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1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * v4l2-fh.h
4 *
5 * V4L2 file handle. Store per file handle data for the V4L2
6 * framework. Using file handles is mandatory for the drivers.
7 *
8 * Copyright (C) 2009--2010 Nokia Corporation.
9 *
10 * Contact: Sakari Ailus <sakari.ailus@iki.fi>
11 */
12
13#ifndef V4L2_FH_H
14#define V4L2_FH_H
15
16#include <linux/fs.h>
17#include <linux/kconfig.h>
18#include <linux/list.h>
19#include <linux/videodev2.h>
20
21struct video_device;
22struct v4l2_ctrl_handler;
23
24/**
25 * struct v4l2_fh - Describes a V4L2 file handler
26 *
27 * @list: list of file handlers
28 * @vdev: pointer to &struct video_device
29 * @ctrl_handler: pointer to &struct v4l2_ctrl_handler
30 * @prio: priority of the file handler, as defined by &enum v4l2_priority
31 *
32 * @wait: event' s wait queue
33 * @subscribe_lock: serialise changes to the subscribed list; guarantee that
34 * the add and del event callbacks are orderly called
35 * @subscribed: list of subscribed events
36 * @available: list of events waiting to be dequeued
37 * @navailable: number of available events at @available list
38 * @sequence: event sequence number
39 *
40 * @m2m_ctx: pointer to &struct v4l2_m2m_ctx
41 */
42struct v4l2_fh {
43 struct list_head list;
44 struct video_device *vdev;
45 struct v4l2_ctrl_handler *ctrl_handler;
46 enum v4l2_priority prio;
47
48 /* Events */
49 wait_queue_head_t wait;
50 struct mutex subscribe_lock;
51 struct list_head subscribed;
52 struct list_head available;
53 unsigned int navailable;
54 u32 sequence;
55
56 struct v4l2_m2m_ctx *m2m_ctx;
57};
58
59/**
60 * file_to_v4l2_fh - Return the v4l2_fh associated with a struct file
61 *
62 * @filp: pointer to &struct file
63 *
64 * This function should be used by drivers to retrieve the &struct v4l2_fh
65 * instance pointer stored in the file private_data instead of accessing the
66 * private_data field directly.
67 */
68static inline struct v4l2_fh *file_to_v4l2_fh(struct file *filp)
69{
70 return filp->private_data;
71}
72
73/**
74 * v4l2_fh_init - Initialise the file handle.
75 *
76 * @fh: pointer to &struct v4l2_fh
77 * @vdev: pointer to &struct video_device
78 *
79 * Parts of the V4L2 framework using the
80 * file handles should be initialised in this function. Must be called
81 * from driver's v4l2_file_operations->open\(\) handler if the driver
82 * uses &struct v4l2_fh.
83 */
84void v4l2_fh_init(struct v4l2_fh *fh, struct video_device *vdev);
85
86/**
87 * v4l2_fh_add - Add the fh to the list of file handles on a video_device.
88 *
89 * @fh: pointer to &struct v4l2_fh
90 * @filp: pointer to &struct file associated with @fh
91 *
92 * The function sets filp->private_data to point to @fh.
93 *
94 * .. note::
95 * The @fh file handle must be initialised first.
96 */
97void v4l2_fh_add(struct v4l2_fh *fh, struct file *filp);
98
99/**
100 * v4l2_fh_open - Ancillary routine that can be used as the open\(\) op
101 * of v4l2_file_operations.
102 *
103 * @filp: pointer to struct file
104 *
105 * It allocates a v4l2_fh and inits and adds it to the &struct video_device
106 * associated with the file pointer.
107 *
108 * On error filp->private_data will be %NULL, otherwise it will point to
109 * the &struct v4l2_fh.
110 */
111int v4l2_fh_open(struct file *filp);
112
113/**
114 * v4l2_fh_del - Remove file handle from the list of file handles.
115 *
116 * @fh: pointer to &struct v4l2_fh
117 * @filp: pointer to &struct file associated with @fh
118 *
119 * The function resets filp->private_data to NULL.
120 *
121 * .. note::
122 * Must be called in v4l2_file_operations->release\(\) handler if the driver
123 * uses &struct v4l2_fh.
124 */
125void v4l2_fh_del(struct v4l2_fh *fh, struct file *filp);
126
127/**
128 * v4l2_fh_exit - Release resources related to a file handle.
129 *
130 * @fh: pointer to &struct v4l2_fh
131 *
132 * Parts of the V4L2 framework using the v4l2_fh must release their
133 * resources here, too.
134 *
135 * .. note::
136 * Must be called in v4l2_file_operations->release\(\) handler if the
137 * driver uses &struct v4l2_fh.
138 */
139void v4l2_fh_exit(struct v4l2_fh *fh);
140
141/**
142 * v4l2_fh_release - Ancillary routine that can be used as the release\(\) op
143 * of v4l2_file_operations.
144 *
145 * @filp: pointer to struct file
146 *
147 * It deletes and exits the v4l2_fh associated with the file pointer and
148 * frees it. It will do nothing if filp->private_data (the pointer to the
149 * v4l2_fh struct) is %NULL.
150 *
151 * This function always returns 0.
152 */
153int v4l2_fh_release(struct file *filp);
154
155/**
156 * v4l2_fh_is_singular - Returns 1 if this filehandle is the only filehandle
157 * opened for the associated video_device.
158 *
159 * @fh: pointer to &struct v4l2_fh
160 *
161 * If @fh is NULL, then it returns 0.
162 */
163int v4l2_fh_is_singular(struct v4l2_fh *fh);
164
165/**
166 * v4l2_fh_is_singular_file - Returns 1 if this filehandle is the only
167 * filehandle opened for the associated video_device.
168 *
169 * @filp: pointer to struct file
170 *
171 * This is a helper function variant of v4l2_fh_is_singular() with uses
172 * struct file as argument.
173 *
174 * If filp->private_data is %NULL, then it will return 0.
175 */
176static inline int v4l2_fh_is_singular_file(struct file *filp)
177{
178 return v4l2_fh_is_singular(filp->private_data);
179}
180
181#endif /* V4L2_EVENT_H */