1 /*
2  * v4l2-fh.h
3  *
4  * V4L2 file handle. Store per file handle data for the V4L2
5  * framework. Using file handles is optional for the drivers.
6  *
7  * Copyright (C) 2009--2010 Nokia Corporation.
8  *
9  * Contact: Sakari Ailus <sakari.ailus@iki.fi>
10  *
11  * This program is free software; you can redistribute it and/or
12  * modify it under the terms of the GNU General Public License
13  * version 2 as published by the Free Software Foundation.
14  *
15  * This program is distributed in the hope that it will be useful, but
16  * WITHOUT ANY WARRANTY; without even the implied warranty of
17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
18  * General Public License for more details.
19  */
20 
21 #ifndef V4L2_FH_H
22 #define V4L2_FH_H
23 
24 #include <linux/fs.h>
25 #include <linux/kconfig.h>
26 #include <linux/list.h>
27 #include <linux/videodev2.h>
28 
29 struct video_device;
30 struct v4l2_ctrl_handler;
31 
32 /**
33  * struct v4l2_fh - Describes a V4L2 file handler
34  *
35  * @list: list of file handlers
36  * @vdev: pointer to &struct video_device
37  * @ctrl_handler: pointer to &struct v4l2_ctrl_handler
38  * @prio: priority of the file handler, as defined by &enum v4l2_priority
39  *
40  * @wait: event' s wait queue
41  * @subscribe_lock: serialise changes to the subscribed list; guarantee that
42  *		    the add and del event callbacks are orderly called
43  * @subscribed: list of subscribed events
44  * @available: list of events waiting to be dequeued
45  * @navailable: number of available events at @available list
46  * @sequence: event sequence number
47  *
48  * @m2m_ctx: pointer to &struct v4l2_m2m_ctx
49  */
50 struct v4l2_fh {
51 	struct list_head	list;
52 	struct video_device	*vdev;
53 	struct v4l2_ctrl_handler *ctrl_handler;
54 	enum v4l2_priority	prio;
55 
56 	/* Events */
57 	wait_queue_head_t	wait;
58 	struct mutex		subscribe_lock;
59 	struct list_head	subscribed;
60 	struct list_head	available;
61 	unsigned int		navailable;
62 	u32			sequence;
63 
64 #if IS_ENABLED(CONFIG_V4L2_MEM2MEM_DEV)
65 	struct v4l2_m2m_ctx	*m2m_ctx;
66 #endif
67 };
68 
69 /**
70  * v4l2_fh_init - Initialise the file handle.
71  *
72  * @fh: pointer to &struct v4l2_fh
73  * @vdev: pointer to &struct video_device
74  *
75  * Parts of the V4L2 framework using the
76  * file handles should be initialised in this function. Must be called
77  * from driver's v4l2_file_operations->open\(\) handler if the driver
78  * uses &struct v4l2_fh.
79  */
80 void v4l2_fh_init(struct v4l2_fh *fh, struct video_device *vdev);
81 
82 /**
83  * v4l2_fh_add - Add the fh to the list of file handles on a video_device.
84  *
85  * @fh: pointer to &struct v4l2_fh
86  *
87  * .. note::
88  *    The @fh file handle must be initialised first.
89  */
90 void v4l2_fh_add(struct v4l2_fh *fh);
91 
92 /**
93  * v4l2_fh_open - Ancillary routine that can be used as the open\(\) op
94  *	of v4l2_file_operations.
95  *
96  * @filp: pointer to struct file
97  *
98  * It allocates a v4l2_fh and inits and adds it to the &struct video_device
99  * associated with the file pointer.
100  */
101 int v4l2_fh_open(struct file *filp);
102 
103 /**
104  * v4l2_fh_del - Remove file handle from the list of file handles.
105  *
106  * @fh: pointer to &struct v4l2_fh
107  *
108  * On error filp->private_data will be %NULL, otherwise it will point to
109  * the &struct v4l2_fh.
110  *
111  * .. note::
112  *    Must be called in v4l2_file_operations->release\(\) handler if the driver
113  *    uses &struct v4l2_fh.
114  */
115 void v4l2_fh_del(struct v4l2_fh *fh);
116 
117 /**
118  * v4l2_fh_exit - Release resources related to a file handle.
119  *
120  * @fh: pointer to &struct v4l2_fh
121  *
122  * Parts of the V4L2 framework using the v4l2_fh must release their
123  * resources here, too.
124  *
125  * .. note::
126  *    Must be called in v4l2_file_operations->release\(\) handler if the
127  *    driver uses &struct v4l2_fh.
128  */
129 void v4l2_fh_exit(struct v4l2_fh *fh);
130 
131 /**
132  * v4l2_fh_release - Ancillary routine that can be used as the release\(\) op
133  *	of v4l2_file_operations.
134  *
135  * @filp: pointer to struct file
136  *
137  * It deletes and exits the v4l2_fh associated with the file pointer and
138  * frees it. It will do nothing if filp->private_data (the pointer to the
139  * v4l2_fh struct) is %NULL.
140  *
141  * This function always returns 0.
142  */
143 int v4l2_fh_release(struct file *filp);
144 
145 /**
146  * v4l2_fh_is_singular - Returns 1 if this filehandle is the only filehandle
147  *	 opened for the associated video_device.
148  *
149  * @fh: pointer to &struct v4l2_fh
150  *
151  * If @fh is NULL, then it returns 0.
152  */
153 int v4l2_fh_is_singular(struct v4l2_fh *fh);
154 
155 /**
156  * v4l2_fh_is_singular_file - Returns 1 if this filehandle is the only
157  *	filehandle opened for the associated video_device.
158  *
159  * @filp: pointer to struct file
160  *
161  * This is a helper function variant of v4l2_fh_is_singular() with uses
162  * struct file as argument.
163  *
164  * If filp->private_data is %NULL, then it will return 0.
165  */
v4l2_fh_is_singular_file(struct file * filp)166 static inline int v4l2_fh_is_singular_file(struct file *filp)
167 {
168 	return v4l2_fh_is_singular(filp->private_data);
169 }
170 
171 #endif /* V4L2_EVENT_H */
172