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  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  21  *
  22  * --
  23  *
  24  * Common functions for media-related drivers to register and unregister media
  25  * device nodes.
  26  */
  27
  28 #ifndef _MEDIA_DEVNODE_H
  29 #define _MEDIA_DEVNODE_H
  30
  31 #include <linux/poll.h>
  32 #include <linux/fs.h>
  33 #include <linux/device.h>
  34 #include <linux/cdev.h>
  35
  36 struct media_device;
  37
  38 /*
  39  * Flag to mark the media_devnode struct as registered. Drivers must not touch
  40  * this flag directly, it will be set and cleared by media_devnode_register and
  41  * media_devnode_unregister.
  42  */
  43 #define MEDIA_FLAG_REGISTERED   0
  44
  45 /**
  46  * struct media_file_operations - Media device file operations
  47  *
  48  * @owner: should be filled with %THIS_MODULE
  49  * @read: pointer to the function that implements read() syscall
  50  * @write: pointer to the function that implements write() syscall
  51  * @poll: pointer to the function that implements poll() syscall
  52  * @ioctl: pointer to the function that implements ioctl() syscall
  53  * @compat_ioctl: pointer to the function that will handle 32 bits userspace
  54  *      calls to the the ioctl() syscall on a Kernel compiled with 64 bits.
  55  * @open: pointer to the function that implements open() syscall
  56  * @release: pointer to the function that will release the resources allocated
  57  *      by the @open function.
  58  */
  59 struct media_file_operations {
  60         struct module *owner;
  61         ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
  62         ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
  63         unsigned int (*poll) (struct file *, struct poll_table_struct *);
  64         long (*ioctl) (struct file *, unsigned int, unsigned long);
  65         long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
  66         int (*open) (struct file *);
  67         int (*release) (struct file *);
  68 };
  69
  70 /**
  71  * struct media_devnode - Media device node
  72  * @media_dev:  pointer to struct &media_device
  73  * @fops:       pointer to struct &media_file_operations with media device ops
  74  * @dev:        pointer to struct &device containing the media controller device
  75  * @cdev:       struct cdev pointer character device
  76  * @parent:     parent device
  77  * @minor:      device node minor number
  78  * @flags:      flags, combination of the MEDIA_FLAG_* constants
  79  * @release:    release callback called at the end of media_devnode_release()
  80  *
  81  * This structure represents a media-related device node.
  82  *
  83  * The @parent is a physical device. It must be set by core or device drivers
  84  * before registering the node.
  85  */
  86 struct media_devnode {
  87         struct media_device *media_dev;
  88
  89         /* device ops */
  90         const struct media_file_operations *fops;
  91
  92         /* sysfs */
  93         struct device dev;              /* media device */
  94         struct cdev cdev;               /* character device */
  95         struct device *parent;          /* device parent */
  96
  97         /* device info */
  98         int minor;
  99         unsigned long flags;            /* Use bitops to access flags */
 100
 101         /* callbacks */
 102         void (*release)(struct media_devnode *devnode);
 103 };
 104
 105 /* dev to media_devnode */
 106 #define to_media_devnode(cd) container_of(cd, struct media_devnode, dev)
 107
 108 /**
 109  * media_devnode_register - register a media device node
 110  *
 111  * @mdev: struct media_device we want to register a device node
 112  * @devnode: media device node structure we want to register
 113  * @owner: should be filled with %THIS_MODULE
 114  *
 115  * The registration code assigns minor numbers and registers the new device node
 116  * with the kernel. An error is returned if no free minor number can be found,
 117  * or if the registration of the device node fails.
 118  *
 119  * Zero is returned on success.
 120  *
 121  * Note that if the media_devnode_register call fails, the release() callback of
 122  * the media_devnode structure is *not* called, so the caller is responsible for
 123  * freeing any data.
 124  */
 125 int __must_check media_devnode_register(struct media_device *mdev,
 126                                         struct media_devnode *devnode,
 127                                         struct module *owner);
 128
 129 /**
 130  * media_devnode_unregister_prepare - clear the media device node register bit
 131  * @devnode: the device node to prepare for unregister
 132  *
 133  * This clears the passed device register bit. Future open calls will be met
 134  * with errors. Should be called before media_devnode_unregister() to avoid
 135  * races with unregister and device file open calls.
 136  *
 137  * This function can safely be called if the device node has never been
 138  * registered or has already been unregistered.
 139  */
 140 void media_devnode_unregister_prepare(struct media_devnode *devnode);
 141
 142 /**
 143  * media_devnode_unregister - unregister a media device node
 144  * @devnode: the device node to unregister
 145  *
 146  * This unregisters the passed device. Future open calls will be met with
 147  * errors.
 148  *
 149  * Should be called after media_devnode_unregister_prepare()
 150  */
 151 void media_devnode_unregister(struct media_devnode *devnode);
 152
 153 /**
 154  * media_devnode_data - returns a pointer to the &media_devnode
 155  *
 156  * @filp: pointer to struct &file
 157  */
 158 static inline struct media_devnode *media_devnode_data(struct file *filp)
 159 {
 160         return filp->private_data;
 161 }
 162
 163 /**
 164  * media_devnode_is_registered - returns true if &media_devnode is registered;
 165  *      false otherwise.
 166  *
 167  * @devnode: pointer to struct &media_devnode.
 168  *
 169  * Note: If mdev is NULL, it also returns false.
 170  */
 171 static inline int media_devnode_is_registered(struct media_devnode *devnode)
 172 {
 173         if (!devnode)
 174                 return false;
 175
 176         return test_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
 177 }
 178
 179 #endif /* _MEDIA_DEVNODE_H */