diff --git a/sound/ac97/bus.c b/sound/ac97/bus.c
new file mode 100644
index 0000000..31f858e
--- /dev/null
+++ b/sound/ac97/bus.c
@@ -0,0 +1,539 @@
+/*
+ * Copyright (C) 2016 Robert Jarzmik <robert.jarzmik@free.fr>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/idr.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/pm.h>
+#include <linux/pm_runtime.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <sound/ac97/codec.h>
+#include <sound/ac97/controller.h>
+#include <sound/ac97/regs.h>
+
+#include "ac97_core.h"
+
+/*
+ * Protects ac97_controllers and each ac97_controller structure.
+ */
+static DEFINE_MUTEX(ac97_controllers_mutex);
+static DEFINE_IDR(ac97_adapter_idr);
+static LIST_HEAD(ac97_controllers);
+
+static struct bus_type ac97_bus_type;
+
+static inline struct ac97_controller*
+to_ac97_controller(struct device *ac97_adapter)
+{
+	return container_of(ac97_adapter, struct ac97_controller, adap);
+}
+
+static int ac97_unbound_ctrl_write(struct ac97_controller *adrv, int slot,
+		     unsigned short reg, unsigned short val)
+{
+	return -ENODEV;
+}
+
+static int ac97_unbound_ctrl_read(struct ac97_controller *adrv, int slot,
+				  unsigned short reg)
+{
+	return -ENODEV;
+}
+
+static const struct ac97_controller_ops ac97_unbound_ctrl_ops = {
+	.write = ac97_unbound_ctrl_write,
+	.read = ac97_unbound_ctrl_read,
+};
+
+static struct ac97_controller ac97_unbound_ctrl = {
+	.ops = &ac97_unbound_ctrl_ops,
+};
+
+static struct ac97_codec_device *
+ac97_codec_find(struct ac97_controller *ac97_ctrl, unsigned int codec_num)
+{
+	if (codec_num >= AC97_BUS_MAX_CODECS)
+		return ERR_PTR(-EINVAL);
+
+	return ac97_ctrl->codecs[codec_num];
+}
+
+static void ac97_codec_release(struct device *dev)
+{
+	struct ac97_codec_device *adev;
+	struct ac97_controller *ac97_ctrl;
+
+	adev = to_ac97_device(dev);
+	ac97_ctrl = adev->ac97_ctrl;
+	ac97_ctrl->codecs[adev->num] = NULL;
+	kfree(adev);
+}
+
+static int ac97_codec_add(struct ac97_controller *ac97_ctrl, int idx,
+		   unsigned int vendor_id)
+{
+	struct ac97_codec_device *codec;
+	int ret;
+
+	codec = kzalloc(sizeof(*codec), GFP_KERNEL);
+	if (!codec)
+		return -ENOMEM;
+	ac97_ctrl->codecs[idx] = codec;
+	codec->vendor_id = vendor_id;
+	codec->dev.release = ac97_codec_release;
+	codec->dev.bus = &ac97_bus_type;
+	codec->dev.parent = &ac97_ctrl->adap;
+	codec->num = idx;
+	codec->ac97_ctrl = ac97_ctrl;
+
+	device_initialize(&codec->dev);
+	dev_set_name(&codec->dev, "%s:%u", dev_name(ac97_ctrl->parent), idx);
+
+	ret = device_add(&codec->dev);
+	if (ret)
+		goto err_free_codec;
+
+	return 0;
+err_free_codec:
+	put_device(&codec->dev);
+	kfree(codec);
+	ac97_ctrl->codecs[idx] = NULL;
+
+	return ret;
+}
+
+unsigned int snd_ac97_bus_scan_one(struct ac97_controller *adrv,
+				   unsigned int codec_num)
+{
+	unsigned short vid1, vid2;
+	int ret;
+
+	ret = adrv->ops->read(adrv, codec_num, AC97_VENDOR_ID1);
+	vid1 = (ret & 0xffff);
+	if (ret < 0)
+		return 0;
+
+	ret = adrv->ops->read(adrv, codec_num, AC97_VENDOR_ID2);
+	vid2 = (ret & 0xffff);
+	if (ret < 0)
+		return 0;
+
+	dev_dbg(&adrv->adap, "%s(codec_num=%u): vendor_id=0x%08x\n",
+		__func__, codec_num, AC97_ID(vid1, vid2));
+	return AC97_ID(vid1, vid2);
+}
+
+static int ac97_bus_scan(struct ac97_controller *ac97_ctrl)
+{
+	int ret, i;
+	unsigned int vendor_id;
+
+	for (i = 0; i < AC97_BUS_MAX_CODECS; i++) {
+		if (ac97_codec_find(ac97_ctrl, i))
+			continue;
+		if (!(ac97_ctrl->slots_available & BIT(i)))
+			continue;
+		vendor_id = snd_ac97_bus_scan_one(ac97_ctrl, i);
+		if (!vendor_id)
+			continue;
+
+		ret = ac97_codec_add(ac97_ctrl, i, vendor_id);
+		if (ret < 0)
+			return ret;
+	}
+	return 0;
+}
+
+static int ac97_bus_reset(struct ac97_controller *ac97_ctrl)
+{
+	ac97_ctrl->ops->reset(ac97_ctrl);
+
+	return 0;
+}
+
+/**
+ * snd_ac97_codec_driver_register - register an AC97 codec driver
+ * @dev: AC97 driver codec to register
+ *
+ * Register an AC97 codec driver to the ac97 bus driver, aka. the AC97 digital
+ * controller.
+ *
+ * Returns 0 on success or error code
+ */
+int snd_ac97_codec_driver_register(struct ac97_codec_driver *drv)
+{
+	drv->driver.bus = &ac97_bus_type;
+	return driver_register(&drv->driver);
+}
+EXPORT_SYMBOL_GPL(snd_ac97_codec_driver_register);
+
+/**
+ * snd_ac97_codec_driver_unregister - unregister an AC97 codec driver
+ * @dev: AC97 codec driver to unregister
+ *
+ * Unregister a previously registered ac97 codec driver.
+ */
+void snd_ac97_codec_driver_unregister(struct ac97_codec_driver *drv)
+{
+	driver_unregister(&drv->driver);
+}
+EXPORT_SYMBOL_GPL(snd_ac97_codec_driver_unregister);
+
+/**
+ * snd_ac97_codec_get_platdata - get platform_data
+ * @adev: the ac97 codec device
+ *
+ * For legacy platforms, in order to have platform_data in codec drivers
+ * available, while ac97 device are auto-created upon probe, this retrieves the
+ * platdata which was setup on ac97 controller registration.
+ *
+ * Returns the platform data pointer
+ */
+void *snd_ac97_codec_get_platdata(const struct ac97_codec_device *adev)
+{
+	struct ac97_controller *ac97_ctrl = adev->ac97_ctrl;
+
+	return ac97_ctrl->codecs_pdata[adev->num];
+}
+EXPORT_SYMBOL_GPL(snd_ac97_codec_get_platdata);
+
+static void ac97_ctrl_codecs_unregister(struct ac97_controller *ac97_ctrl)
+{
+	int i;
+
+	for (i = 0; i < AC97_BUS_MAX_CODECS; i++)
+		if (ac97_ctrl->codecs[i]) {
+			ac97_ctrl->codecs[i]->ac97_ctrl = &ac97_unbound_ctrl;
+			device_unregister(&ac97_ctrl->codecs[i]->dev);
+		}
+}
+
+static ssize_t cold_reset_store(struct device *dev,
+				struct device_attribute *attr, const char *buf,
+				size_t len)
+{
+	struct ac97_controller *ac97_ctrl;
+
+	mutex_lock(&ac97_controllers_mutex);
+	ac97_ctrl = to_ac97_controller(dev);
+	ac97_ctrl->ops->reset(ac97_ctrl);
+	mutex_unlock(&ac97_controllers_mutex);
+	return len;
+}
+static DEVICE_ATTR_WO(cold_reset);
+
+static ssize_t warm_reset_store(struct device *dev,
+				struct device_attribute *attr, const char *buf,
+				size_t len)
+{
+	struct ac97_controller *ac97_ctrl;
+
+	if (!dev)
+		return -ENODEV;
+
+	mutex_lock(&ac97_controllers_mutex);
+	ac97_ctrl = to_ac97_controller(dev);
+	ac97_ctrl->ops->warm_reset(ac97_ctrl);
+	mutex_unlock(&ac97_controllers_mutex);
+	return len;
+}
+static DEVICE_ATTR_WO(warm_reset);
+
+static struct attribute *ac97_controller_device_attrs[] = {
+	&dev_attr_cold_reset.attr,
+	&dev_attr_warm_reset.attr,
+	NULL
+};
+
+static struct attribute_group ac97_adapter_attr_group = {
+	.name	= "ac97_operations",
+	.attrs	= ac97_controller_device_attrs,
+};
+
+static const struct attribute_group *ac97_adapter_groups[] = {
+	&ac97_adapter_attr_group,
+	NULL,
+};
+
+static void ac97_del_adapter(struct ac97_controller *ac97_ctrl)
+{
+	mutex_lock(&ac97_controllers_mutex);
+	ac97_ctrl_codecs_unregister(ac97_ctrl);
+	list_del(&ac97_ctrl->controllers);
+	mutex_unlock(&ac97_controllers_mutex);
+
+	device_unregister(&ac97_ctrl->adap);
+}
+
+static void ac97_adapter_release(struct device *dev)
+{
+	struct ac97_controller *ac97_ctrl;
+
+	ac97_ctrl = to_ac97_controller(dev);
+	idr_remove(&ac97_adapter_idr, ac97_ctrl->nr);
+	dev_dbg(&ac97_ctrl->adap, "adapter unregistered by %s\n",
+		dev_name(ac97_ctrl->parent));
+}
+
+static const struct device_type ac97_adapter_type = {
+	.groups		= ac97_adapter_groups,
+	.release	= ac97_adapter_release,
+};
+
+static int ac97_add_adapter(struct ac97_controller *ac97_ctrl)
+{
+	int ret;
+
+	mutex_lock(&ac97_controllers_mutex);
+	ret = idr_alloc(&ac97_adapter_idr, ac97_ctrl, 0, 0, GFP_KERNEL);
+	ac97_ctrl->nr = ret;
+	if (ret >= 0) {
+		dev_set_name(&ac97_ctrl->adap, "ac97-%d", ret);
+		ac97_ctrl->adap.type = &ac97_adapter_type;
+		ac97_ctrl->adap.parent = ac97_ctrl->parent;
+		ret = device_register(&ac97_ctrl->adap);
+		if (ret)
+			put_device(&ac97_ctrl->adap);
+	}
+	if (!ret)
+		list_add(&ac97_ctrl->controllers, &ac97_controllers);
+	mutex_unlock(&ac97_controllers_mutex);
+
+	if (!ret)
+		dev_dbg(&ac97_ctrl->adap, "adapter registered by %s\n",
+			dev_name(ac97_ctrl->parent));
+	return ret;
+}
+
+/**
+ * snd_ac97_controller_register - register an ac97 controller
+ * @ops: the ac97 bus operations
+ * @dev: the device providing the ac97 DC function
+ * @slots_available: mask of the ac97 codecs that can be scanned and probed
+ *                   bit0 => codec 0, bit1 => codec 1 ... bit 3 => codec 3
+ *
+ * Register a digital controller which can control up to 4 ac97 codecs. This is
+ * the controller side of the AC97 AC-link, while the slave side are the codecs.
+ *
+ * Returns a valid controller upon success, negative pointer value upon error
+ */
+struct ac97_controller *snd_ac97_controller_register(
+	const struct ac97_controller_ops *ops, struct device *dev,
+	unsigned short slots_available, void **codecs_pdata)
+{
+	struct ac97_controller *ac97_ctrl;
+	int ret, i;
+
+	ac97_ctrl = kzalloc(sizeof(*ac97_ctrl), GFP_KERNEL);
+	if (!ac97_ctrl)
+		return ERR_PTR(-ENOMEM);
+
+	for (i = 0; i < AC97_BUS_MAX_CODECS && codecs_pdata; i++)
+		ac97_ctrl->codecs_pdata[i] = codecs_pdata[i];
+
+	ac97_ctrl->ops = ops;
+	ac97_ctrl->slots_available = slots_available;
+	ac97_ctrl->parent = dev;
+	ret = ac97_add_adapter(ac97_ctrl);
+
+	if (ret)
+		goto err;
+	ac97_bus_reset(ac97_ctrl);
+	ac97_bus_scan(ac97_ctrl);
+
+	return ac97_ctrl;
+err:
+	kfree(ac97_ctrl);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(snd_ac97_controller_register);
+
+/**
+ * snd_ac97_controller_unregister - unregister an ac97 controller
+ * @ac97_ctrl: the device previously provided to ac97_controller_register()
+ *
+ */
+void snd_ac97_controller_unregister(struct ac97_controller *ac97_ctrl)
+{
+	ac97_del_adapter(ac97_ctrl);
+}
+EXPORT_SYMBOL_GPL(snd_ac97_controller_unregister);
+
+#ifdef CONFIG_PM
+static int ac97_pm_runtime_suspend(struct device *dev)
+{
+	struct ac97_codec_device *codec = to_ac97_device(dev);
+	int ret = pm_generic_runtime_suspend(dev);
+
+	if (ret == 0 && dev->driver) {
+		if (pm_runtime_is_irq_safe(dev))
+			clk_disable(codec->clk);
+		else
+			clk_disable_unprepare(codec->clk);
+	}
+
+	return ret;
+}
+
+static int ac97_pm_runtime_resume(struct device *dev)
+{
+	struct ac97_codec_device *codec = to_ac97_device(dev);
+	int ret;
+
+	if (dev->driver) {
+		if (pm_runtime_is_irq_safe(dev))
+			ret = clk_enable(codec->clk);
+		else
+			ret = clk_prepare_enable(codec->clk);
+		if (ret)
+			return ret;
+	}
+
+	return pm_generic_runtime_resume(dev);
+}
+#endif /* CONFIG_PM */
+
+static const struct dev_pm_ops ac97_pm = {
+	.suspend	= pm_generic_suspend,
+	.resume		= pm_generic_resume,
+	.freeze		= pm_generic_freeze,
+	.thaw		= pm_generic_thaw,
+	.poweroff	= pm_generic_poweroff,
+	.restore	= pm_generic_restore,
+	SET_RUNTIME_PM_OPS(
+		ac97_pm_runtime_suspend,
+		ac97_pm_runtime_resume,
+		NULL)
+};
+
+static int ac97_get_enable_clk(struct ac97_codec_device *adev)
+{
+	int ret;
+
+	adev->clk = clk_get(&adev->dev, "ac97_clk");
+	if (IS_ERR(adev->clk))
+		return PTR_ERR(adev->clk);
+
+	ret = clk_prepare_enable(adev->clk);
+	if (ret)
+		clk_put(adev->clk);
+
+	return ret;
+}
+
+static void ac97_put_disable_clk(struct ac97_codec_device *adev)
+{
+	clk_disable_unprepare(adev->clk);
+	clk_put(adev->clk);
+}
+
+static ssize_t vendor_id_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	struct ac97_codec_device *codec = to_ac97_device(dev);
+
+	return sprintf(buf, "%08x", codec->vendor_id);
+}
+DEVICE_ATTR_RO(vendor_id);
+
+static struct attribute *ac97_dev_attrs[] = {
+	&dev_attr_vendor_id.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(ac97_dev);
+
+static int ac97_bus_match(struct device *dev, struct device_driver *drv)
+{
+	struct ac97_codec_device *adev = to_ac97_device(dev);
+	struct ac97_codec_driver *adrv = to_ac97_driver(drv);
+	const struct ac97_id *id = adrv->id_table;
+	int i = 0;
+
+	if (adev->vendor_id == 0x0 || adev->vendor_id == 0xffffffff)
+		return false;
+
+	do {
+		if (ac97_ids_match(id[i].id, adev->vendor_id, id[i].mask))
+			return true;
+	} while (id[i++].id);
+
+	return false;
+}
+
+static int ac97_bus_probe(struct device *dev)
+{
+	struct ac97_codec_device *adev = to_ac97_device(dev);
+	struct ac97_codec_driver *adrv = to_ac97_driver(dev->driver);
+	int ret;
+
+	ret = ac97_get_enable_clk(adev);
+	if (ret)
+		return ret;
+
+	pm_runtime_get_noresume(dev);
+	pm_runtime_set_active(dev);
+	pm_runtime_enable(dev);
+
+	ret = adrv->probe(adev);
+	if (ret == 0)
+		return 0;
+
+	pm_runtime_disable(dev);
+	pm_runtime_set_suspended(dev);
+	pm_runtime_put_noidle(dev);
+	ac97_put_disable_clk(adev);
+
+	return ret;
+}
+
+static int ac97_bus_remove(struct device *dev)
+{
+	struct ac97_codec_device *adev = to_ac97_device(dev);
+	struct ac97_codec_driver *adrv = to_ac97_driver(dev->driver);
+	int ret;
+
+	ret = pm_runtime_get_sync(dev);
+	if (ret)
+		return ret;
+
+	ret = adrv->remove(adev);
+	pm_runtime_put_noidle(dev);
+	if (ret == 0)
+		ac97_put_disable_clk(adev);
+
+	return ret;
+}
+
+static struct bus_type ac97_bus_type = {
+	.name		= "ac97bus",
+	.dev_groups	= ac97_dev_groups,
+	.match		= ac97_bus_match,
+	.pm		= &ac97_pm,
+	.probe		= ac97_bus_probe,
+	.remove		= ac97_bus_remove,
+};
+
+static int __init ac97_bus_init(void)
+{
+	return bus_register(&ac97_bus_type);
+}
+subsys_initcall(ac97_bus_init);
+
+static void __exit ac97_bus_exit(void)
+{
+	bus_unregister(&ac97_bus_type);
+}
+module_exit(ac97_bus_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Robert Jarzmik <robert.jarzmik@free.fr>");