// SPDX-License-Identifier: GPL-2.0-only/* * Media device node * * Copyright (C) 2010 Nokia Corporation * * Based on drivers/media/video/v4l2_dev.c code authored by *	Mauro Carvalho Chehab <mchehab@kernel.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> * * -- * * 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>#include <media/media-device.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 *devnode = to_media_devnode(cd); 	mutex_lock(&media_devnode_lock);	/* Mark device node number as free */	clear_bit(devnode->minor, media_devnode_nums);	mutex_unlock(&media_devnode_lock); 	/* Release media_devnode and perform other cleanups as needed. */	if (devnode->release)		devnode->release(devnode); 	kfree(devnode);	pr_debug("%s: Media Devnode Deallocated\n", __func__);} static const 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 *devnode = media_devnode_data(filp); 	if (!devnode->fops->read)		return -EINVAL;	if (!media_devnode_is_registered(devnode))		return -EIO;	return devnode->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 *devnode = media_devnode_data(filp); 	if (!devnode->fops->write)		return -EINVAL;	if (!media_devnode_is_registered(devnode))		return -EIO;	return devnode->fops->write(filp, buf, sz, off);} static __poll_t media_poll(struct file *filp,			       struct poll_table_struct *poll){	struct media_devnode *devnode = media_devnode_data(filp); 	if (!media_devnode_is_registered(devnode))		return EPOLLERR | EPOLLHUP;	if (!devnode->fops->poll)		return DEFAULT_POLLMASK;	return devnode->fops->poll(filp, poll);} static long__media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg,	      long (*ioctl_func)(struct file *filp, unsigned int cmd,				 unsigned long arg)){	struct media_devnode *devnode = media_devnode_data(filp); 	if (!ioctl_func)		return -ENOTTY; 	if (!media_devnode_is_registered(devnode))		return -EIO; 	return ioctl_func(filp, cmd, arg);} static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg){	struct media_devnode *devnode = media_devnode_data(filp); 	return __media_ioctl(filp, cmd, arg, devnode->fops->ioctl);} #ifdef CONFIG_COMPAT static long media_compat_ioctl(struct file *filp, unsigned int cmd,			       unsigned long arg){	struct media_devnode *devnode = media_devnode_data(filp); 	return __media_ioctl(filp, cmd, arg, devnode->fops->compat_ioctl);} #endif /* CONFIG_COMPAT */ /* Override for the open function */static int media_open(struct inode *inode, struct file *filp){	struct media_devnode *devnode;	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);	devnode = 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(devnode)) {		mutex_unlock(&media_devnode_lock);		return -ENXIO;	}	/* and increase the device refcount */	get_device(&devnode->dev);	mutex_unlock(&media_devnode_lock); 	filp->private_data = devnode; 	if (devnode->fops->open) {		ret = devnode->fops->open(filp);		if (ret) {			put_device(&devnode->dev);			filp->private_data = NULL;			return ret;		}	} 	return 0;} /* Override for the release function */static int media_release(struct inode *inode, struct file *filp){	struct media_devnode *devnode = media_devnode_data(filp); 	if (devnode->fops->release)		devnode->fops->release(filp); 	filp->private_data = NULL; 	/* decrease the refcount unconditionally since the release()	   return value is ignored. */	put_device(&devnode->dev); 	return 0;} static const struct file_operations media_devnode_fops = {	.owner = THIS_MODULE,	.read = media_read,	.write = media_write,	.open = media_open,	.unlocked_ioctl = media_ioctl,#ifdef CONFIG_COMPAT	.compat_ioctl = media_compat_ioctl,#endif /* CONFIG_COMPAT */	.release = media_release,	.poll = media_poll,}; int __must_check media_devnode_register(struct media_device *mdev,					struct media_devnode *devnode,					struct module *owner){	int minor;	int ret; 	/* Part 1: Find a free minor number */	mutex_lock(&media_devnode_lock);	minor = find_first_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES);	if (minor == MEDIA_NUM_DEVICES) {		mutex_unlock(&media_devnode_lock);		pr_err("could not get a free minor\n");		kfree(devnode);		return -ENFILE;	} 	set_bit(minor, media_devnode_nums);	mutex_unlock(&media_devnode_lock); 	devnode->minor = minor;	devnode->media_dev = mdev; 	/* Part 1: Initialize dev now to use dev.kobj for cdev.kobj.parent */	devnode->dev.bus = &media_bus_type;	devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor);	devnode->dev.release = media_devnode_release;	if (devnode->parent)		devnode->dev.parent = devnode->parent;	dev_set_name(&devnode->dev, "media%d", devnode->minor);	device_initialize(&devnode->dev); 	/* Part 2: Initialize the character device */	cdev_init(&devnode->cdev, &media_devnode_fops);	devnode->cdev.owner = owner;	kobject_set_name(&devnode->cdev.kobj, "media%d", devnode->minor); 	/* Part 3: Add the media and char device */	set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);	ret = cdev_device_add(&devnode->cdev, &devnode->dev);	if (ret < 0) {		clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);		pr_err("%s: cdev_device_add failed\n", __func__);		goto cdev_add_error;	} 	return 0; cdev_add_error:	mutex_lock(&media_devnode_lock);	clear_bit(devnode->minor, media_devnode_nums);	devnode->media_dev = NULL;	mutex_unlock(&media_devnode_lock); 	put_device(&devnode->dev);	return ret;} void media_devnode_unregister_prepare(struct media_devnode *devnode){	/* Check if devnode was ever registered at all */	if (!media_devnode_is_registered(devnode))		return; 	mutex_lock(&media_devnode_lock);	clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);	mutex_unlock(&media_devnode_lock);} void media_devnode_unregister(struct media_devnode *devnode){	mutex_lock(&media_devnode_lock);	/* Delete the cdev on this minor as well */	cdev_device_del(&devnode->cdev, &devnode->dev);	devnode->media_dev = NULL;	mutex_unlock(&media_devnode_lock); 	put_device(&devnode->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");