drivers/media/media-devnode.c

   1 /*
   2  * Media device node
   3  *
   4  * Copyright (C) 2010 Nokia Corporation
   5  *
   6  * Based on drivers/media/video/v4l2_dev.c code authored by
   7  *      Mauro Carvalho Chehab <mchehab@kernel.org> (version 2)
   8  *      Alan Cox, <alan@lxorguk.ukuu.org.uk> (version 1)
   9  *
  10  * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
  11  *           Sakari Ailus <sakari.ailus@iki.fi>
  12  *
  13  * This program is free software; you can redistribute it and/or modify
  14  * it under the terms of the GNU General Public License version 2 as
  15  * published by the Free Software Foundation.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * --
  23  *
  24  * Generic media device node infrastructure to register and unregister
  25  * character devices using a dynamic major number and proper reference
  26  * counting.
  27  */
  28
  29 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  30
  31 #include <linux/errno.h>
  32 #include <linux/init.h>
  33 #include <linux/module.h>
  34 #include <linux/kernel.h>
  35 #include <linux/kmod.h>
  36 #include <linux/slab.h>
  37 #include <linux/mm.h>
  38 #include <linux/string.h>
  39 #include <linux/types.h>
  40 #include <linux/uaccess.h>
  41
  42 #include <media/media-devnode.h>
  43 #include <media/media-device.h>
  44
  45 #define MEDIA_NUM_DEVICES       256
  46 #define MEDIA_NAME              "media"
  47
  48 static dev_t media_dev_t;
  49
  50 /*
  51  *      Active devices
  52  */
  53 static DEFINE_MUTEX(media_devnode_lock);
  54 static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
  55
  56 /* Called when the last user of the media device exits. */
  57 static void media_devnode_release(struct device *cd)
  58 {
  59         struct media_devnode *devnode = to_media_devnode(cd);
  60
  61         mutex_lock(&media_devnode_lock);
  62         /* Mark device node number as free */
  63         clear_bit(devnode->minor, media_devnode_nums);
  64         mutex_unlock(&media_devnode_lock);
  65
  66         /* Release media_devnode and perform other cleanups as needed. */
  67         if (devnode->release)
  68                 devnode->release(devnode);
  69
  70         kfree(devnode);
  71         pr_debug("%s: Media Devnode Deallocated\n", __func__);
  72 }
  73
  74 static struct bus_type media_bus_type = {
  75         .name = MEDIA_NAME,
  76 };
  77
  78 static ssize_t media_read(struct file *filp, char __user *buf,
  79                 size_t sz, loff_t *off)
  80 {
  81         struct media_devnode *devnode = media_devnode_data(filp);
  82
  83         if (!devnode->fops->read)
  84                 return -EINVAL;
  85         if (!media_devnode_is_registered(devnode))
  86                 return -EIO;
  87         return devnode->fops->read(filp, buf, sz, off);
  88 }
  89
  90 static ssize_t media_write(struct file *filp, const char __user *buf,
  91                 size_t sz, loff_t *off)
  92 {
  93         struct media_devnode *devnode = media_devnode_data(filp);
  94
  95         if (!devnode->fops->write)
  96                 return -EINVAL;
  97         if (!media_devnode_is_registered(devnode))
  98                 return -EIO;
  99         return devnode->fops->write(filp, buf, sz, off);
 100 }
 101
 102 static __poll_t media_poll(struct file *filp,
 103                                struct poll_table_struct *poll)
 104 {
 105         struct media_devnode *devnode = media_devnode_data(filp);
 106
 107         if (!media_devnode_is_registered(devnode))
 108                 return EPOLLERR | EPOLLHUP;
 109         if (!devnode->fops->poll)
 110                 return DEFAULT_POLLMASK;
 111         return devnode->fops->poll(filp, poll);
 112 }
 113
 114 static long
 115 __media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg,
 116               long (*ioctl_func)(struct file *filp, unsigned int cmd,
 117                                  unsigned long arg))
 118 {
 119         struct media_devnode *devnode = media_devnode_data(filp);
 120
 121         if (!ioctl_func)
 122                 return -ENOTTY;
 123
 124         if (!media_devnode_is_registered(devnode))
 125                 return -EIO;
 126
 127         return ioctl_func(filp, cmd, arg);
 128 }
 129
 130 static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 131 {
 132         struct media_devnode *devnode = media_devnode_data(filp);
 133
 134         return __media_ioctl(filp, cmd, arg, devnode->fops->ioctl);
 135 }
 136
 137 #ifdef CONFIG_COMPAT
 138
 139 static long media_compat_ioctl(struct file *filp, unsigned int cmd,
 140                                unsigned long arg)
 141 {
 142         struct media_devnode *devnode = media_devnode_data(filp);
 143
 144         return __media_ioctl(filp, cmd, arg, devnode->fops->compat_ioctl);
 145 }
 146
 147 #endif /* CONFIG_COMPAT */
 148
 149 /* Override for the open function */
 150 static int media_open(struct inode *inode, struct file *filp)
 151 {
 152         struct media_devnode *devnode;
 153         int ret;
 154
 155         /* Check if the media device is available. This needs to be done with
 156          * the media_devnode_lock held to prevent an open/unregister race:
 157          * without the lock, the device could be unregistered and freed between
 158          * the media_devnode_is_registered() and get_device() calls, leading to
 159          * a crash.
 160          */
 161         mutex_lock(&media_devnode_lock);
 162         devnode = container_of(inode->i_cdev, struct media_devnode, cdev);
 163         /* return ENXIO if the media device has been removed
 164            already or if it is not registered anymore. */
 165         if (!media_devnode_is_registered(devnode)) {
 166                 mutex_unlock(&media_devnode_lock);
 167                 return -ENXIO;
 168         }
 169         /* and increase the device refcount */
 170         get_device(&devnode->dev);
 171         mutex_unlock(&media_devnode_lock);
 172
 173         filp->private_data = devnode;
 174
 175         if (devnode->fops->open) {
 176                 ret = devnode->fops->open(filp);
 177                 if (ret) {
 178                         put_device(&devnode->dev);
 179                         filp->private_data = NULL;
 180                         return ret;
 181                 }
 182         }
 183
 184         return 0;
 185 }
 186
 187 /* Override for the release function */
 188 static int media_release(struct inode *inode, struct file *filp)
 189 {
 190         struct media_devnode *devnode = media_devnode_data(filp);
 191
 192         if (devnode->fops->release)
 193                 devnode->fops->release(filp);
 194
 195         filp->private_data = NULL;
 196
 197         /* decrease the refcount unconditionally since the release()
 198            return value is ignored. */
 199         put_device(&devnode->dev);
 200
 201         pr_debug("%s: Media Release\n", __func__);
 202         return 0;
 203 }
 204
 205 static const struct file_operations media_devnode_fops = {
 206         .owner = THIS_MODULE,
 207         .read = media_read,
 208         .write = media_write,
 209         .open = media_open,
 210         .unlocked_ioctl = media_ioctl,
 211 #ifdef CONFIG_COMPAT
 212         .compat_ioctl = media_compat_ioctl,
 213 #endif /* CONFIG_COMPAT */
 214         .release = media_release,
 215         .poll = media_poll,
 216         .llseek = no_llseek,
 217 };
 218
 219 int __must_check media_devnode_register(struct media_device *mdev,
 220                                         struct media_devnode *devnode,
 221                                         struct module *owner)
 222 {
 223         int minor;
 224         int ret;
 225
 226         /* Part 1: Find a free minor number */
 227         mutex_lock(&media_devnode_lock);
 228         minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
 229         if (minor == MEDIA_NUM_DEVICES) {
 230                 mutex_unlock(&media_devnode_lock);
 231                 pr_err("could not get a free minor\n");
 232                 kfree(devnode);
 233                 return -ENFILE;
 234         }
 235
 236         set_bit(minor, media_devnode_nums);
 237         mutex_unlock(&media_devnode_lock);
 238
 239         devnode->minor = minor;
 240         devnode->media_dev = mdev;
 241
 242         /* Part 1: Initialize dev now to use dev.kobj for cdev.kobj.parent */
 243         devnode->dev.bus = &media_bus_type;
 244         devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor);
 245         devnode->dev.release = media_devnode_release;
 246         if (devnode->parent)
 247                 devnode->dev.parent = devnode->parent;
 248         dev_set_name(&devnode->dev, "media%d", devnode->minor);
 249         device_initialize(&devnode->dev);
 250
 251         /* Part 2: Initialize the character device */
 252         cdev_init(&devnode->cdev, &media_devnode_fops);
 253         devnode->cdev.owner = owner;
 254
 255         /* Part 3: Add the media and char device */
 256         ret = cdev_device_add(&devnode->cdev, &devnode->dev);
 257         if (ret < 0) {
 258                 pr_err("%s: cdev_device_add failed\n", __func__);
 259                 goto cdev_add_error;
 260         }
 261
 262         /* Part 4: Activate this minor. The char device can now be used. */
 263         set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
 264
 265         return 0;
 266
 267 cdev_add_error:
 268         mutex_lock(&media_devnode_lock);
 269         clear_bit(devnode->minor, media_devnode_nums);
 270         devnode->media_dev = NULL;
 271         mutex_unlock(&media_devnode_lock);
 272
 273         put_device(&devnode->dev);
 274         return ret;
 275 }
 276
 277 void media_devnode_unregister_prepare(struct media_devnode *devnode)
 278 {
 279         /* Check if devnode was ever registered at all */
 280         if (!media_devnode_is_registered(devnode))
 281                 return;
 282
 283         mutex_lock(&media_devnode_lock);
 284         clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
 285         mutex_unlock(&media_devnode_lock);
 286 }
 287
 288 void media_devnode_unregister(struct media_devnode *devnode)
 289 {
 290         mutex_lock(&media_devnode_lock);
 291         /* Delete the cdev on this minor as well */
 292         cdev_device_del(&devnode->cdev, &devnode->dev);
 293         mutex_unlock(&media_devnode_lock);
 294         devnode->media_dev = NULL;
 295         put_device(&devnode->dev);
 296 }
 297
 298 /*
 299  *      Initialise media for linux
 300  */
 301 static int __init media_devnode_init(void)
 302 {
 303         int ret;
 304
 305         pr_info("Linux media interface: v0.10\n");
 306         ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
 307                                   MEDIA_NAME);
 308         if (ret < 0) {
 309                 pr_warn("unable to allocate major\n");
 310                 return ret;
 311         }
 312
 313         ret = bus_register(&media_bus_type);
 314         if (ret < 0) {
 315                 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
 316                 pr_warn("bus_register failed\n");
 317                 return -EIO;
 318         }
 319
 320         return 0;
 321 }
 322
 323 static void __exit media_devnode_exit(void)
 324 {
 325         bus_unregister(&media_bus_type);
 326         unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
 327 }
 328
 329 subsys_initcall(media_devnode_init);
 330 module_exit(media_devnode_exit)
 331
 332 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
 333 MODULE_DESCRIPTION("Device node registration for media drivers");
 334 MODULE_LICENSE("GPL");