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 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  */
media_devnode_data(struct file * filp)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  */
media_devnode_is_registered(struct media_devnode * devnode)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 */
169