drivers/gpu/drm/drm_dp_aux_dev.c - kernel/quantenna - Git at Google

 /*
  * Copyright © 2015 Intel Corporation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
  * to deal in the Software without restriction, including without limitation
  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  * and/or sell copies of the Software, and to permit persons to whom the
  * Software is furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice (including the next
  * paragraph) shall be included in all copies or substantial portions of the
  * Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  * IN THE SOFTWARE.
  *
  * Authors:
  *    Rafael Antognolli <rafael.antognolli@intel.com>
  *
  */

 #include <linux/device.h>
 #include <linux/fs.h>
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/uaccess.h>
 #include <drm/drm_dp_helper.h>
 #include <drm/drm_crtc.h>
 #include <drm/drmP.h>

 struct drm_dp_aux_dev {
 	unsigned index;
 	struct drm_dp_aux *aux;
 	struct device *dev;
 	struct kref refcount;
 	atomic_t usecount;
 };

 #define DRM_AUX_MINORS	256
 #define AUX_MAX_OFFSET	(1 << 20)
 static DEFINE_IDR(aux_idr);
 static DEFINE_MUTEX(aux_idr_mutex);
 static struct class *drm_dp_aux_dev_class;
 static int drm_dev_major = -1;

 static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_minor(unsigned index)
 {
 	struct drm_dp_aux_dev *aux_dev = NULL;

 	mutex_lock(&aux_idr_mutex);
 	aux_dev = idr_find(&aux_idr, index);
 	if (!kref_get_unless_zero(&aux_dev->refcount))
 		aux_dev = NULL;
 	mutex_unlock(&aux_idr_mutex);

 	return aux_dev;
 }

 static struct drm_dp_aux_dev *alloc_drm_dp_aux_dev(struct drm_dp_aux *aux)
 {
 	struct drm_dp_aux_dev *aux_dev;
 	int index;

 	aux_dev = kzalloc(sizeof(*aux_dev), GFP_KERNEL);
 	if (!aux_dev)
 		return ERR_PTR(-ENOMEM);
 	aux_dev->aux = aux;
 	atomic_set(&aux_dev->usecount, 1);
 	kref_init(&aux_dev->refcount);

 	mutex_lock(&aux_idr_mutex);
 	index = idr_alloc_cyclic(&aux_idr, aux_dev, 0, DRM_AUX_MINORS,
 				 GFP_KERNEL);
 	mutex_unlock(&aux_idr_mutex);
 	if (index < 0) {
 		kfree(aux_dev);
 		return ERR_PTR(index);
 	}
 	aux_dev->index = index;

 	return aux_dev;
 }

 static void release_drm_dp_aux_dev(struct kref *ref)
 {
 	struct drm_dp_aux_dev *aux_dev =
 		container_of(ref, struct drm_dp_aux_dev, refcount);

 	kfree(aux_dev);
 }

 static ssize_t name_show(struct device *dev,
 			 struct device_attribute *attr, char *buf)
 {
 	ssize_t res;
 	struct drm_dp_aux_dev *aux_dev =
 		drm_dp_aux_dev_get_by_minor(MINOR(dev->devt));

 	if (!aux_dev)
 		return -ENODEV;

 	res = sprintf(buf, "%s\n", aux_dev->aux->name);
 	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);

 	return res;
 }
 static DEVICE_ATTR_RO(name);

 static struct attribute *drm_dp_aux_attrs[] = {
 	&dev_attr_name.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(drm_dp_aux);

 static int auxdev_open(struct inode *inode, struct file *file)
 {
 	unsigned int minor = iminor(inode);
 	struct drm_dp_aux_dev *aux_dev;

 	aux_dev = drm_dp_aux_dev_get_by_minor(minor);
 	if (!aux_dev)
 		return -ENODEV;

 	file->private_data = aux_dev;
 	return 0;
 }

 static loff_t auxdev_llseek(struct file *file, loff_t offset, int whence)
 {
 	return fixed_size_llseek(file, offset, whence, AUX_MAX_OFFSET);
 }

 static ssize_t auxdev_read(struct file *file, char __user *buf, size_t count,
 			   loff_t *offset)
 {
 	size_t bytes_pending, num_bytes_processed = 0;
 	struct drm_dp_aux_dev *aux_dev = file->private_data;
 	ssize_t res = 0;

 	if (!atomic_inc_not_zero(&aux_dev->usecount))
 		return -ENODEV;

 	bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - (*offset));

 	if (!access_ok(VERIFY_WRITE, buf, bytes_pending)) {
 		res = -EFAULT;
 		goto out;
 	}

 	while (bytes_pending > 0) {
 		uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
 		ssize_t todo = min_t(size_t, bytes_pending, sizeof(localbuf));

 		if (signal_pending(current)) {
 			res = num_bytes_processed ?
 				num_bytes_processed : -ERESTARTSYS;
 			goto out;
 		}

 		res = drm_dp_dpcd_read(aux_dev->aux, *offset, localbuf, todo);
 		if (res <= 0) {
 			res = num_bytes_processed ? num_bytes_processed : res;
 			goto out;
 		}
 		if (__copy_to_user(buf + num_bytes_processed, localbuf, res)) {
 			res = num_bytes_processed ?
 				num_bytes_processed : -EFAULT;
 			goto out;
 		}
 		bytes_pending -= res;
 		*offset += res;
 		num_bytes_processed += res;
 		res = num_bytes_processed;
 	}

 out:
 	atomic_dec(&aux_dev->usecount);
 	wake_up_atomic_t(&aux_dev->usecount);
 	return res;
 }

 static ssize_t auxdev_write(struct file *file, const char __user *buf,
 			    size_t count, loff_t *offset)
 {
 	size_t bytes_pending, num_bytes_processed = 0;
 	struct drm_dp_aux_dev *aux_dev = file->private_data;
 	ssize_t res = 0;

 	if (!atomic_inc_not_zero(&aux_dev->usecount))
 		return -ENODEV;

 	bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - *offset);

 	if (!access_ok(VERIFY_READ, buf, bytes_pending)) {
 		res = -EFAULT;
 		goto out;
 	}

 	while (bytes_pending > 0) {
 		uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
 		ssize_t todo = min_t(size_t, bytes_pending, sizeof(localbuf));

 		if (signal_pending(current)) {
 			res = num_bytes_processed ?
 				num_bytes_processed : -ERESTARTSYS;
 			goto out;
 		}

 		if (__copy_from_user(localbuf,
 				     buf + num_bytes_processed, todo)) {
 			res = num_bytes_processed ?
 				num_bytes_processed : -EFAULT;
 			goto out;
 		}

 		res = drm_dp_dpcd_write(aux_dev->aux, *offset, localbuf, todo);
 		if (res <= 0) {
 			res = num_bytes_processed ? num_bytes_processed : res;
 			goto out;
 		}
 		bytes_pending -= res;
 		*offset += res;
 		num_bytes_processed += res;
 		res = num_bytes_processed;
 	}

 out:
 	atomic_dec(&aux_dev->usecount);
 	wake_up_atomic_t(&aux_dev->usecount);
 	return res;
 }

 static int auxdev_release(struct inode *inode, struct file *file)
 {
 	struct drm_dp_aux_dev *aux_dev = file->private_data;

 	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
 	return 0;
 }

 static const struct file_operations auxdev_fops = {
 	.owner		= THIS_MODULE,
 	.llseek		= auxdev_llseek,
 	.read		= auxdev_read,
 	.write		= auxdev_write,
 	.open		= auxdev_open,
 	.release	= auxdev_release,
 };

 #define to_auxdev(d) container_of(d, struct drm_dp_aux_dev, aux)

 static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
 {
 	struct drm_dp_aux_dev *iter, *aux_dev = NULL;
 	int id;

 	/* don't increase kref count here because this function should only be
 	 * used by drm_dp_aux_unregister_devnode. Thus, it will always have at
 	 * least one reference - the one that drm_dp_aux_register_devnode
 	 * created
 	 */
 	mutex_lock(&aux_idr_mutex);
 	idr_for_each_entry(&aux_idr, iter, id) {
 		if (iter->aux == aux) {
 			aux_dev = iter;
 			break;
 		}
 	}
 	mutex_unlock(&aux_idr_mutex);
 	return aux_dev;
 }

 static int auxdev_wait_atomic_t(atomic_t *p)
 {
 	schedule();
 	return 0;
 }
 /**
  * drm_dp_aux_unregister_devnode() - unregister a devnode for this aux channel
  * @aux: DisplayPort AUX channel
  *
  * Returns 0 on success or a negative error code on failure.
  */
 void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
 {
 	struct drm_dp_aux_dev *aux_dev;
 	unsigned int minor;

 	aux_dev = drm_dp_aux_dev_get_by_aux(aux);
 	if (!aux_dev) /* attach must have failed */
 		return;

 	mutex_lock(&aux_idr_mutex);
 	idr_remove(&aux_idr, aux_dev->index);
 	mutex_unlock(&aux_idr_mutex);

 	atomic_dec(&aux_dev->usecount);
 	wait_on_atomic_t(&aux_dev->usecount, auxdev_wait_atomic_t,
 			 TASK_UNINTERRUPTIBLE);

 	minor = aux_dev->index;
 	if (aux_dev->dev)
 		device_destroy(drm_dp_aux_dev_class,
 			       MKDEV(drm_dev_major, minor));

 	DRM_DEBUG("drm_dp_aux_dev: aux [%s] unregistering\n", aux->name);
 	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
 }
 EXPORT_SYMBOL(drm_dp_aux_unregister_devnode);

 /**
  * drm_dp_aux_register_devnode() - register a devnode for this aux channel
  * @aux: DisplayPort AUX channel
  *
  * Returns 0 on success or a negative error code on failure.
  */
 int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
 {
 	struct drm_dp_aux_dev *aux_dev;
 	int res;

 	aux_dev = alloc_drm_dp_aux_dev(aux);
 	if (IS_ERR(aux_dev))
 		return PTR_ERR(aux_dev);

 	aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
 				     MKDEV(drm_dev_major, aux_dev->index), NULL,
 				     "drm_dp_aux%d", aux_dev->index);
 	if (IS_ERR(aux_dev->dev)) {
 		res = PTR_ERR(aux_dev->dev);
 		aux_dev->dev = NULL;
 		goto error;
 	}

 	DRM_DEBUG("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
 		  aux->name, aux_dev->index);
 	return 0;
 error:
 	drm_dp_aux_unregister_devnode(aux);
 	return res;
 }
 EXPORT_SYMBOL(drm_dp_aux_register_devnode);

 int drm_dp_aux_dev_init(void)
 {
 	int res;

 	drm_dp_aux_dev_class = class_create(THIS_MODULE, "drm_dp_aux_dev");
 	if (IS_ERR(drm_dp_aux_dev_class)) {
 		res = PTR_ERR(drm_dp_aux_dev_class);
 		goto out;
 	}
 	drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;

 	res = register_chrdev(0, "aux", &auxdev_fops);
 	if (res < 0)
 		goto out;
 	drm_dev_major = res;

 	return 0;
 out:
 	class_destroy(drm_dp_aux_dev_class);
 	return res;
 }
 EXPORT_SYMBOL(drm_dp_aux_dev_init);

 void drm_dp_aux_dev_exit(void)
 {
 	unregister_chrdev(drm_dev_major, "aux");
 	class_destroy(drm_dp_aux_dev_class);
 }
 EXPORT_SYMBOL(drm_dp_aux_dev_exit);
	/*
	* Copyright © 2015 Intel Corporation
	*
	* Permission is hereby granted, free of charge, to any person obtaining a
	* copy of this software and associated documentation files (the "Software"),
	* to deal in the Software without restriction, including without limitation
	* the rights to use, copy, modify, merge, publish, distribute, sublicense,
	* and/or sell copies of the Software, and to permit persons to whom the
	* Software is furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice (including the next
	* paragraph) shall be included in all copies or substantial portions of the
	* Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
	* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
	* IN THE SOFTWARE.
	*
	* Authors:
	* Rafael Antognolli <rafael.antognolli@intel.com>
	*
	*/

	#include <linux/device.h>
	#include <linux/fs.h>
	#include <linux/slab.h>
	#include <linux/init.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/uaccess.h>
	#include <drm/drm_dp_helper.h>
	#include <drm/drm_crtc.h>
	#include <drm/drmP.h>

	struct drm_dp_aux_dev {
	unsigned index;
	struct drm_dp_aux *aux;
	struct device *dev;
	struct kref refcount;
	atomic_t usecount;
	};

	#define DRM_AUX_MINORS 256
	#define AUX_MAX_OFFSET (1 << 20)
	static DEFINE_IDR(aux_idr);
	static DEFINE_MUTEX(aux_idr_mutex);
	static struct class *drm_dp_aux_dev_class;
	static int drm_dev_major = -1;

	static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_minor(unsigned index)
	{
	struct drm_dp_aux_dev *aux_dev = NULL;

	mutex_lock(&aux_idr_mutex);
	aux_dev = idr_find(&aux_idr, index);
	if (!kref_get_unless_zero(&aux_dev->refcount))
	aux_dev = NULL;
	mutex_unlock(&aux_idr_mutex);

	return aux_dev;
	}

	static struct drm_dp_aux_dev alloc_drm_dp_aux_dev(struct drm_dp_aux aux)
	{
	struct drm_dp_aux_dev *aux_dev;
	int index;

	aux_dev = kzalloc(sizeof(*aux_dev), GFP_KERNEL);
	if (!aux_dev)
	return ERR_PTR(-ENOMEM);
	aux_dev->aux = aux;
	atomic_set(&aux_dev->usecount, 1);
	kref_init(&aux_dev->refcount);

	mutex_lock(&aux_idr_mutex);
	index = idr_alloc_cyclic(&aux_idr, aux_dev, 0, DRM_AUX_MINORS,
	GFP_KERNEL);
	mutex_unlock(&aux_idr_mutex);
	if (index < 0) {
	kfree(aux_dev);
	return ERR_PTR(index);
	}
	aux_dev->index = index;

	return aux_dev;
	}

	static void release_drm_dp_aux_dev(struct kref *ref)
	{
	struct drm_dp_aux_dev *aux_dev =
	container_of(ref, struct drm_dp_aux_dev, refcount);

	kfree(aux_dev);
	}

	static ssize_t name_show(struct device *dev,
	struct device_attribute attr, char buf)
	{
	ssize_t res;
	struct drm_dp_aux_dev *aux_dev =
	drm_dp_aux_dev_get_by_minor(MINOR(dev->devt));

	if (!aux_dev)
	return -ENODEV;

	res = sprintf(buf, "%s\n", aux_dev->aux->name);
	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);

	return res;
	}
	static DEVICE_ATTR_RO(name);

	static struct attribute *drm_dp_aux_attrs[] = {
	&dev_attr_name.attr,
	NULL,
	};
	ATTRIBUTE_GROUPS(drm_dp_aux);

	static int auxdev_open(struct inode inode, struct file file)
	{
	unsigned int minor = iminor(inode);
	struct drm_dp_aux_dev *aux_dev;

	aux_dev = drm_dp_aux_dev_get_by_minor(minor);
	if (!aux_dev)
	return -ENODEV;

	file->private_data = aux_dev;
	return 0;
	}

	static loff_t auxdev_llseek(struct file *file, loff_t offset, int whence)
	{
	return fixed_size_llseek(file, offset, whence, AUX_MAX_OFFSET);
	}

	static ssize_t auxdev_read(struct file file, char __user buf, size_t count,
	loff_t *offset)
	{
	size_t bytes_pending, num_bytes_processed = 0;
	struct drm_dp_aux_dev *aux_dev = file->private_data;
	ssize_t res = 0;

	if (!atomic_inc_not_zero(&aux_dev->usecount))
	return -ENODEV;

	bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - (*offset));

	if (!access_ok(VERIFY_WRITE, buf, bytes_pending)) {
	res = -EFAULT;
	goto out;
	}

	while (bytes_pending > 0) {
	uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
	ssize_t todo = min_t(size_t, bytes_pending, sizeof(localbuf));

	if (signal_pending(current)) {
	res = num_bytes_processed ?
	num_bytes_processed : -ERESTARTSYS;
	goto out;
	}

	res = drm_dp_dpcd_read(aux_dev->aux, *offset, localbuf, todo);
	if (res <= 0) {
	res = num_bytes_processed ? num_bytes_processed : res;
	goto out;
	}
	if (__copy_to_user(buf + num_bytes_processed, localbuf, res)) {
	res = num_bytes_processed ?
	num_bytes_processed : -EFAULT;
	goto out;
	}
	bytes_pending -= res;
	*offset += res;
	num_bytes_processed += res;
	res = num_bytes_processed;
	}

	out:
	atomic_dec(&aux_dev->usecount);
	wake_up_atomic_t(&aux_dev->usecount);
	return res;
	}

	static ssize_t auxdev_write(struct file file, const char __user buf,
	size_t count, loff_t *offset)
	{
	size_t bytes_pending, num_bytes_processed = 0;
	struct drm_dp_aux_dev *aux_dev = file->private_data;
	ssize_t res = 0;

	if (!atomic_inc_not_zero(&aux_dev->usecount))
	return -ENODEV;

	bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - *offset);

	if (!access_ok(VERIFY_READ, buf, bytes_pending)) {
	res = -EFAULT;
	goto out;
	}

	while (bytes_pending > 0) {
	uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
	ssize_t todo = min_t(size_t, bytes_pending, sizeof(localbuf));

	if (signal_pending(current)) {
	res = num_bytes_processed ?
	num_bytes_processed : -ERESTARTSYS;
	goto out;
	}

	if (__copy_from_user(localbuf,
	buf + num_bytes_processed, todo)) {
	res = num_bytes_processed ?
	num_bytes_processed : -EFAULT;
	goto out;
	}

	res = drm_dp_dpcd_write(aux_dev->aux, *offset, localbuf, todo);
	if (res <= 0) {
	res = num_bytes_processed ? num_bytes_processed : res;
	goto out;
	}
	bytes_pending -= res;
	*offset += res;
	num_bytes_processed += res;
	res = num_bytes_processed;
	}

	out:
	atomic_dec(&aux_dev->usecount);
	wake_up_atomic_t(&aux_dev->usecount);
	return res;
	}

	static int auxdev_release(struct inode inode, struct file file)
	{
	struct drm_dp_aux_dev *aux_dev = file->private_data;

	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
	return 0;
	}

	static const struct file_operations auxdev_fops = {
	.owner = THIS_MODULE,
	.llseek = auxdev_llseek,
	.read = auxdev_read,
	.write = auxdev_write,
	.open = auxdev_open,
	.release = auxdev_release,
	};

	#define to_auxdev(d) container_of(d, struct drm_dp_aux_dev, aux)

	static struct drm_dp_aux_dev drm_dp_aux_dev_get_by_aux(struct drm_dp_aux aux)
	{
	struct drm_dp_aux_dev iter, aux_dev = NULL;
	int id;

	/* don't increase kref count here because this function should only be
	* used by drm_dp_aux_unregister_devnode. Thus, it will always have at
	* least one reference - the one that drm_dp_aux_register_devnode
	* created
	*/
	mutex_lock(&aux_idr_mutex);
	idr_for_each_entry(&aux_idr, iter, id) {
	if (iter->aux == aux) {
	aux_dev = iter;
	break;
	}
	}
	mutex_unlock(&aux_idr_mutex);
	return aux_dev;
	}

	static int auxdev_wait_atomic_t(atomic_t *p)
	{
	schedule();
	return 0;
	}
	/**
	* drm_dp_aux_unregister_devnode() - unregister a devnode for this aux channel
	* @aux: DisplayPort AUX channel
	*
	* Returns 0 on success or a negative error code on failure.
	*/
	void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
	{
	struct drm_dp_aux_dev *aux_dev;
	unsigned int minor;

	aux_dev = drm_dp_aux_dev_get_by_aux(aux);
	if (!aux_dev) /* attach must have failed */
	return;

	mutex_lock(&aux_idr_mutex);
	idr_remove(&aux_idr, aux_dev->index);
	mutex_unlock(&aux_idr_mutex);

	atomic_dec(&aux_dev->usecount);
	wait_on_atomic_t(&aux_dev->usecount, auxdev_wait_atomic_t,
	TASK_UNINTERRUPTIBLE);

	minor = aux_dev->index;
	if (aux_dev->dev)
	device_destroy(drm_dp_aux_dev_class,
	MKDEV(drm_dev_major, minor));

	DRM_DEBUG("drm_dp_aux_dev: aux [%s] unregistering\n", aux->name);
	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
	}
	EXPORT_SYMBOL(drm_dp_aux_unregister_devnode);

	/**
	* drm_dp_aux_register_devnode() - register a devnode for this aux channel
	* @aux: DisplayPort AUX channel
	*
	* Returns 0 on success or a negative error code on failure.
	*/
	int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
	{
	struct drm_dp_aux_dev *aux_dev;
	int res;

	aux_dev = alloc_drm_dp_aux_dev(aux);
	if (IS_ERR(aux_dev))
	return PTR_ERR(aux_dev);

	aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
	MKDEV(drm_dev_major, aux_dev->index), NULL,
	"drm_dp_aux%d", aux_dev->index);
	if (IS_ERR(aux_dev->dev)) {
	res = PTR_ERR(aux_dev->dev);
	aux_dev->dev = NULL;
	goto error;
	}

	DRM_DEBUG("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
	aux->name, aux_dev->index);
	return 0;
	error:
	drm_dp_aux_unregister_devnode(aux);
	return res;
	}
	EXPORT_SYMBOL(drm_dp_aux_register_devnode);

	int drm_dp_aux_dev_init(void)
	{
	int res;

	drm_dp_aux_dev_class = class_create(THIS_MODULE, "drm_dp_aux_dev");
	if (IS_ERR(drm_dp_aux_dev_class)) {
	res = PTR_ERR(drm_dp_aux_dev_class);
	goto out;
	}
	drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;

	res = register_chrdev(0, "aux", &auxdev_fops);
	if (res < 0)
	goto out;
	drm_dev_major = res;

	return 0;
	out:
	class_destroy(drm_dp_aux_dev_class);
	return res;
	}
	EXPORT_SYMBOL(drm_dp_aux_dev_init);

	void drm_dp_aux_dev_exit(void)
	{
	unregister_chrdev(drm_dev_major, "aux");
	class_destroy(drm_dp_aux_dev_class);
	}
	EXPORT_SYMBOL(drm_dp_aux_dev_exit);