/* * 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");