diff --git a/hw/core/Makefile.objs b/hw/core/Makefile.objs
index abb3560..bf95db5 100644
--- a/hw/core/Makefile.objs
+++ b/hw/core/Makefile.objs
@@ -14,4 +14,5 @@ common-obj-$(CONFIG_SOFTMMU) += machine.o
 common-obj-$(CONFIG_SOFTMMU) += null-machine.o
 common-obj-$(CONFIG_SOFTMMU) += loader.o
 common-obj-$(CONFIG_SOFTMMU) += qdev-properties-system.o
+common-obj-$(CONFIG_SOFTMMU) += register.o
 common-obj-$(CONFIG_PLATFORM_BUS) += platform-bus.o
diff --git a/hw/core/register.c b/hw/core/register.c
new file mode 100644
index 0000000..1656f71
--- /dev/null
+++ b/hw/core/register.c
@@ -0,0 +1,148 @@
+/*
+ * Register Definition API
+ *
+ * Copyright (c) 2016 Xilinx Inc.
+ * Copyright (c) 2013 Peter Crosthwaite <peter.crosthwaite@xilinx.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "hw/register.h"
+#include "hw/qdev.h"
+#include "qemu/log.h"
+
+static inline void register_write_val(RegisterInfo *reg, uint64_t val)
+{
+    g_assert(reg->data);
+
+    switch (reg->data_size) {
+    case 1:
+        *(uint8_t *)reg->data = val;
+        break;
+    case 2:
+        *(uint16_t *)reg->data = val;
+        break;
+    case 4:
+        *(uint32_t *)reg->data = val;
+        break;
+    case 8:
+        *(uint64_t *)reg->data = val;
+        break;
+    default:
+        g_assert_not_reached();
+    }
+}
+
+static inline uint64_t register_read_val(RegisterInfo *reg)
+{
+    switch (reg->data_size) {
+    case 1:
+        return *(uint8_t *)reg->data;
+    case 2:
+        return *(uint16_t *)reg->data;
+    case 4:
+        return *(uint32_t *)reg->data;
+    case 8:
+        return *(uint64_t *)reg->data;
+    default:
+        g_assert_not_reached();
+    }
+    return 0; /* unreachable */
+}
+
+void register_write(RegisterInfo *reg, uint64_t val, uint64_t we)
+{
+    uint64_t old_val, new_val, test, no_w_mask;
+    const RegisterAccessInfo *ac;
+
+    assert(reg);
+
+    ac = reg->access;
+
+    if (!ac || !ac->name) {
+        qemu_log_mask(LOG_GUEST_ERROR, "%s: write to undefined device state "
+                      "(written value: %#" PRIx64 ")\n", reg->prefix, val);
+        return;
+    }
+
+    old_val = reg->data ? register_read_val(reg) : ac->reset;
+
+    test = (old_val ^ val) & ac->rsvd;
+    if (test) {
+        qemu_log_mask(LOG_GUEST_ERROR, "%s: change of value in reserved bit"
+                      "fields: %#" PRIx64 ")\n", reg->prefix, test);
+    }
+
+    test = val & ac->unimp;
+    if (test) {
+        qemu_log_mask(LOG_UNIMP,
+                      "%s:%s writing %#" PRIx64 " to unimplemented bits:" \
+                      " %#" PRIx64 "",
+                      reg->prefix, reg->access->name, val, ac->unimp);
+    }
+
+    /* Create the no write mask based on the read only, write to clear and
+     * reserved bit masks.
+     */
+    no_w_mask = ac->ro | ac->w1c | ac->rsvd | ~we;
+    new_val = (val & ~no_w_mask) | (old_val & no_w_mask);
+    new_val &= ~(val & ac->w1c);
+
+    if (ac->pre_write) {
+        new_val = ac->pre_write(reg, new_val);
+    }
+
+    if (reg->debug) {
+        qemu_log("%s:%s: write of value %#" PRIx64 "\n", reg->prefix, ac->name,
+                 new_val);
+    }
+
+    register_write_val(reg, new_val);
+
+    if (ac->post_write) {
+        ac->post_write(reg, new_val);
+    }
+}
+
+uint64_t register_read(RegisterInfo *reg)
+{
+    uint64_t ret;
+    const RegisterAccessInfo *ac;
+
+    assert(reg);
+
+    ac = reg->access;
+    if (!ac || !ac->name) {
+        qemu_log_mask(LOG_GUEST_ERROR, "%s: read from undefined device state\n",
+                      reg->prefix);
+        return 0;
+    }
+
+    ret = reg->data ? register_read_val(reg) : ac->reset;
+
+    register_write_val(reg, ret & ~ac->cor);
+
+    if (ac->post_read) {
+        ret = ac->post_read(reg, ret);
+    }
+
+    if (reg->debug) {
+        qemu_log("%s:%s: read of value %#" PRIx64 "\n", reg->prefix,
+                 ac->name, ret);
+    }
+
+    return ret;
+}
+
+void register_reset(RegisterInfo *reg)
+{
+    g_assert(reg);
+
+    if (!reg->data || !reg->access) {
+        return;
+    }
+
+    register_write_val(reg, reg->access->reset);
+}
diff --git a/include/hw/register.h b/include/hw/register.h
new file mode 100644
index 0000000..baa08f5
--- /dev/null
+++ b/include/hw/register.h
@@ -0,0 +1,108 @@
+/*
+ * Register Definition API
+ *
+ * Copyright (c) 2016 Xilinx Inc.
+ * Copyright (c) 2013 Peter Crosthwaite <peter.crosthwaite@xilinx.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+
+#ifndef REGISTER_H
+#define REGISTER_H
+
+#include "exec/memory.h"
+
+typedef struct RegisterInfo RegisterInfo;
+typedef struct RegisterAccessInfo RegisterAccessInfo;
+
+/**
+ * Access description for a register that is part of guest accessible device
+ * state.
+ *
+ * @name: String name of the register
+ * @ro: whether or not the bit is read-only
+ * @w1c: bits with the common write 1 to clear semantic.
+ * @reset: reset value.
+ * @cor: Bits that are clear on read
+ * @rsvd: Bits that are reserved and should not be changed
+ *
+ * @pre_write: Pre write callback. Passed the value that's to be written,
+ * immediately before the actual write. The returned value is what is written,
+ * giving the handler a chance to modify the written value.
+ * @post_write: Post write callback. Passed the written value. Most write side
+ * effects should be implemented here.
+ *
+ * @post_read: Post read callback. Passes the value that is about to be returned
+ * for a read. The return value from this function is what is ultimately read,
+ * allowing this function to modify the value before return to the client.
+ */
+
+struct RegisterAccessInfo {
+    const char *name;
+    uint64_t ro;
+    uint64_t w1c;
+    uint64_t reset;
+    uint64_t cor;
+    uint64_t rsvd;
+    uint64_t unimp;
+
+    uint64_t (*pre_write)(RegisterInfo *reg, uint64_t val);
+    void (*post_write)(RegisterInfo *reg, uint64_t val);
+
+    uint64_t (*post_read)(RegisterInfo *reg, uint64_t val);
+};
+
+/**
+ * A register that is part of guest accessible state
+ * @data: pointer to the register data. Will be cast
+ * to the relevant uint type depending on data_size.
+ * @data_size: Size of the register in bytes. Must be
+ * 1, 2, 4 or 8
+ *
+ * @access: Access description of this register
+ *
+ * @debug: Whether or not verbose debug is enabled
+ * @prefix: String prefix for log and debug messages
+ *
+ * @opaque: Opaque data for the register
+ */
+
+struct RegisterInfo {
+    /* <public> */
+    void *data;
+    int data_size;
+
+    const RegisterAccessInfo *access;
+
+    bool debug;
+    const char *prefix;
+
+    void *opaque;
+};
+
+/**
+ * write a value to a register, subject to its restrictions
+ * @reg: register to write to
+ * @val: value to write
+ * @we: write enable mask
+ */
+
+void register_write(RegisterInfo *reg, uint64_t val, uint64_t we);
+
+/**
+ * read a value from a register, subject to its restrictions
+ * @reg: register to read from
+ * returns: value read
+ */
+
+uint64_t register_read(RegisterInfo *reg);
+
+/**
+ * reset a register
+ * @reg: register to reset
+ */
+
+void register_reset(RegisterInfo *reg);
+
+#endif
