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 /*
  37  * Flag to mark the media_devnode struct as registered. Drivers must not touch
  38  * this flag directly, it will be set and cleared by media_devnode_register and
  39  * media_devnode_unregister.
  40  */
  41 #define MEDIA_FLAG_REGISTERED   0
  42
  43 /**
  44  * struct media_file_operations - Media device file operations
  45  *
  46  * @owner: should be filled with %THIS_MODULE
  47  * @read: pointer to the function that implements read() syscall
  48  * @write: pointer to the function that implements write() syscall
  49  * @poll: pointer to the function that implements poll() syscall
  50  * @ioctl: pointer to the function that implements ioctl() syscall
  51  * @compat_ioctl: pointer to the function that will handle 32 bits userspace
  52  *      calls to the the ioctl() syscall on a Kernel compiled with 64 bits.
  53  * @open: pointer to the function that implements open() syscall
  54  * @release: pointer to the function that will release the resources allocated
  55  *      by the @open function.
  56  */
  57 struct media_file_operations {
  58         struct module *owner;
  59         ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
  60         ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
  61         unsigned int (*poll) (struct file *, struct poll_table_struct *);
  62         long (*ioctl) (struct file *, unsigned int, unsigned long);
  63         long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
  64         int (*open) (struct file *);
  65         int (*release) (struct file *);
  66 };
  67
  68 /**
  69  * struct media_devnode - Media device node
  70  * @fops:       pointer to struct &media_file_operations with media device ops
  71  * @dev:        struct device pointer for the media controller device
  72  * @cdev:       struct cdev pointer character device
  73  * @parent:     parent device
  74  * @minor:      device node minor number
  75  * @flags:      flags, combination of the MEDIA_FLAG_* constants
  76  * @release:    release callback called at the end of media_devnode_release()
  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         /* device ops */
  85         const struct media_file_operations *fops;
  86
  87         /* sysfs */
  88         struct device dev;              /* media device */
  89         struct cdev cdev;               /* character device */
  90         struct device *parent;          /* device parent */
  91
  92         /* device info */
  93         int minor;
  94         unsigned long flags;            /* Use bitops to access flags */
  95
  96         /* callbacks */
  97         void (*release)(struct media_devnode *mdev);
  98 };
  99
 100 /* dev to media_devnode */
 101 #define to_media_devnode(cd) container_of(cd, struct media_devnode, dev)
 102
 103 /**
 104  * media_devnode_register - register a media device node
 105  *
 106  * @mdev: media device node structure we want to register
 107  * @owner: should be filled with %THIS_MODULE
 108  *
 109  * The registration code assigns minor numbers and registers the new device node
 110  * with the kernel. An error is returned if no free minor number can be found,
 111  * or if the registration of the device node fails.
 112  *
 113  * Zero is returned on success.
 114  *
 115  * Note that if the media_devnode_register call fails, the release() callback of
 116  * the media_devnode structure is *not* called, so the caller is responsible for
 117  * freeing any data.
 118  */
 119 int __must_check media_devnode_register(struct media_devnode *mdev,
 120                                         struct module *owner);
 121
 122 /**
 123  * media_devnode_unregister - unregister a media device node
 124  * @mdev: the device node to unregister
 125  *
 126  * This unregisters the passed device. Future open calls will be met with
 127  * errors.
 128  *
 129  * This function can safely be called if the device node has never been
 130  * registered or has already been unregistered.
 131  */
 132 void media_devnode_unregister(struct media_devnode *mdev);
 133
 134 /**
 135  * media_devnode_data - returns a pointer to the &media_devnode
 136  *
 137  * @filp: pointer to struct &file
 138  */
 139 static inline struct media_devnode *media_devnode_data(struct file *filp)
 140 {
 141         return filp->private_data;
 142 }
 143
 144 /**
 145  * media_devnode_is_registered - returns true if &media_devnode is registered;
 146  *      false otherwise.
 147  *
 148  * @mdev: pointer to struct &media_devnode.
 149  */
 150 static inline int media_devnode_is_registered(struct media_devnode *mdev)
 151 {
 152         return test_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
 153 }
 154
 155 #endif /* _MEDIA_DEVNODE_H */