v4l2-fh.h

  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 */