// 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 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_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");
                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 */
        ret = cdev_device_add(&devnode->cdev, &devnode->dev);
        if (ret < 0) {
                pr_err("%s: cdev_device_add failed\n", __func__);
                goto cdev_add_error;
        }

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

        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");