1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * Media device node
4 *
5 * Copyright (C) 2010 Nokia Corporation
6 *
7 * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
8 * Sakari Ailus <sakari.ailus@iki.fi>
9 *
10 * --
11 *
12 * Common functions for media-related drivers to register and unregister media
13 * device nodes.
14 */
15
16 #ifndef _MEDIA_DEVNODE_H
17 #define _MEDIA_DEVNODE_H
18
19 #include <linux/poll.h>
20 #include <linux/fs.h>
21 #include <linux/device.h>
22 #include <linux/cdev.h>
23
24 struct media_device;
25
26 /*
27 * Flag to mark the media_devnode struct as registered. Drivers must not touch
28 * this flag directly, it will be set and cleared by media_devnode_register and
29 * media_devnode_unregister.
30 */
31 #define MEDIA_FLAG_REGISTERED 0
32
33 /**
34 * struct media_file_operations - Media device file operations
35 *
36 * @owner: should be filled with %THIS_MODULE
37 * @read: pointer to the function that implements read() syscall
38 * @write: pointer to the function that implements write() syscall
39 * @poll: pointer to the function that implements poll() syscall
40 * @ioctl: pointer to the function that implements ioctl() syscall
41 * @compat_ioctl: pointer to the function that will handle 32 bits userspace
42 * calls to the the ioctl() syscall on a Kernel compiled with 64 bits.
43 * @open: pointer to the function that implements open() syscall
44 * @release: pointer to the function that will release the resources allocated
45 * by the @open function.
46 */
47 struct media_file_operations {
48 struct module *owner;
49 ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
50 ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
51 __poll_t (*poll) (struct file *, struct poll_table_struct *);
52 long (*ioctl) (struct file *, unsigned int, unsigned long);
53 long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
54 int (*open) (struct file *);
55 int (*release) (struct file *);
56 };
57
58 /**
59 * struct media_devnode - Media device node
60 * @media_dev: pointer to struct &media_device
61 * @fops: pointer to struct &media_file_operations with media device ops
62 * @dev: pointer to struct &device containing the media controller device
63 * @cdev: struct cdev pointer character device
64 * @parent: parent device
65 * @minor: device node minor number
66 * @flags: flags, combination of the ``MEDIA_FLAG_*`` constants
67 * @release: release callback called at the end of ``media_devnode_release()``
68 * routine at media-device.c.
69 *
70 * This structure represents a media-related device node.
71 *
72 * The @parent is a physical device. It must be set by core or device drivers
73 * before registering the node.
74 */
75 struct media_devnode {
76 struct media_device *media_dev;
77
78 /* device ops */
79 const struct media_file_operations *fops;
80
81 /* sysfs */
82 struct device dev; /* media device */
83 struct cdev cdev; /* character device */
84 struct device *parent; /* device parent */
85
86 /* device info */
87 int minor;
88 unsigned long flags; /* Use bitops to access flags */
89
90 /* callbacks */
91 void (*release)(struct media_devnode *devnode);
92 };
93
94 /* dev to media_devnode */
95 #define to_media_devnode(cd) container_of(cd, struct media_devnode, dev)
96
97 /**
98 * media_devnode_register - register a media device node
99 *
100 * @mdev: struct media_device we want to register a device node
101 * @devnode: media device node structure we want to register
102 * @owner: should be filled with %THIS_MODULE
103 *
104 * The registration code assigns minor numbers and registers the new device node
105 * with the kernel. An error is returned if no free minor number can be found,
106 * or if the registration of the device node fails.
107 *
108 * Zero is returned on success.
109 *
110 * Note that if the media_devnode_register call fails, the release() callback of
111 * the media_devnode structure is *not* called, so the caller is responsible for
112 * freeing any data.
113 */
114 int __must_check media_devnode_register(struct media_device *mdev,
115 struct media_devnode *devnode,
116 struct module *owner);
117
118 /**
119 * media_devnode_unregister_prepare - clear the media device node register bit
120 * @devnode: the device node to prepare for unregister
121 *
122 * This clears the passed device register bit. Future open calls will be met
123 * with errors. Should be called before media_devnode_unregister() to avoid
124 * races with unregister and device file open calls.
125 *
126 * This function can safely be called if the device node has never been
127 * registered or has already been unregistered.
128 */
129 void media_devnode_unregister_prepare(struct media_devnode *devnode);
130
131 /**
132 * media_devnode_unregister - unregister a media device node
133 * @devnode: the device node to unregister
134 *
135 * This unregisters the passed device. Future open calls will be met with
136 * errors.
137 *
138 * Should be called after media_devnode_unregister_prepare()
139 */
140 void media_devnode_unregister(struct media_devnode *devnode);
141
142 /**
143 * media_devnode_data - returns a pointer to the &media_devnode
144 *
145 * @filp: pointer to struct &file
146 */
147 static inline struct media_devnode *media_devnode_data(struct file *filp)
148 {
149 return filp->private_data;
150 }
151
152 /**
153 * media_devnode_is_registered - returns true if &media_devnode is registered;
154 * false otherwise.
155 *
156 * @devnode: pointer to struct &media_devnode.
157 *
158 * Note: If mdev is NULL, it also returns false.
159 */
160 static inline int media_devnode_is_registered(struct media_devnode *devnode)
161 {
162 if (!devnode)
163 return false;
164
165 return test_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
166 }
167
168 #endif /* _MEDIA_DEVNODE_H */