// 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 (version 2) * Alan Cox, (version 1) * * Contacts: Laurent Pinchart * Sakari Ailus * * -- * * 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 #include #include #include #include #include #include #include #include #include #include #include #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 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); pr_debug("%s: Media Release\n", __func__); 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, .llseek = no_llseek, }; 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 "); MODULE_DESCRIPTION("Device node registration for media drivers"); MODULE_LICENSE("GPL");