drivers/media/media-devnode.c - maze/linux - Git at Google

 /*
  * Media device node
  *
  * Copyright (C) 2010 Nokia Corporation
  *
  * Based on drivers/media/video/v4l2_dev.c code authored by
  *	Mauro Carvalho Chehab <mchehab@infradead.org> (version 2)
  *	Alan Cox, <alan@lxorguk.ukuu.org.uk> (version 1)
  *
  * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
  *	     Sakari Ailus <sakari.ailus@iki.fi>
  *
  * 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.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  *
  * --
  *
  * Generic media device node infrastructure to register and unregister
  * character devices using a dynamic major number and proper reference
  * counting.
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/errno.h>
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/kmod.h>
 #include <linux/slab.h>
 #include <linux/mm.h>
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/uaccess.h>

 #include <media/media-devnode.h>

 #define MEDIA_NUM_DEVICES	256
 #define MEDIA_NAME		"media"

 static dev_t media_dev_t;

 /*
  *	Active devices
  */
 static DEFINE_MUTEX(media_devnode_lock);
 static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);

 /* Called when the last user of the media device exits. */
 static void media_devnode_release(struct device *cd)
 {
 	struct media_devnode *mdev = to_media_devnode(cd);

 	mutex_lock(&media_devnode_lock);

 	/* Delete the cdev on this minor as well */
 	cdev_del(&mdev->cdev);

 	/* Mark device node number as free */
 	clear_bit(mdev->minor, media_devnode_nums);

 	mutex_unlock(&media_devnode_lock);

 	/* Release media_devnode and perform other cleanups as needed. */
 	if (mdev->release)
 		mdev->release(mdev);
 }

 static struct bus_type media_bus_type = {
 	.name = MEDIA_NAME,
 };

 static ssize_t media_read(struct file *filp, char __user *buf,
 		size_t sz, loff_t *off)
 {
 	struct media_devnode *mdev = media_devnode_data(filp);

 	if (!mdev->fops->read)
 		return -EINVAL;
 	if (!media_devnode_is_registered(mdev))
 		return -EIO;
 	return mdev->fops->read(filp, buf, sz, off);
 }

 static ssize_t media_write(struct file *filp, const char __user *buf,
 		size_t sz, loff_t *off)
 {
 	struct media_devnode *mdev = media_devnode_data(filp);

 	if (!mdev->fops->write)
 		return -EINVAL;
 	if (!media_devnode_is_registered(mdev))
 		return -EIO;
 	return mdev->fops->write(filp, buf, sz, off);
 }

 static unsigned int media_poll(struct file *filp,
 			       struct poll_table_struct *poll)
 {
 	struct media_devnode *mdev = media_devnode_data(filp);

 	if (!media_devnode_is_registered(mdev))
 		return POLLERR | POLLHUP;
 	if (!mdev->fops->poll)
 		return DEFAULT_POLLMASK;
 	return mdev->fops->poll(filp, poll);
 }

 static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	struct media_devnode *mdev = media_devnode_data(filp);

 	if (!mdev->fops->ioctl)
 		return -ENOTTY;

 	if (!media_devnode_is_registered(mdev))
 		return -EIO;

 	return mdev->fops->ioctl(filp, cmd, arg);
 }

 /* Override for the open function */
 static int media_open(struct inode *inode, struct file *filp)
 {
 	struct media_devnode *mdev;
 	int ret;

 	/* Check if the media device is available. This needs to be done with
 	 * the media_devnode_lock held to prevent an open/unregister race:
 	 * without the lock, the device could be unregistered and freed between
 	 * the media_devnode_is_registered() and get_device() calls, leading to
 	 * a crash.
 	 */
 	mutex_lock(&media_devnode_lock);
 	mdev = container_of(inode->i_cdev, struct media_devnode, cdev);
 	/* return ENXIO if the media device has been removed
 	   already or if it is not registered anymore. */
 	if (!media_devnode_is_registered(mdev)) {
 		mutex_unlock(&media_devnode_lock);
 		return -ENXIO;
 	}
 	/* and increase the device refcount */
 	get_device(&mdev->dev);
 	mutex_unlock(&media_devnode_lock);

 	filp->private_data = mdev;

 	if (mdev->fops->open) {
 		ret = mdev->fops->open(filp);
 		if (ret) {
 			put_device(&mdev->dev);
 			return ret;
 		}
 	}

 	return 0;
 }

 /* Override for the release function */
 static int media_release(struct inode *inode, struct file *filp)
 {
 	struct media_devnode *mdev = media_devnode_data(filp);
 	int ret = 0;

 	if (mdev->fops->release)
 		mdev->fops->release(filp);

 	/* decrease the refcount unconditionally since the release()
 	   return value is ignored. */
 	put_device(&mdev->dev);
 	filp->private_data = NULL;
 	return ret;
 }

 static const struct file_operations media_devnode_fops = {
 	.owner = THIS_MODULE,
 	.read = media_read,
 	.write = media_write,
 	.open = media_open,
 	.unlocked_ioctl = media_ioctl,
 	.release = media_release,
 	.poll = media_poll,
 	.llseek = no_llseek,
 };

 /**
  * media_devnode_register - register a media device node
  * @mdev: media device node structure we want to register
  *
  * The registration code assigns minor numbers and registers the new device node
  * with the kernel. An error is returned if no free minor number can be found,
  * or if the registration of the device node fails.
  *
  * Zero is returned on success.
  *
  * Note that if the media_devnode_register call fails, the release() callback of
  * the media_devnode structure is *not* called, so the caller is responsible for
  * freeing any data.
  */
 int __must_check media_devnode_register(struct media_devnode *mdev)
 {
 	int minor;
 	int ret;

 	/* Part 1: Find a free minor number */
 	mutex_lock(&media_devnode_lock);
 	minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
 	if (minor == MEDIA_NUM_DEVICES) {
 		mutex_unlock(&media_devnode_lock);
 		pr_err("could not get a free minor\n");
 		return -ENFILE;
 	}

 	set_bit(minor, media_devnode_nums);
 	mutex_unlock(&media_devnode_lock);

 	mdev->minor = minor;

 	/* Part 2: Initialize and register the character device */
 	cdev_init(&mdev->cdev, &media_devnode_fops);
 	mdev->cdev.owner = mdev->fops->owner;

 	ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1);
 	if (ret < 0) {
 		pr_err("%s: cdev_add failed\n", __func__);
 		goto error;
 	}

 	/* Part 3: Register the media device */
 	mdev->dev.bus = &media_bus_type;
 	mdev->dev.devt = MKDEV(MAJOR(media_dev_t), mdev->minor);
 	mdev->dev.release = media_devnode_release;
 	if (mdev->parent)
 		mdev->dev.parent = mdev->parent;
 	dev_set_name(&mdev->dev, "media%d", mdev->minor);
 	ret = device_register(&mdev->dev);
 	if (ret < 0) {
 		pr_err("%s: device_register failed\n", __func__);
 		goto error;
 	}

 	/* Part 4: Activate this minor. The char device can now be used. */
 	set_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);

 	return 0;

 error:
 	cdev_del(&mdev->cdev);
 	clear_bit(mdev->minor, media_devnode_nums);
 	return ret;
 }

 /**
  * media_devnode_unregister - unregister a media device node
  * @mdev: the device node to unregister
  *
  * This unregisters the passed device. Future open calls will be met with
  * errors.
  *
  * This function can safely be called if the device node has never been
  * registered or has already been unregistered.
  */
 void media_devnode_unregister(struct media_devnode *mdev)
 {
 	/* Check if mdev was ever registered at all */
 	if (!media_devnode_is_registered(mdev))
 		return;

 	mutex_lock(&media_devnode_lock);
 	clear_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
 	mutex_unlock(&media_devnode_lock);
 	device_unregister(&mdev->dev);
 }

 /*
  *	Initialise media for linux
  */
 static int __init media_devnode_init(void)
 {
 	int ret;

 	pr_info("Linux media interface: v0.10\n");
 	ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
 				  MEDIA_NAME);
 	if (ret < 0) {
 		pr_warn("unable to allocate major\n");
 		return ret;
 	}

 	ret = bus_register(&media_bus_type);
 	if (ret < 0) {
 		unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
 		pr_warn("bus_register failed\n");
 		return -EIO;
 	}

 	return 0;
 }

 static void __exit media_devnode_exit(void)
 {
 	bus_unregister(&media_bus_type);
 	unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
 }

 subsys_initcall(media_devnode_init);
 module_exit(media_devnode_exit)

 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
 MODULE_DESCRIPTION("Device node registration for media drivers");
 MODULE_LICENSE("GPL");
	/*
	* Media device node
	*
	* Copyright (C) 2010 Nokia Corporation
	*
	* Based on drivers/media/video/v4l2_dev.c code authored by
	* Mauro Carvalho Chehab <mchehab@infradead.org> (version 2)
	* Alan Cox, <alan@lxorguk.ukuu.org.uk> (version 1)
	*
	* Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
	* Sakari Ailus <sakari.ailus@iki.fi>
	*
	* 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.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	*
	* --
	*
	* Generic media device node infrastructure to register and unregister
	* character devices using a dynamic major number and proper reference
	* counting.
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/errno.h>
	#include <linux/init.h>
	#include <linux/module.h>
	#include <linux/kernel.h>
	#include <linux/kmod.h>
	#include <linux/slab.h>
	#include <linux/mm.h>
	#include <linux/string.h>
	#include <linux/types.h>
	#include <linux/uaccess.h>

	#include <media/media-devnode.h>

	#define MEDIA_NUM_DEVICES 256
	#define MEDIA_NAME "media"

	static dev_t media_dev_t;

	/*
	* Active devices
	*/
	static DEFINE_MUTEX(media_devnode_lock);
	static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);

	/* Called when the last user of the media device exits. */
	static void media_devnode_release(struct device *cd)
	{
	struct media_devnode *mdev = to_media_devnode(cd);

	mutex_lock(&media_devnode_lock);

	/* Delete the cdev on this minor as well */
	cdev_del(&mdev->cdev);

	/* Mark device node number as free */
	clear_bit(mdev->minor, media_devnode_nums);

	mutex_unlock(&media_devnode_lock);

	/* Release media_devnode and perform other cleanups as needed. */
	if (mdev->release)
	mdev->release(mdev);
	}

	static struct bus_type media_bus_type = {
	.name = MEDIA_NAME,
	};

	static ssize_t media_read(struct file filp, char __user buf,
	size_t sz, loff_t *off)
	{
	struct media_devnode *mdev = media_devnode_data(filp);

	if (!mdev->fops->read)
	return -EINVAL;
	if (!media_devnode_is_registered(mdev))
	return -EIO;
	return mdev->fops->read(filp, buf, sz, off);
	}

	static ssize_t media_write(struct file filp, const char __user buf,
	size_t sz, loff_t *off)
	{
	struct media_devnode *mdev = media_devnode_data(filp);

	if (!mdev->fops->write)
	return -EINVAL;
	if (!media_devnode_is_registered(mdev))
	return -EIO;
	return mdev->fops->write(filp, buf, sz, off);
	}

	static unsigned int media_poll(struct file *filp,
	struct poll_table_struct *poll)
	{
	struct media_devnode *mdev = media_devnode_data(filp);

	if (!media_devnode_is_registered(mdev))
	return POLLERR \| POLLHUP;
	if (!mdev->fops->poll)
	return DEFAULT_POLLMASK;
	return mdev->fops->poll(filp, poll);
	}

	static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
	{
	struct media_devnode *mdev = media_devnode_data(filp);

	if (!mdev->fops->ioctl)
	return -ENOTTY;

	if (!media_devnode_is_registered(mdev))
	return -EIO;

	return mdev->fops->ioctl(filp, cmd, arg);
	}

	/* Override for the open function */
	static int media_open(struct inode inode, struct file filp)
	{
	struct media_devnode *mdev;
	int ret;

	/* Check if the media device is available. This needs to be done with
	* the media_devnode_lock held to prevent an open/unregister race:
	* without the lock, the device could be unregistered and freed between
	* the media_devnode_is_registered() and get_device() calls, leading to
	* a crash.
	*/
	mutex_lock(&media_devnode_lock);
	mdev = container_of(inode->i_cdev, struct media_devnode, cdev);
	/* return ENXIO if the media device has been removed
	already or if it is not registered anymore. */
	if (!media_devnode_is_registered(mdev)) {
	mutex_unlock(&media_devnode_lock);
	return -ENXIO;
	}
	/* and increase the device refcount */
	get_device(&mdev->dev);
	mutex_unlock(&media_devnode_lock);

	filp->private_data = mdev;

	if (mdev->fops->open) {
	ret = mdev->fops->open(filp);
	if (ret) {
	put_device(&mdev->dev);
	return ret;
	}
	}

	return 0;
	}

	/* Override for the release function */
	static int media_release(struct inode inode, struct file filp)
	{
	struct media_devnode *mdev = media_devnode_data(filp);
	int ret = 0;

	if (mdev->fops->release)
	mdev->fops->release(filp);

	/* decrease the refcount unconditionally since the release()
	return value is ignored. */
	put_device(&mdev->dev);
	filp->private_data = NULL;
	return ret;
	}

	static const struct file_operations media_devnode_fops = {
	.owner = THIS_MODULE,
	.read = media_read,
	.write = media_write,
	.open = media_open,
	.unlocked_ioctl = media_ioctl,
	.release = media_release,
	.poll = media_poll,
	.llseek = no_llseek,
	};

	/**
	* media_devnode_register - register a media device node
	* @mdev: media device node structure we want to register
	*
	* The registration code assigns minor numbers and registers the new device node
	* with the kernel. An error is returned if no free minor number can be found,
	* or if the registration of the device node fails.
	*
	* Zero is returned on success.
	*
	* Note that if the media_devnode_register call fails, the release() callback of
	* the media_devnode structure is not called, so the caller is responsible for
	* freeing any data.
	*/
	int __must_check media_devnode_register(struct media_devnode *mdev)
	{
	int minor;
	int ret;

	/* Part 1: Find a free minor number */
	mutex_lock(&media_devnode_lock);
	minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
	if (minor == MEDIA_NUM_DEVICES) {
	mutex_unlock(&media_devnode_lock);
	pr_err("could not get a free minor\n");
	return -ENFILE;
	}

	set_bit(minor, media_devnode_nums);
	mutex_unlock(&media_devnode_lock);

	mdev->minor = minor;

	/* Part 2: Initialize and register the character device */
	cdev_init(&mdev->cdev, &media_devnode_fops);
	mdev->cdev.owner = mdev->fops->owner;

	ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1);
	if (ret < 0) {
	pr_err("%s: cdev_add failed\n", __func__);
	goto error;
	}

	/* Part 3: Register the media device */
	mdev->dev.bus = &media_bus_type;
	mdev->dev.devt = MKDEV(MAJOR(media_dev_t), mdev->minor);
	mdev->dev.release = media_devnode_release;
	if (mdev->parent)
	mdev->dev.parent = mdev->parent;
	dev_set_name(&mdev->dev, "media%d", mdev->minor);
	ret = device_register(&mdev->dev);
	if (ret < 0) {
	pr_err("%s: device_register failed\n", __func__);
	goto error;
	}

	/* Part 4: Activate this minor. The char device can now be used. */
	set_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);

	return 0;

	error:
	cdev_del(&mdev->cdev);
	clear_bit(mdev->minor, media_devnode_nums);
	return ret;
	}

	/**
	* media_devnode_unregister - unregister a media device node
	* @mdev: the device node to unregister
	*
	* This unregisters the passed device. Future open calls will be met with
	* errors.
	*
	* This function can safely be called if the device node has never been
	* registered or has already been unregistered.
	*/
	void media_devnode_unregister(struct media_devnode *mdev)
	{
	/* Check if mdev was ever registered at all */
	if (!media_devnode_is_registered(mdev))
	return;

	mutex_lock(&media_devnode_lock);
	clear_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
	mutex_unlock(&media_devnode_lock);
	device_unregister(&mdev->dev);
	}

	/*
	* Initialise media for linux
	*/
	static int __init media_devnode_init(void)
	{
	int ret;

	pr_info("Linux media interface: v0.10\n");
	ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
	MEDIA_NAME);
	if (ret < 0) {
	pr_warn("unable to allocate major\n");
	return ret;
	}

	ret = bus_register(&media_bus_type);
	if (ret < 0) {
	unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
	pr_warn("bus_register failed\n");
	return -EIO;
	}

	return 0;
	}

	static void __exit media_devnode_exit(void)
	{
	bus_unregister(&media_bus_type);
	unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
	}

	subsys_initcall(media_devnode_init);
	module_exit(media_devnode_exit)

	MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
	MODULE_DESCRIPTION("Device node registration for media drivers");
	MODULE_LICENSE("GPL");