & 0xFFFFFFFF);
+			sg_buf_ptr[(i * 4) + 1] =
+				((hw_addr >> 32) & 0xFFFFFFFF);
+			sg_buf_ptr[(i * 4) + 2] = hw_len >> 2; // Words!
+		}
+	}
+
+	// Provide scatter gather mappings for overflow data (all in spill common buffer)
+	while (len_rem == 0 && overflow_rem > 0 && num_sg < sc->num_sg) {
+		sg_buf_ptr[(num_sg * 4) + 0] =
+			(sc->spill_buf_hw_addr & 0xFFFFFFFF);
+		sg_buf_ptr[(num_sg * 4) + 1] =
+			((sc->spill_buf_hw_addr >> 32) & 0xFFFFFFFF);
+		sg_buf_ptr[(num_sg * 4) + 2] = SPILL_BUF_SIZE >> 2; // Words!
+		num_sg++;
+		overflow_rem -=
+			(SPILL_BUF_SIZE > overflow ? overflow : SPILL_BUF_SIZE);
+	}
+
+	// Populate the number of bytes mapped and other sg data
+	sg_map->direction = direction;
+	sg_map->num_pages = num_pages;
+	sg_map->num_sg = num_sg;
+	sg_map->length = (length - len_rem);
+	sg_map->overflow = (overflow - overflow_rem);
+	sg_map->pages = pages;
+	sg_map->sgl = sgl;
+
+	return sg_map;
+}
+
+/**
+ * Frees the scatterlist mappings in the struct sg_mapping pointer and frees all
+ * corresponding structs.
+ */
+static inline void free_sg_buf(struct fpga_state *sc, struct sg_mapping *sg_map)
+{
+	int i;
+
+	if (sg_map == NULL)
+		return;
+
+	// Unmap the pages.
+	if (sg_map->sgl != NULL)
+		dma_unmap_sg(&sc->dev->dev, sg_map->sgl, sg_map->num_pages,
+			     sg_map->direction);
+
+	// Free the pages (mark dirty if necessary).
+	if (sg_map->pages != NULL) {
+		if (sg_map->direction == DMA_FROM_DEVICE) {
+			for (i = 0; i < sg_map->num_pages; ++i) {
+				if (!PageReserved(sg_map->pages[i]))
+					SetPageDirty(sg_map->pages[i]);
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 6, 0)
+				page_cache_release(sg_map->pages[i]);
+#else
+				put_page(sg_map->pages[i]);
+#endif
+			}
+		} else {
+			for (i = 0; i < sg_map->num_pages; ++i) {
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 6, 0)
+				page_cache_release(sg_map->pages[i]);
+#else
+				put_page(sg_map->pages[i]);
+#endif
+			}
+		}
+	}
+
+	// Free the structures.
+	if (sg_map->pages != NULL)
+		kfree(sg_map->pages);
+	if (sg_map->sgl != NULL)
+		kfree(sg_map->sgl);
+	kfree(sg_map);
+}
+
+/**
+ * Reads data from the FPGA. Will block until all the data is received from the
+ * FPGA unless timeout is non-zero. If timeout is non-zero, the function will 
+ * block until all the data is received or until the timeout expires. Received 
+ * data will be written directly into the user buffer, bufp, by the DMA process
+ * (using scatter gather). Up to len words (each word == 32 bits) will be 
+ * written. On success, the number of words received are returned. On error, 
+ * returns a negative value. 
+ */
+static inline unsigned int chnl_recv(struct fpga_state *sc, int chnl,
+				     char __user *bufp, unsigned int len,
+				     unsigned long long timeout)
+{
+	struct sg_mapping *sg_map;
+	long tymeouto;
+	long tymeout;
+	int nomsg;
+	unsigned int msg_type;
+	unsigned int msg;
+	int last = -1;
+	unsigned long long offset = 0;
+	unsigned long long length = 0;
+	unsigned long long overflow = 0;
+	unsigned long long capacity = (((unsigned long long)len) << 2);
+	unsigned long long recvd = 0;
+	unsigned long udata = (unsigned long)bufp;
+	unsigned long max_ptr;
+
+	DEFINE_WAIT(wait);
+
+	// Convert timeout to jiffies.
+	tymeout = (timeout == 0 ? MAX_SCHEDULE_TIMEOUT :
+				  (timeout * HZ / 1000 > LONG_MAX ?
+					   LONG_MAX :
+					   timeout * HZ / 1000));
+	tymeouto = tymeout;
+
+	// Initialize the sg_maps
+	sc->recv[chnl]->sg_map_0 = NULL;
+	sc->recv[chnl]->sg_map_1 = NULL;
+
+	// Continue until we get a message or timeout.
+	while (1) {
+		while ((nomsg = pop_circ_queue(sc->recv[chnl]->msgs, &msg_type,
+					       &msg))) {
+			prepare_to_wait(&sc->recv[chnl]->waitq, &wait,
+					TASK_INTERRUPTIBLE);
+			// Another check before we schedule.
+			if ((nomsg = pop_circ_queue(sc->recv[chnl]->msgs,
+						    &msg_type, &msg)))
+				tymeout = schedule_timeout(tymeout);
+			finish_wait(&sc->recv[chnl]->waitq, &wait);
+			if (signal_pending(current)) {
+				free_sg_buf(sc, sc->recv[chnl]->sg_map_0);
+				free_sg_buf(sc, sc->recv[chnl]->sg_map_1);
+				return -ERESTARTSYS;
+			}
+			if (!nomsg)
+				break;
+			if (tymeout == 0) {
+				printk(KERN_ERR
+				       "riffa: fpga:%d chnl:%d, recv timed out\n",
+				       sc->id, chnl);
+				/*free_sg_buf(sc, sc->recv[chnl]->sg_map_0);
+				free_sg_buf(sc, sc->recv[chnl]->sg_map_1);
+				return (unsigned int)(recvd>>2);*/
+			}
+		}
+		tymeout = tymeouto;
+		DEBUG_MSG(KERN_INFO "msg_type: %d\n",
+			  msg_type); // added by cheng fei
+		// Process the message.
+		switch (msg_type) {
+		case EVENT_TXN_OFFLAST:
+			// Read the offset and last flags (always before reading length)
+			offset = (((unsigned long long)(msg >> 1)) << 2);
+			last = (msg & 0x1);
+			//break;
+
+			//case EVENT_TXN_LEN:
+			// Read the length
+			//length = (((unsigned long long)msg)<<2);
+			length = tx_len << 2;
+			recvd = 0;
+			overflow = 0;
+			// Check for address overflow
+			max_ptr = (unsigned long)(udata + offset + length - 1);
+			if (max_ptr < udata) {
+				printk(KERN_ERR
+				       "riffa: fpga:%d chnl:%d, recv pointer address overflow\n",
+				       sc->id, chnl);
+				overflow = length;
+				length = 0;
+			}
+			// Check for capacity overflow
+			if ((offset + length) > capacity) {
+				if (offset > capacity) {
+					overflow = length;
+					length = 0;
+				} else {
+					overflow = length + offset - capacity;
+					length = capacity - offset;
+				}
+			}
+			// Use the recv common buffer to share the scatter gather elements.
+			if (length > 0 || overflow > 0) {
+				udata = udata + offset;
+				sg_map = fill_sg_buf(sc, chnl,
+						     sc->recv[chnl]->buf_addr,
+						     udata, length, overflow,
+						     DMA_FROM_DEVICE);
+				if (sg_map == NULL || sg_map->num_sg == 0)
+					return (unsigned int)(recvd >> 2);
+				// Update based on the sg_mapping
+				udata += sg_map->length;
+				length -= sg_map->length;
+				overflow -= sg_map->overflow;
+				sc->recv[chnl]->sg_map_1 = sg_map;
+				// Let FPGA know about the scatter gather buffer.
+				write_reg(sc,
+					  CHNL_REG(chnl, TX_SG_ADDR_LO_REG_OFF),
+					  (sc->recv[chnl]->buf_hw_addr &
+					   0xFFFFFFFF));
+				write_reg(sc,
+					  CHNL_REG(chnl, TX_SG_ADDR_HI_REG_OFF),
+					  ((sc->recv[chnl]->buf_hw_addr >> 32) &
+					   0xFFFFFFFF));
+				write_reg(sc, CHNL_REG(chnl, TX_SG_LEN_REG_OFF),
+					  4 * sg_map->num_sg);
+
+				recv_sg_buf_populated = 1;
+
+				DEBUG_MSG(
+					KERN_INFO
+					"riffa: fpga:%d chnl:%d, recv sg buf populated, %d sent\n",
+					sc->id, chnl, sg_map->num_sg);
+
+				wake_up(&sc->send[chnl]
+						 ->waitq); // https://elixir.bootlin.com/linux/v4.19-rc7/source/include/linux/wait.h#L476
+				// The @condition is checked each time the waitqueue @wq_head is woken up. wake_up() has to be called after changing any variable that could change the result of the wait condition.
+			}
+			break;
+
+		case EVENT_SG_BUF_READ:
+			// Ignore if we haven't received offlast/len.
+			if (last == -1)
+				break;
+			// Release the previous scatter gather data.
+			if (sc->recv[chnl]->sg_map_0 != NULL)
+				recvd += sc->recv[chnl]->sg_map_0->length;
+			free_sg_buf(sc, sc->recv[chnl]->sg_map_0);
+			sc->recv[chnl]->sg_map_0 = NULL;
+			// Populate the common buffer with more scatter gather data?
+			if (length > 0 || overflow > 0) {
+				sg_map = fill_sg_buf(sc, chnl,
+						     sc->recv[chnl]->buf_addr,
+						     udata, length, overflow,
+						     DMA_FROM_DEVICE);
+				if (sg_map == NULL || sg_map->num_sg == 0) {
+					free_sg_buf(sc,
+						    sc->recv[chnl]->sg_map_0);
+					free_sg_buf(sc,
+						    sc->recv[chnl]->sg_map_1);
+					return (unsigned int)(recvd >> 2);
+				}
+				// Update based on the sg_mapping
+				udata += sg_map->length;
+				length -= sg_map->length;
+				overflow -= sg_map->overflow;
+				sc->recv[chnl]->sg_map_0 =
+					sc->recv[chnl]->sg_map_1;
+				sc->recv[chnl]->sg_map_1 = sg_map;
+				write_reg(sc,
+					  CHNL_REG(chnl, TX_SG_ADDR_LO_REG_OFF),
+					  (sc->recv[chnl]->buf_hw_addr &
+					   0xFFFFFFFF));
+				write_reg(sc,
+					  CHNL_REG(chnl, TX_SG_ADDR_HI_REG_OFF),
+					  ((sc->recv[chnl]->buf_hw_addr >> 32) &
+					   0xFFFFFFFF));
+				write_reg(sc, CHNL_REG(chnl, TX_SG_LEN_REG_OFF),
+					  4 * sg_map->num_sg);
+				DEBUG_MSG(
+					KERN_INFO
+					"riffa: fpga:%d chnl:%d, recv sg buf populated, %d sent\n",
+					sc->id, chnl, sg_map->num_sg);
+			}
+			break;
+
+		case EVENT_TXN_DONE:
+			recv_sg_buf_populated =
+				0; // resets recv sg buf parameters for next transaction.
+
+			// Ignore if we haven't received offlast/len.
+			if (last == -1)
+				break;
+			// Update with the true value of words transferred.
+			recvd = (((unsigned long long)msg) << 2);
+			// Return if this was the last transaction.
+			free_sg_buf(sc, sc->recv[chnl]->sg_map_0);
+			free_sg_buf(sc, sc->recv[chnl]->sg_map_1);
+			sc->recv[chnl]->sg_map_0 = NULL;
+			sc->recv[chnl]->sg_map_1 = NULL;
+			DEBUG_MSG(KERN_INFO
+				  "riffa: fpga:%d chnl:%d, received %d words\n",
+				  sc->id, chnl, (unsigned int)(recvd >> 2));
+			if (last)
+				return (unsigned int)(recvd >> 2);
+			break;
+
+		default:
+			printk(KERN_ERR
+			       "riffa: fpga:%d chnl:%d, received unknown msg: %08x\n",
+			       sc->id, chnl, msg);
+			break;
+		}
+	}
+
+	return 0;
+}
+
+static inline unsigned int chnl_recv_wrapcheck(struct fpga_state *sc, int chnl,
+					       char __user *bufp,
+					       unsigned int len,
+					       unsigned long long timeout)
+{
+	unsigned long udata = (unsigned long)bufp;
+	unsigned int ret;
+
+	// Validate the parameters.
+	if (chnl >= sc->num_chnls || chnl < 0) {
+		printk(KERN_INFO
+		       "riffa: fpga:%d chnl:%d, recv channel invalid!\n",
+		       sc->id, chnl);
+		return 0;
+	}
+	if (udata & 0x3) {
+		printk(KERN_INFO
+		       "riffa: fpga:%d chnl:%d, recv user buffer must be 32 bit word aligned!\n",
+		       sc->id, chnl);
+		return -EINVAL;
+	}
+
+	// Ensure no simultaneous operations from several threads
+	if (test_and_set_bit(CHNL_FLAG_BUSY, &sc->recv[chnl]->flags) != 0) {
+		printk(KERN_ERR
+		       "riffa: fpga:%d chnl:%d, recv conflict between threads!\n",
+		       sc->id, chnl);
+		return -EBUSY;
+	}
+
+	ret = chnl_recv(sc, chnl, bufp, len, timeout);
+
+	// Clear the busy flag
+	clear_bit(CHNL_FLAG_BUSY, &sc->recv[chnl]->flags);
+
+	return ret;
+}
+
+/**
+ * Writes data to the FPGA channel specified. Will block until all the data is 
+ * sent to the FPGA unless a non-zero timeout is configured. If timeout is non-
+ * zero, then the function will block until all data is sent or when the timeout
+ * ms elapses. User data from the bufp pointer will be sent, up to len words
+ * (each word == 32 bits). The channel will be told how much data to expect and 
+ * at what offset. If last == 1, the FPGA channel will recognize this 
+ * transaction as complete after sending. If last == 0, the FPGA channel will 
+ * expect additional transactions. On success, returns the number of words sent. 
+ * On error, returns a negative value. 
+ */
+static inline unsigned int chnl_send(struct fpga_state *sc, int chnl,
+				     const char __user *bufp, unsigned int len,
+				     unsigned int offset, unsigned int last,
+				     unsigned long long timeout)
+{
+	struct sg_mapping *sg_map;
+	long tymeouto;
+	long tymeout;
+	int nomsg;
+	unsigned int msg_type;
+	unsigned int msg;
+	unsigned long long sent = 0;
+	unsigned long long length = (((unsigned long long)len) << 2);
+	unsigned long udata = (unsigned long)bufp;
+
+	DEFINE_WAIT(wait);
+
+	// Convert timeout to jiffies.
+	tymeout = (timeout == 0 ? MAX_SCHEDULE_TIMEOUT :
+				  (timeout * HZ / 1000 > LONG_MAX ?
+					   LONG_MAX :
+					   timeout * HZ / 1000));
+	tymeouto = tymeout;
+
+	// Clear the message queue.
+	while (!pop_circ_queue(sc->send[chnl]->msgs, &msg_type, &msg))
+		;
+
+	// Initialize the sg_maps
+	sc->send[chnl]->sg_map_0 = NULL;
+	sc->send[chnl]->sg_map_1 = NULL;
+
+	// Let FPGA know about transfer.
+	DEBUG_MSG(KERN_INFO
+		  "riffa: fpga:%d chnl:%d, send (len:%d off:%d last:%d)\n",
+		  sc->id, chnl, len, offset, last);
+	write_reg(sc, CHNL_REG(chnl, RX_OFFLAST_REG_OFF),
+		  ((offset << 1) | last));
+	write_reg(sc, CHNL_REG(chnl, RX_LEN_REG_OFF), len);
+	if (len == 0)
+		return 0;
+
+	// Use the send common buffer to share the scatter gather data
+	sg_map = fill_sg_buf(sc, chnl, sc->send[chnl]->buf_addr, udata, length,
+			     0, DMA_TO_DEVICE);
+	if (sg_map == NULL || sg_map->num_sg == 0)
+		return (unsigned int)(sent >> 2);
+
+	// Update based on the sg_mapping
+	udata += sg_map->length;
+	length -= sg_map->length;
+	sc->send[chnl]->sg_map_1 = sg_map;
+
+	if (tx_len >
+	    0) { // FPGA initiates new Tx transaction, so "yield" to software chnl_recv() thread
+
+		// gives time for software chnl_recv() thread to populate recv sg buf parameter
+		wait_event_interruptible_timeout(sc->send[chnl]->waitq,
+						 (recv_sg_buf_populated == 1),
+						 timeout);
+	}
+
+	// Let FPGA know about the scatter gather buffer.
+	write_reg(sc, CHNL_REG(chnl, RX_SG_ADDR_LO_REG_OFF),
+		  (sc->send[chnl]->buf_hw_addr & 0xFFFFFFFF));
+	write_reg(sc, CHNL_REG(chnl, RX_SG_ADDR_HI_REG_OFF),
+		  ((sc->send[chnl]->buf_hw_addr >> 32) & 0xFFFFFFFF));
+	write_reg(sc, CHNL_REG(chnl, RX_SG_LEN_REG_OFF), 4 * sg_map->num_sg);
+	DEBUG_MSG(KERN_INFO
+		  "riffa: fpga:%d chnl:%d, send sg buf populated, %d sent\n",
+		  sc->id, chnl, sg_map->num_sg);
+
+	// Continue until we get a message or timeout.
+	while (1) {
+		while ((nomsg = pop_circ_queue(sc->send[chnl]->msgs, &msg_type,
+					       &msg))) {
+			prepare_to_wait(&sc->send[chnl]->waitq, &wait,
+					TASK_INTERRUPTIBLE);
+			// Another check before we schedule.
+			if ((nomsg = pop_circ_queue(sc->send[chnl]->msgs,
+						    &msg_type, &msg)))
+				tymeout = schedule_timeout(tymeout);
+			finish_wait(&sc->send[chnl]->waitq, &wait);
+			if (signal_pending(current)) {
+				free_sg_buf(sc, sc->send[chnl]->sg_map_0);
+				free_sg_buf(sc, sc->send[chnl]->sg_map_1);
+				return -ERESTARTSYS;
+			}
+			if (!nomsg)
+				break;
+			if (tymeout == 0) {
+				printk(KERN_ERR
+				       "riffa: fpga:%d chnl:%d, send timed out\n",
+				       sc->id, chnl);
+				/*free_sg_buf(sc, sc->send[chnl]->sg_map_0);
+				free_sg_buf(sc, sc->send[chnl]->sg_map_1);
+				return (unsigned int)(sent>>2);*/
+			}
+		}
+		tymeout = tymeouto;
+
+		// Process the message.
+		switch (msg_type) {
+		case EVENT_SG_BUF_READ:
+			// Release the previous scatter gather data?
+			if (sc->send[chnl]->sg_map_0 != NULL)
+				sent += sc->send[chnl]->sg_map_0->length;
+			free_sg_buf(sc, sc->send[chnl]->sg_map_0);
+			sc->send[chnl]->sg_map_0 = NULL;
+			// Populate the common buffer with more scatter gather data?
+			if (length > 0) {
+				sg_map = fill_sg_buf(sc, chnl,
+						     sc->send[chnl]->buf_addr,
+						     udata, length, 0,
+						     DMA_TO_DEVICE);
+				if (sg_map == NULL || sg_map->num_sg == 0) {
+					free_sg_buf(sc,
+						    sc->send[chnl]->sg_map_0);
+					free_sg_buf(sc,
+						    sc->send[chnl]->sg_map_1);
+					return (unsigned int)(sent >> 2);
+				}
+				// Update based on the sg_mapping
+				udata += sg_map->length;
+				length -= sg_map->length;
+				sc->send[chnl]->sg_map_0 =
+					sc->send[chnl]->sg_map_1;
+				sc->send[chnl]->sg_map_1 = sg_map;
+				write_reg(sc,
+					  CHNL_REG(chnl, RX_SG_ADDR_LO_REG_OFF),
+					  (sc->send[chnl]->buf_hw_addr &
+					   0xFFFFFFFF));
+				write_reg(sc,
+					  CHNL_REG(chnl, RX_SG_ADDR_HI_REG_OFF),
+					  ((sc->send[chnl]->buf_hw_addr >> 32) &
+					   0xFFFFFFFF));
+				write_reg(sc, CHNL_REG(chnl, RX_SG_LEN_REG_OFF),
+					  4 * sg_map->num_sg);
+				DEBUG_MSG(
+					KERN_INFO
+					"riffa: fpga:%d chnl:%d, send sg buf populated, %d sent\n",
+					sc->id, chnl, sg_map->num_sg);
+			}
+			break;
+
+		case EVENT_TXN_DONE:
+			// Update with the true value of words transferred.
+			sent = (((unsigned long long)msg) << 2);
+			// Return as this is the end of the transaction.
+			free_sg_buf(sc, sc->send[chnl]->sg_map_0);
+			free_sg_buf(sc, sc->send[chnl]->sg_map_1);
+			DEBUG_MSG(KERN_INFO
+				  "riffa: fpga:%d chnl:%d, sent %d words\n",
+				  sc->id, chnl, (unsigned int)(sent >> 2));
+			return (unsigned int)(sent >> 2);
+			break;
+
+		default:
+			printk(KERN_ERR
+			       "riffa: fpga:%d chnl:%d, received unknown msg: %08x\n",
+			       sc->id, chnl, msg);
+			break;
+		}
+	}
+
+	return 0;
+}
+
+static inline unsigned int
+chnl_send_wrapcheck(struct fpga_state *sc, int chnl, const char __user *bufp,
+		    unsigned int len, unsigned int offset, unsigned int last,
+		    unsigned long long timeout)
+{
+	unsigned long long length = (((unsigned long long)len) << 2);
+	unsigned long udata = (unsigned long)bufp;
+	unsigned long max_ptr;
+	unsigned int ret;
+
+	// Validate the parameters.
+	if (chnl >= sc->num_chnls || chnl < 0) {
+		printk(KERN_INFO
+		       "riffa: fpga:%d chnl:%d, send channel invalid!\n",
+		       sc->id, chnl);
+		return 0;
+	}
+	max_ptr = (unsigned long)(udata + length - 1);
+	if (max_ptr < udata) {
+		printk(KERN_ERR
+		       "riffa: fpga:%d chnl:%d, send pointer address overflow\n",
+		       sc->id, chnl);
+		return -EINVAL;
+	}
+	if (udata & 0x3) {
+		printk(KERN_INFO
+		       "riffa: fpga:%d chnl:%d, send user buffer must be 32 bit word aligned!\n",
+		       sc->id, chnl);
+		return -EINVAL;
+	}
+
+	// Ensure no simultaneous operations from several threads
+	if (test_and_set_bit(CHNL_FLAG_BUSY, &sc->send[chnl]->flags) != 0) {
+		printk(KERN_ERR
+		       "riffa: fpga:%d chnl:%d, send conflict between threads!\n",
+		       sc->id, chnl);
+		return -EBUSY;
+	}
+
+	ret = chnl_send(sc, chnl, bufp, len, offset, last, timeout);
+
+	// Clear the busy flag
+	clear_bit(CHNL_FLAG_BUSY, &sc->send[chnl]->flags);
+
+	return ret;
+}
+
+/**
+ * Populates the fpga_info struct with the current FPGA state information. On 
+ * success, returns 0. On error, returns a negative value. 
+ */
+static inline int list_fpgas(fpga_info_list *list)
+{
+	int i;
+	int num_fpgas = 0;
+	struct fpga_state *sc;
+
+	for (i = 0; i < NUM_FPGAS; ++i) {
+		if (atomic_read(&used_fpgas[i])) {
+			sc = fpgas[i];
+			list->id[num_fpgas] = sc->id;
+			list->num_chnls[num_fpgas] = sc->num_chnls;
+			list->vendor_id[num_fpgas] = sc->vendor_id;
+			list->device_id[num_fpgas] = sc->device_id;
+			memcpy(list->name[num_fpgas], sc->name,
+			       16 * sizeof(char));
+			num_fpgas++;
+		}
+	}
+	// Zero out the rest
+	for (i = num_fpgas; i < NUM_FPGAS; ++i) {
+		list->id[i] = -1;
+		list->num_chnls[i] = 0;
+		list->vendor_id[i] = 0;
+		list->device_id[i] = 0;
+		memset(list->name[i], 0, 16 * sizeof(char));
+	}
+	list->num_fpgas = num_fpgas;
+
+	return 0;
+}
+
+/**
+ * Resets the driver for the specified FPGA. The fpga_state struct for all 
+ * channels will be reset as will the FPGA itself. 
+ */
+static inline void reset(int id)
+{
+	int i;
+	unsigned int dummy0;
+	unsigned int dummy1;
+	struct fpga_state *sc;
+
+	if (atomic_read(&used_fpgas[id])) {
+		sc = fpgas[id];
+		// Disable interrupts
+		atomic_set(&sc->intr_disabled, 1);
+		// Reset the FPGA
+		read_reg(sc, INFO_REG_OFF);
+
+		// Reset all the channels
+		for (i = 0; i < sc->num_chnls; ++i) {
+			while (!pop_circ_queue(sc->send[i]->msgs, &dummy0,
+					       &dummy1))
+				;
+			while (!pop_circ_queue(sc->recv[i]->msgs, &dummy0,
+					       &dummy1))
+				;
+
+			// resets read and write pointers of the circular queue
+			atomic_set(&sc->recv[i]->msgs->writeIndex, 0);
+			atomic_set(&sc->recv[i]->msgs->readIndex, 0);
+			atomic_set(&sc->send[i]->msgs->writeIndex, 0);
+			atomic_set(&sc->send[i]->msgs->readIndex, 0);
+
+			wake_up(&sc->send[i]->waitq);
+			wake_up(&sc->recv[i]->waitq);
+			clear_bit(CHNL_FLAG_BUSY, &sc->send[i]->flags);
+			clear_bit(CHNL_FLAG_BUSY, &sc->recv[i]->flags);
+		}
+		// Enable interrupts
+		atomic_set(&sc->intr_disabled, 0);
+	}
+}
+
+/**
+ * Main entry point for reading and writing on the device. Return value depends 
+ * on ioctlnum and expected behavior. See code for details.
+ */
+static long fpga_ioctl(struct file *filp, unsigned int ioctlnum,
+		       unsigned long ioctlparam)
+{
+	int rc;
+	fpga_chnl_io io;
+	fpga_info_list list;
+
+	switch (ioctlnum) {
+	case IOCTL_SEND:
+		if ((rc = copy_from_user(&io, (void *)ioctlparam,
+					 sizeof(fpga_chnl_io)))) {
+			printk(KERN_ERR
+			       "riffa: cannot read ioctl user parameter.\n");
+			return rc;
+		}
+		if (io.id < 0 || io.id >= NUM_FPGAS ||
+		    !atomic_read(&used_fpgas[io.id]))
+			return 0;
+		return chnl_send_wrapcheck(fpgas[io.id], io.chnl, io.data,
+					   io.len, io.offset, io.last,
+					   io.timeout);
+	case IOCTL_RECV:
+		if ((rc = copy_from_user(&io, (void *)ioctlparam,
+					 sizeof(fpga_chnl_io)))) {
+			printk(KERN_ERR
+			       "riffa: cannot read ioctl user parameter.\n");
+			return rc;
+		}
+		if (io.id < 0 || io.id >= NUM_FPGAS ||
+		    !atomic_read(&used_fpgas[io.id]))
+			return 0;
+		return chnl_recv_wrapcheck(fpgas[io.id], io.chnl, io.data,
+					   io.len, io.timeout);
+	case IOCTL_LIST:
+		list_fpgas(&list);
+		if ((rc = copy_to_user((void *)ioctlparam, &list,
+				       sizeof(fpga_info_list))))
+			printk(KERN_ERR
+			       "riffa: cannot write ioctl user parameter.\n");
+		return rc;
+	case IOCTL_RESET:
+		reset((int)ioctlparam);
+		break;
+	default:
+		return -ENOTTY;
+		break;
+	}
+	return 0;
+}
+
+///////////////////////////////////////////////////////
+// PCI DRIVER HANDLERS
+///////////////////////////////////////////////////////
+
+/**
+ * Allocates and initializes chnl_dir structs for each channel. Returns the 
+ * number of chnl_dir structs allocated.
+ */
+static inline int __devinit allocate_chnls(struct pci_dev *dev,
+					   struct fpga_state *sc)
+{
+	int i;
+	dma_addr_t hw_addr;
+
+	for (i = 0; i < sc->num_chnls; ++i) {
+		// Allocate the recv struct
+		sc->recv[i] = (struct chnl_dir *)kzalloc(
+			sizeof(struct chnl_dir), GFP_KERNEL);
+		if (sc->recv[i] == NULL)
+			return i;
+		sc->recv[i]->flags = 0;
+		init_waitqueue_head(&sc->recv[i]->waitq);
+		if ((sc->recv[i]->msgs = init_circ_queue(5)) == NULL) {
+			kfree(sc->recv[i]);
+			return i;
+		}
+		sc->recv[i]->buf_addr =
+			pci_alloc_consistent(dev, sc->sg_buf_size, &hw_addr);
+		sc->recv[i]->buf_hw_addr = hw_addr;
+		if (sc->recv[i]->buf_addr == NULL) {
+			free_circ_queue(sc->recv[i]->msgs);
+			kfree(sc->recv[i]);
+			return i;
+		}
+
+		// Allocate the send struct
+		sc->send[i] = (struct chnl_dir *)kzalloc(
+			sizeof(struct chnl_dir), GFP_KERNEL);
+		if (sc->send[i] == NULL) {
+			pci_free_consistent(
+				dev, sc->sg_buf_size, sc->recv[i]->buf_addr,
+				(dma_addr_t)sc->recv[i]->buf_hw_addr);
+			free_circ_queue(sc->recv[i]->msgs);
+			kfree(sc->recv[i]);
+			return i;
+		}
+		sc->send[i]->flags = 0;
+		init_waitqueue_head(&sc->send[i]->waitq);
+		if ((sc->send[i]->msgs = init_circ_queue(4)) == NULL) {
+			kfree(sc->send[i]);
+			pci_free_consistent(
+				dev, sc->sg_buf_size, sc->recv[i]->buf_addr,
+				(dma_addr_t)sc->recv[i]->buf_hw_addr);
+			free_circ_queue(sc->recv[i]->msgs);
+			kfree(sc->recv[i]);
+			return i;
+		}
+		sc->send[i]->buf_addr =
+			pci_alloc_consistent(dev, sc->sg_buf_size, &hw_addr);
+		sc->send[i]->buf_hw_addr = hw_addr;
+		if (sc->send[i]->buf_addr == NULL) {
+			free_circ_queue(sc->send[i]->msgs);
+			kfree(sc->send[i]);
+			pci_free_consistent(
+				dev, sc->sg_buf_size, sc->recv[i]->buf_addr,
+				(dma_addr_t)sc->recv[i]->buf_hw_addr);
+			free_circ_queue(sc->recv[i]->msgs);
+			kfree(sc->recv[i]);
+			return i;
+		}
+	}
+
+	return i;
+}
+
+/**
+ * Called by the OS when the device is ready for access. Returns 0 on success,
+ * negative value on failure.
+ */
+static int __devinit fpga_probe(struct pci_dev *dev,
+				const struct pci_device_id *id)
+{
+	int i;
+	int j;
+	int error;
+	struct fpga_state *sc;
+	dma_addr_t hw_addr;
+	unsigned int reg;
+	u32 lnkctl_result = 0;
+	u32 devctl_result = 0;
+	u32 devctl2_result = 0;
+
+	// Setup the PCIe device.
+	error = pci_enable_device(dev);
+	if (error < 0) {
+		printk(KERN_ERR "riffa: pci_enable_device returned %d\n",
+		       error);
+		return (-ENODEV);
+	}
+
+	// Enable bus master
+	pci_set_master(dev);
+
+	// Set the mask size
+	error = pci_set_dma_mask(dev, DMA_BIT_MASK(64));
+	if (!error)
+		error = pci_set_consistent_dma_mask(dev, DMA_BIT_MASK(64));
+	if (error) {
+		printk(KERN_ERR "riffa: cannot set 64 bit DMA mode\n");
+		pci_disable_device(dev);
+		return error;
+	}
+
+	// Allocate device structure.
+	sc = kzalloc(sizeof(*sc), GFP_KERNEL);
+	if (sc == NULL) {
+		printk(KERN_ERR "riffa: not enough memory to allocate sc\n");
+		pci_disable_device(dev);
+		return (-ENOMEM);
+	}
+	atomic_set(&sc->intr_disabled, 0);
+	snprintf(sc->name, sizeof(sc->name), "%s%d", pci_name(dev), 0);
+	sc->vendor_id = dev->vendor;
+	sc->device_id = dev->device;
+	printk(KERN_INFO "riffa: found FPGA with name: %s\n", sc->name);
+	printk(KERN_INFO "riffa: vendor id: 0x%04X\n", sc->vendor_id);
+	printk(KERN_INFO "riffa: device id: 0x%04X\n", sc->device_id);
+
+	// Setup the BAR memory regions
+	error = pci_request_regions(dev, sc->name);
+	if (error < 0) {
+		printk(KERN_ERR
+		       "riffa: pci_request_regions returned error: %d\n",
+		       error);
+		pci_disable_device(dev);
+		kfree(sc);
+		return (-ENODEV);
+	}
+
+	// PCI BAR 0
+	sc->bar0_addr = pci_resource_start(dev, 0);
+	sc->bar0_len = pci_resource_len(dev, 0);
+	sc->bar0_flags = pci_resource_flags(dev, 0);
+	printk(KERN_INFO "riffa: BAR 0 address: %llx\n", sc->bar0_addr);
+	printk(KERN_INFO "riffa: BAR 0 length: %lld bytes\n", sc->bar0_len);
+	if (sc->bar0_len != 1024) {
+		printk(KERN_ERR "riffa: BAR 0 incorrect length\n");
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return (-ENODEV);
+	}
+	sc->bar0 = ioremap(sc->bar0_addr, sc->bar0_len);
+	if (!sc->bar0) {
+		printk(KERN_ERR "riffa: could not ioremap BAR 0\n");
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return (-ENODEV);
+	}
+
+	// Setup MSI interrupts
+	error = pci_enable_msi(dev);
+	if (error != 0) {
+		printk(KERN_ERR "riffa: pci_enable_msi returned error: %d\n",
+		       error);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return error;
+	}
+
+	// Request an interrupt
+	error = request_irq(dev->irq, intrpt_handler, IRQF_SHARED, sc->name,
+			    sc);
+	if (error != 0) {
+		printk(KERN_ERR "riffa: request_irq(%d) returned error: %d\n",
+		       dev->irq, error);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return error;
+	}
+	sc->irq = dev->irq;
+	printk(KERN_INFO "riffa: MSI setup on irq %d\n", dev->irq);
+
+	// Set extended tag bit
+	error = pcie_capability_read_dword(dev, PCI_EXP_DEVCTL, &devctl_result);
+	if (error != 0) {
+		printk(KERN_ERR
+		       "riffa: pcie_capability_read_dword returned error: %d\n",
+		       error);
+		free_irq(dev->irq, sc);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return error;
+	}
+	printk(KERN_INFO "riffa: PCIE_EXP_DEVCTL register: %x\n",
+	       devctl_result);
+
+	error = pcie_capability_write_dword(
+		dev, PCI_EXP_DEVCTL, (devctl_result | PCI_EXP_DEVCTL_EXT_TAG));
+	if (error != 0) {
+		printk(KERN_ERR
+		       "riffa: pcie_capability_write_dword returned error: %d\n",
+		       error);
+		free_irq(dev->irq, sc);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return error;
+	}
+
+	// Set IDO bits
+	error = pcie_capability_read_dword(dev, PCI_EXP_DEVCTL2,
+					   &devctl2_result);
+	if (error != 0) {
+		printk(KERN_ERR
+		       "riffa: pcie_capability_read_dword returned error: %d\n",
+		       error);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL, devctl_result);
+		free_irq(dev->irq, sc);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return error;
+	}
+	printk(KERN_INFO "riffa: PCIE_EXP_DEVCTL2 register: %x\n",
+	       devctl2_result);
+
+	error = pcie_capability_write_dword(dev, PCI_EXP_DEVCTL2,
+					    (devctl2_result |
+					     PCI_EXP_DEVCTL2_IDO_REQ_EN |
+					     PCI_EXP_DEVCTL2_IDO_CMP_EN));
+	if (error != 0) {
+		printk(KERN_ERR
+		       "riffa: pcie_capability_write_dword returned error: %d\n",
+		       error);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL, devctl_result);
+		free_irq(dev->irq, sc);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return error;
+	}
+
+	// Set RCB to 128
+	error = pcie_capability_read_dword(dev, PCI_EXP_LNKCTL, &lnkctl_result);
+	if (error != 0) {
+		printk(KERN_ERR
+		       "riffa: pcie_capability_read_dword returned error: %d\n",
+		       error);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL2,
+					    devctl2_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL, devctl_result);
+		free_irq(dev->irq, sc);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return error;
+	}
+	printk(KERN_INFO "riffa: PCIE_EXP_LNKCTL register: %x\n",
+	       lnkctl_result);
+
+	error = pcie_capability_write_dword(
+		dev, PCI_EXP_LNKCTL, (lnkctl_result | PCI_EXP_LNKCTL_RCB));
+	if (error != 0) {
+		printk(KERN_ERR
+		       "riffa: pcie_capability_write_dword returned error: %d\n",
+		       error);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL2,
+					    devctl2_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL, devctl_result);
+		free_irq(dev->irq, sc);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return error;
+	}
+	// Read device configuration
+	reg = read_reg(sc, INFO_REG_OFF);
+	sc->num_chnls = ((reg >> 0) & 0xF);
+	sc->num_sg = SG_ELEMS * ((reg >> 19) & 0xF);
+	sc->sg_buf_size = SG_BUF_SIZE * ((reg >> 19) & 0xF);
+	printk(KERN_INFO "riffa: number of channels: %d\n", ((reg >> 0) & 0xF));
+	printk(KERN_INFO "riffa: bus interface width: %d\n", ((reg >> 19) & 0xF)
+								     << 5);
+	printk(KERN_INFO "riffa: bus master enabled: %d\n", ((reg >> 4) & 0x1));
+	printk(KERN_INFO "riffa: negotiated link width: %d\n",
+	       ((reg >> 5) & 0x3F));
+	printk(KERN_INFO "riffa: negotiated link rate: %d MTs\n",
+	       ((reg >> 11) & 0x3) * 2500);
+	printk(KERN_INFO "riffa: max downstream payload: %d bytes\n",
+	       128 << ((reg >> 13) & 0x7));
+	printk(KERN_INFO "riffa: max upstream payload: %d bytes\n",
+	       128 << ((reg >> 16) & 0x7));
+
+	if (((reg >> 4) & 0x1) != 1) {
+		printk(KERN_ERR "riffa: bus master not enabled!\n");
+		pcie_capability_write_dword(dev, PCI_EXP_LNKCTL, lnkctl_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL2,
+					    devctl2_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL, devctl_result);
+		free_irq(dev->irq, sc);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return (-ENODEV);
+	}
+
+	if (((reg >> 5) & 0x3F) == 0 || ((reg >> 11) & 0x3) == 0) {
+		printk(KERN_ERR "riffa: bad link parameters!\n");
+		pcie_capability_write_dword(dev, PCI_EXP_LNKCTL, lnkctl_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL2,
+					    devctl2_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL, devctl_result);
+		free_irq(dev->irq, sc);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return (-ENODEV);
+	}
+
+	if ((reg & 0xF) == 0 || (reg & 0xF) > MAX_CHNLS) {
+		printk(KERN_ERR "riffa: bad number of channels!\n");
+		pcie_capability_write_dword(dev, PCI_EXP_LNKCTL, lnkctl_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL2,
+					    devctl2_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL, devctl_result);
+		free_irq(dev->irq, sc);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return (-ENODEV);
+	}
+
+	if (((reg >> 19) & 0xF) == 0 ||
+	    ((reg >> 19) & 0xF) > MAX_BUS_WIDTH_PARAM) {
+		printk(KERN_ERR "riffa: bad bus width!\n");
+		pcie_capability_write_dword(dev, PCI_EXP_LNKCTL, lnkctl_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL2,
+					    devctl2_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL, devctl_result);
+		free_irq(dev->irq, sc);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return (-ENODEV);
+	}
+
+	// Create chnl_dir structs.
+	sc->recv = (struct chnl_dir **)kzalloc(
+		sc->num_chnls * sizeof(struct chnl_dir *), GFP_KERNEL);
+	sc->send = (struct chnl_dir **)kzalloc(
+		sc->num_chnls * sizeof(struct chnl_dir *), GFP_KERNEL);
+	if (sc->recv == NULL || sc->send == NULL) {
+		printk(KERN_ERR
+		       "riffa: not enough memory to allocate chnl_dir arrays\n");
+		if (sc->recv != NULL)
+			kfree(sc->recv);
+		if (sc->send != NULL)
+			kfree(sc->send);
+		pcie_capability_write_dword(dev, PCI_EXP_LNKCTL, lnkctl_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL2,
+					    devctl2_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL, devctl_result);
+		free_irq(dev->irq, sc);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return (-ENOMEM);
+	}
+	j = allocate_chnls(dev, sc);
+	if (j < sc->num_chnls) {
+		sc->num_chnls = j;
+		printk(KERN_ERR
+		       "riffa: not enough memory to allocate chnl_dir structs\n");
+		for (i = 0; i < sc->num_chnls; ++i) {
+			pci_free_consistent(
+				dev, sc->sg_buf_size, sc->send[i]->buf_addr,
+				(dma_addr_t)sc->send[i]->buf_hw_addr);
+			pci_free_consistent(
+				dev, sc->sg_buf_size, sc->recv[i]->buf_addr,
+				(dma_addr_t)sc->recv[i]->buf_hw_addr);
+			free_circ_queue(sc->send[i]->msgs);
+			free_circ_queue(sc->recv[i]->msgs);
+			kfree(sc->send[i]);
+			kfree(sc->recv[i]);
+		}
+		kfree(sc->recv);
+		kfree(sc->send);
+		pcie_capability_write_dword(dev, PCI_EXP_LNKCTL, lnkctl_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL2,
+					    devctl2_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL, devctl_result);
+		free_irq(dev->irq, sc);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return (-ENOMEM);
+	}
+
+	// Create spill buffer (for overflow on receive).
+	sc->spill_buf_addr =
+		pci_alloc_consistent(dev, SPILL_BUF_SIZE, &hw_addr);
+	sc->spill_buf_hw_addr = hw_addr;
+	if (sc->spill_buf_addr == NULL) {
+		printk(KERN_ERR
+		       "riffa: not enough memory to allocate spill buffer\n");
+		for (i = 0; i < sc->num_chnls; ++i) {
+			pci_free_consistent(
+				dev, sc->sg_buf_size, sc->send[i]->buf_addr,
+				(dma_addr_t)sc->send[i]->buf_hw_addr);
+			pci_free_consistent(
+				dev, sc->sg_buf_size, sc->recv[i]->buf_addr,
+				(dma_addr_t)sc->recv[i]->buf_hw_addr);
+			free_circ_queue(sc->send[i]->msgs);
+			free_circ_queue(sc->recv[i]->msgs);
+			kfree(sc->send[i]);
+			kfree(sc->recv[i]);
+		}
+		pcie_capability_write_dword(dev, PCI_EXP_LNKCTL, lnkctl_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL2,
+					    devctl2_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL, devctl_result);
+		kfree(sc->recv);
+		kfree(sc->send);
+		free_irq(dev->irq, sc);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+	}
+
+	// Save pointer to structure
+	pci_set_drvdata(dev, sc);
+	sc->dev = dev;
+	sc->id = -1;
+	for (i = 0; i < NUM_FPGAS; i++) {
+		if (!atomic_xchg(&used_fpgas[i], 1)) {
+			sc->id = i;
+			fpgas[i] = sc;
+			break;
+		}
+	}
+	if (sc->id == -1) {
+		printk(KERN_ERR
+		       "riffa: could not save FPGA information, %d is limit.\n",
+		       NUM_FPGAS);
+		for (i = 0; i < sc->num_chnls; ++i) {
+			pci_free_consistent(
+				dev, sc->sg_buf_size, sc->send[i]->buf_addr,
+				(dma_addr_t)sc->send[i]->buf_hw_addr);
+			pci_free_consistent(
+				dev, sc->sg_buf_size, sc->recv[i]->buf_addr,
+				(dma_addr_t)sc->recv[i]->buf_hw_addr);
+			free_circ_queue(sc->send[i]->msgs);
+			free_circ_queue(sc->recv[i]->msgs);
+			kfree(sc->send[i]);
+			kfree(sc->recv[i]);
+		}
+		kfree(sc->recv);
+		kfree(sc->send);
+		pci_free_consistent(dev, SPILL_BUF_SIZE, sc->spill_buf_addr,
+				    (dma_addr_t)sc->spill_buf_hw_addr);
+		pcie_capability_write_dword(dev, PCI_EXP_LNKCTL, lnkctl_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL2,
+					    devctl2_result);
+		pcie_capability_write_dword(dev, PCI_EXP_DEVCTL, devctl_result);
+		free_irq(dev->irq, sc);
+		pci_disable_msi(dev);
+		iounmap(sc->bar0);
+		pci_release_regions(dev);
+		pci_disable_device(dev);
+		kfree(sc);
+		return (-ENOMEM);
+	} else {
+		printk(KERN_INFO "riffa: saved FPGA with id: %d\n", sc->id);
+	}
+
+	return 0;
+}
+
+/**
+ * Called when the device is unloaded.
+ */
+static void __devexit fpga_remove(struct pci_dev *dev)
+{
+	int i;
+	u32 result;
+	struct fpga_state *sc;
+
+	pcie_capability_read_dword(dev, PCI_EXP_DEVCTL, &result);
+	pcie_capability_write_dword(dev, PCI_EXP_DEVCTL,
+				    result & ~(PCI_EXP_DEVCTL_EXT_TAG |
+					       PCI_EXP_DEVCTL_RELAX_EN));
+
+	pcie_capability_read_dword(dev, PCI_EXP_DEVCTL2, &result);
+	pcie_capability_write_dword(dev, PCI_EXP_DEVCTL2,
+				    result & ~(PCI_EXP_DEVCTL2_IDO_REQ_EN |
+					       PCI_EXP_DEVCTL2_IDO_CMP_EN));
+
+	pcie_capability_read_dword(dev, PCI_EXP_DEVCTL, &result);
+	pcie_capability_write_dword(dev, PCI_EXP_LNKCTL,
+				    result & (~PCI_EXP_LNKCTL_RCB));
+
+	if ((sc = (struct fpga_state *)pci_get_drvdata(dev)) != NULL) {
+		// Free structs, memory regions, etc.
+		atomic_set(&used_fpgas[sc->id], 0);
+		for (i = 0; i < sc->num_chnls; ++i) {
+			pci_free_consistent(
+				dev, sc->sg_buf_size, sc->send[i]->buf_addr,
+				(dma_addr_t)sc->send[i]->buf_hw_addr);
+			pci_free_consistent(
+				dev, sc->sg_buf_size, sc->recv[i]->buf_addr,
+				(dma_addr_t)sc->recv[i]->buf_hw_addr);
+			free_circ_queue(sc->send[i]->msgs);
+			free_circ_queue(sc->recv[i]->msgs);
+			kfree(sc->send[i]);
+			kfree(sc->recv[i]);
+		}
+		kfree(sc->recv);
+		kfree(sc->send);
+		pci_free_consistent(dev, SPILL_BUF_SIZE, sc->spill_buf_addr,
+				    (dma_addr_t)sc->spill_buf_hw_addr);
+		free_irq(dev->irq, sc);
+		iounmap(sc->bar0);
+		kfree(sc);
+	}
+	pci_disable_msi(dev);
+	pci_release_regions(dev);
+	pci_disable_device(dev);
+	pci_set_drvdata(dev, NULL);
+}
+
+///////////////////////////////////////////////////////
+// MODULE INIT/EXIT FUNCTIONS
+///////////////////////////////////////////////////////
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 8, 0)
+static DEFINE_PCI_DEVICE_TABLE(fpga_ids) =
+#else
+static const struct pci_device_id fpga_ids[] =
+#endif
+	{
+		{ PCI_DEVICE(VENDOR_ID0, PCI_ANY_ID) },
+		{ PCI_DEVICE(VENDOR_ID1, PCI_ANY_ID) },
+		{ 0 },
+	};
+
+MODULE_DEVICE_TABLE(pci, fpga_ids);
+static struct pci_driver fpga_driver = {
+	.name = DEVICE_NAME,
+	.id_table = fpga_ids,
+	.probe = fpga_probe,
+	.remove = __devexit_p(fpga_remove),
+};
+
+static const struct file_operations fpga_fops = {
+	.owner = THIS_MODULE,
+	.unlocked_ioctl = fpga_ioctl,
+};
+
+/**
+ * Called to initialize the PCI device. 
+ */
+static int __init fpga_init(void)
+{
+	int i;
+	int error;
+
+	for (i = 0; i < NUM_FPGAS; i++)
+		atomic_set(&used_fpgas[i], 0);
+
+	error = pci_register_driver(&fpga_driver);
+	if (error != 0) {
+		printk(KERN_ERR "riffa: pci_module_register returned %d\n",
+		       error);
+		return (error);
+	}
+
+	error = register_chrdev(MAJOR_NUM, DEVICE_NAME, &fpga_fops);
+	if (error < 0) {
+		printk(KERN_ERR "riffa: register_chrdev returned %d\n", error);
+		return (error);
+	}
+
+	mymodule_class = class_create(THIS_MODULE, DEVICE_NAME);
+	if (IS_ERR(mymodule_class)) {
+		error = PTR_ERR(mymodule_class);
+		printk(KERN_ERR "riffa: class_create() returned %d\n", error);
+		return (error);
+	}
+
+	devt = MKDEV(MAJOR_NUM, 0);
+	device_create(mymodule_class, NULL, devt, "%s", DEVICE_NAME);
+
+	return 0;
+}
+
+/**
+ * Called to destroy the PCI device.
+ */
+static void __exit fpga_exit(void)
+{
+	device_destroy(mymodule_class, devt);
+	class_destroy(mymodule_class);
+	pci_unregister_driver(&fpga_driver);
+	unregister_chrdev(MAJOR_NUM, DEVICE_NAME);
+}
+
+module_init(fpga_init);
+module_exit(fpga_exit);
diff --git a/drivers/staging/riffa/riffa_driver.h b/drivers/staging/riffa/riffa_driver.h
new file mode 100644
index 000000000000..b0c2038ce09b
--- /dev/null
+++ b/drivers/staging/riffa/riffa_driver.h
@@ -0,0 +1,125 @@
+// ----------------------------------------------------------------------
+// Copyright (c) 2016, The Regents of the University of California All
+// rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//
+//     * Neither the name of The Regents of the University of California
+//       nor the names of its contributors may be used to endorse or
+//       promote products derived from this software without specific
+//       prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL REGENTS OF THE
+// UNIVERSITY OF CALIFORNIA BE LIABLE FOR ANY DIRECT, INDIRECT,
+// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+// OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+// TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+// USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+// DAMAGE.
+// ----------------------------------------------------------------------
+
+/*
+ * Filename: riffa_driver.h
+ * Version: 2.0
+ * Description: Linux PCIe device driver for RIFFA. Uses Linux kernel APIs in
+ *  version 2.6.27+ (tested on version 2.6.32 - 3.3.0).
+ * Author: Matthew Jacobsen
+ * History: @mattj: Initial release. Version 2.0.
+ */
+
+#ifndef RIFFA_DRIVER_H
+#define RIFFA_DRIVER_H
+
+#include <linux/ioctl.h>
+
+#define DEBUG 1
+
+#ifdef DEBUG
+#define DEBUG_MSG(...) printk(__VA_ARGS__)
+#else
+#define DEBUG_MSG(...)
+#endif
+
+// The major device number. We can't rely on dynamic registration because ioctls
+// need to know it.
+#define MAJOR_NUM 100
+#define DEVICE_NAME "riffa"
+#define VENDOR_ID0 0x10EE
+#define VENDOR_ID1 0x1172
+
+// Message events for readmsgs/writemsgs queues.
+#define EVENT_TXN_LEN 1
+#define EVENT_TXN_OFFLAST 2
+#define EVENT_TXN_DONE 3
+#define EVENT_SG_BUF_READ 4
+
+// Constants and device offsets
+#define NUM_FPGAS 5 // max # of FPGAs to support in a single PC
+#define MAX_CHNLS 12 // max # of channels per FPGA
+#define MAX_BUS_WIDTH_PARAM 4 // max bus width parameter
+#define SG_BUF_SIZE (4 * 1024) // size of shared SG buffer
+#define SG_ELEMS 200 // # of SG elements to transfer at a time
+#define SPILL_BUF_SIZE (4 * 1024) // size of shared spill common buffer
+
+#define RX_SG_LEN_REG_OFF 0x0 // config offset for RX SG buf length
+#define RX_SG_ADDR_LO_REG_OFF 0x1 // config offset for RX SG buf low addr
+#define RX_SG_ADDR_HI_REG_OFF 0x2 // config offset for RX SG buf high addr
+#define RX_LEN_REG_OFF 0x3 // config offset for RX txn length
+#define RX_OFFLAST_REG_OFF 0x4 // config offset for RX txn last/offset
+#define RX_TNFR_LEN_REG_OFF 0xD // config offset for RX transfer length
+#define TX_SG_LEN_REG_OFF 0x5 // config offset for TX SG buf length
+#define TX_SG_ADDR_LO_REG_OFF 0x6 // config offset for TX SG buf low addr
+#define TX_SG_ADDR_HI_REG_OFF 0x7 // config offset for TX SG buf high addr
+#define TX_LEN_REG_OFF 0x8 // config offset for TX txn length
+#define TX_OFFLAST_REG_OFF 0x9 // config offset for TX txn last/offset
+#define TX_TNFR_LEN_REG_OFF 0xE // config offset for TX transfer length
+
+#define INFO_REG_OFF 0xA // config offset for link info
+
+#define IRQ_REG0_OFF 0xB // config offset for interrupt reg 0
+#define IRQ_REG1_OFF 0xC // config offset for interrupt reg 1
+
+// Structs
+struct fpga_chnl_io {
+	int id;
+	int chnl;
+	unsigned int len;
+	unsigned int offset;
+	unsigned int last;
+	unsigned long long timeout;
+	char *data;
+};
+typedef struct fpga_chnl_io fpga_chnl_io;
+
+struct fpga_info_list {
+	int num_fpgas;
+	int id[NUM_FPGAS];
+	int num_chnls[NUM_FPGAS];
+	char name[NUM_FPGAS][16];
+	int vendor_id[NUM_FPGAS];
+	int device_id[NUM_FPGAS];
+};
+typedef struct fpga_info_list fpga_info_list;
+
+// IOCTLs
+#define IOCTL_SEND _IOW(MAJOR_NUM, 1, fpga_chnl_io *)
+#define IOCTL_RECV _IOR(MAJOR_NUM, 2, fpga_chnl_io *)
+#define IOCTL_LIST _IOR(MAJOR_NUM, 3, fpga_info_list *)
+#define IOCTL_RESET _IOW(MAJOR_NUM, 4, int)
+
+#endif
-- 
2.17.1

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