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/* SPDX-License-Identifier: GPL-2.0-only */
* Media device node
* Copyright (C) 2010 Nokia Corporation
* Contacts: Laurent Pinchart <>
* Sakari Ailus <>
* --
* Common functions for media-related drivers to register and unregister media
* device nodes.
#include <linux/poll.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/cdev.h>
struct media_device;
* Flag to mark the media_devnode struct as registered. Drivers must not touch
* this flag directly, it will be set and cleared by media_devnode_register and
* media_devnode_unregister.
* struct media_file_operations - Media device file operations
* @owner: should be filled with %THIS_MODULE
* @read: pointer to the function that implements read() syscall
* @write: pointer to the function that implements write() syscall
* @poll: pointer to the function that implements poll() syscall
* @ioctl: pointer to the function that implements ioctl() syscall
* @compat_ioctl: pointer to the function that will handle 32 bits userspace
* calls to the ioctl() syscall on a Kernel compiled with 64 bits.
* @open: pointer to the function that implements open() syscall
* @release: pointer to the function that will release the resources allocated
* by the @open function.
struct media_file_operations {
struct module *owner;
ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
__poll_t (*poll) (struct file *, struct poll_table_struct *);
long (*ioctl) (struct file *, unsigned int, unsigned long);
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
int (*open) (struct file *);
int (*release) (struct file *);
* struct media_devnode - Media device node
* @media_dev: pointer to struct &media_device
* @fops: pointer to struct &media_file_operations with media device ops
* @dev: pointer to struct &device containing the media controller device
* @cdev: struct cdev pointer character device
* @parent: parent device
* @minor: device node minor number
* @flags: flags, combination of the ``MEDIA_FLAG_*`` constants
* @release: release callback called at the end of ``media_devnode_release()``
* routine at media-device.c.
* This structure represents a media-related device node.
* The @parent is a physical device. It must be set by core or device drivers
* before registering the node.
struct media_devnode {
struct media_device *media_dev;
/* device ops */
const struct media_file_operations *fops;
/* sysfs */
struct device dev; /* media device */
struct cdev cdev; /* character device */
struct device *parent; /* device parent */
/* device info */
int minor;
unsigned long flags; /* Use bitops to access flags */
/* callbacks */
void (*release)(struct media_devnode *devnode);
/* dev to media_devnode */
#define to_media_devnode(cd) container_of(cd, struct media_devnode, dev)
* media_devnode_register - register a media device node
* @mdev: struct media_device we want to register a device node
* @devnode: media device node structure we want to register
* @owner: should be filled with %THIS_MODULE
* 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_device *mdev,
struct media_devnode *devnode,
struct module *owner);
* media_devnode_unregister_prepare - clear the media device node register bit
* @devnode: the device node to prepare for unregister
* This clears the passed device register bit. Future open calls will be met
* with errors. Should be called before media_devnode_unregister() to avoid
* races with unregister and device file open calls.
* This function can safely be called if the device node has never been
* registered or has already been unregistered.
void media_devnode_unregister_prepare(struct media_devnode *devnode);
* media_devnode_unregister - unregister a media device node
* @devnode: the device node to unregister
* This unregisters the passed device. Future open calls will be met with
* errors.
* Should be called after media_devnode_unregister_prepare()
void media_devnode_unregister(struct media_devnode *devnode);
* media_devnode_data - returns a pointer to the &media_devnode
* @filp: pointer to struct &file
static inline struct media_devnode *media_devnode_data(struct file *filp)
return filp->private_data;
* media_devnode_is_registered - returns true if &media_devnode is registered;
* false otherwise.
* @devnode: pointer to struct &media_devnode.
* Note: If mdev is NULL, it also returns false.
static inline int media_devnode_is_registered(struct media_devnode *devnode)
if (!devnode)
return false;
return test_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
#endif /* _MEDIA_DEVNODE_H */