include/media/media-devnode.h

   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  */
 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 */