include/media/media-devnode.h

   1 /*
   2  * Media device node
   3  *
   4  * Copyright (C) 2010 Nokia Corporation
   5  *
   6  * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
   7  *           Sakari Ailus <sakari.ailus@iki.fi>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * --
  19  *
  20  * Common functions for media-related drivers to register and unregister media
  21  * device nodes.
  22  */
  23
  24 #ifndef _MEDIA_DEVNODE_H
  25 #define _MEDIA_DEVNODE_H
  26
  27 #include <linux/poll.h>
  28 #include <linux/fs.h>
  29 #include <linux/device.h>
  30 #include <linux/cdev.h>
  31
  32 struct media_device;
  33
  34 /*
  35  * Flag to mark the media_devnode struct as registered. Drivers must not touch
  36  * this flag directly, it will be set and cleared by media_devnode_register and
  37  * media_devnode_unregister.
  38  */
  39 #define MEDIA_FLAG_REGISTERED   0
  40
  41 /**
  42  * struct media_file_operations - Media device file operations
  43  *
  44  * @owner: should be filled with %THIS_MODULE
  45  * @read: pointer to the function that implements read() syscall
  46  * @write: pointer to the function that implements write() syscall
  47  * @poll: pointer to the function that implements poll() syscall
  48  * @ioctl: pointer to the function that implements ioctl() syscall
  49  * @compat_ioctl: pointer to the function that will handle 32 bits userspace
  50  *      calls to the the ioctl() syscall on a Kernel compiled with 64 bits.
  51  * @open: pointer to the function that implements open() syscall
  52  * @release: pointer to the function that will release the resources allocated
  53  *      by the @open function.
  54  */
  55 struct media_file_operations {
  56         struct module *owner;
  57         ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
  58         ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
  59         __poll_t (*poll) (struct file *, struct poll_table_struct *);
  60         long (*ioctl) (struct file *, unsigned int, unsigned long);
  61         long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
  62         int (*open) (struct file *);
  63         int (*release) (struct file *);
  64 };
  65
  66 /**
  67  * struct media_devnode - Media device node
  68  * @media_dev:  pointer to struct &media_device
  69  * @fops:       pointer to struct &media_file_operations with media device ops
  70  * @dev:        pointer to struct &device containing the media controller device
  71  * @cdev:       struct cdev pointer character device
  72  * @parent:     parent device
  73  * @minor:      device node minor number
  74  * @flags:      flags, combination of the ``MEDIA_FLAG_*`` constants
  75  * @release:    release callback called at the end of ``media_devnode_release()``
  76  *              routine at media-device.c.
  77  *
  78  * This structure represents a media-related device node.
  79  *
  80  * The @parent is a physical device. It must be set by core or device drivers
  81  * before registering the node.
  82  */
  83 struct media_devnode {
  84         struct media_device *media_dev;
  85
  86         /* device ops */
  87         const struct media_file_operations *fops;
  88
  89         /* sysfs */
  90         struct device dev;              /* media device */
  91         struct cdev cdev;               /* character device */
  92         struct device *parent;          /* device parent */
  93
  94         /* device info */
  95         int minor;
  96         unsigned long flags;            /* Use bitops to access flags */
  97
  98         /* callbacks */
  99         void (*release)(struct media_devnode *devnode);
 100 };
 101
 102 /* dev to media_devnode */
 103 #define to_media_devnode(cd) container_of(cd, struct media_devnode, dev)
 104
 105 /**
 106  * media_devnode_register - register a media device node
 107  *
 108  * @mdev: struct media_device we want to register a device node
 109  * @devnode: media device node structure we want to register
 110  * @owner: should be filled with %THIS_MODULE
 111  *
 112  * The registration code assigns minor numbers and registers the new device node
 113  * with the kernel. An error is returned if no free minor number can be found,
 114  * or if the registration of the device node fails.
 115  *
 116  * Zero is returned on success.
 117  *
 118  * Note that if the media_devnode_register call fails, the release() callback of
 119  * the media_devnode structure is *not* called, so the caller is responsible for
 120  * freeing any data.
 121  */
 122 int __must_check media_devnode_register(struct media_device *mdev,
 123                                         struct media_devnode *devnode,
 124                                         struct module *owner);
 125
 126 /**
 127  * media_devnode_unregister_prepare - clear the media device node register bit
 128  * @devnode: the device node to prepare for unregister
 129  *
 130  * This clears the passed device register bit. Future open calls will be met
 131  * with errors. Should be called before media_devnode_unregister() to avoid
 132  * races with unregister and device file open calls.
 133  *
 134  * This function can safely be called if the device node has never been
 135  * registered or has already been unregistered.
 136  */
 137 void media_devnode_unregister_prepare(struct media_devnode *devnode);
 138
 139 /**
 140  * media_devnode_unregister - unregister a media device node
 141  * @devnode: the device node to unregister
 142  *
 143  * This unregisters the passed device. Future open calls will be met with
 144  * errors.
 145  *
 146  * Should be called after media_devnode_unregister_prepare()
 147  */
 148 void media_devnode_unregister(struct media_devnode *devnode);
 149
 150 /**
 151  * media_devnode_data - returns a pointer to the &media_devnode
 152  *
 153  * @filp: pointer to struct &file
 154  */
 155 static inline struct media_devnode *media_devnode_data(struct file *filp)
 156 {
 157         return filp->private_data;
 158 }
 159
 160 /**
 161  * media_devnode_is_registered - returns true if &media_devnode is registered;
 162  *      false otherwise.
 163  *
 164  * @devnode: pointer to struct &media_devnode.
 165  *
 166  * Note: If mdev is NULL, it also returns false.
 167  */
 168 static inline int media_devnode_is_registered(struct media_devnode *devnode)
 169 {
 170         if (!devnode)
 171                 return false;
 172
 173         return test_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
 174 }
 175
 176 #endif /* _MEDIA_DEVNODE_H */