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@infradead.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  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  25  *
  26  * --
  27  *
  28  * Generic media device node infrastructure to register and unregister
  29  * character devices using a dynamic major number and proper reference
  30  * counting.
  31  */
  32
  33 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  34
  35 #include <linux/errno.h>
  36 #include <linux/init.h>
  37 #include <linux/module.h>
  38 #include <linux/kernel.h>
  39 #include <linux/kmod.h>
  40 #include <linux/slab.h>
  41 #include <linux/mm.h>
  42 #include <linux/string.h>
  43 #include <linux/types.h>
  44 #include <linux/uaccess.h>
  45
  46 #include <media/media-devnode.h>
  47
  48 #define MEDIA_NUM_DEVICES       256
  49 #define MEDIA_NAME              "media"
  50
  51 static dev_t media_dev_t;
  52
  53 /*
  54  *      Active devices
  55  */
  56 static DEFINE_MUTEX(media_devnode_lock);
  57 static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
  58
  59 /* Called when the last user of the media device exits. */
  60 static void media_devnode_release(struct device *cd)
  61 {
  62         struct media_devnode *mdev = to_media_devnode(cd);
  63
  64         mutex_lock(&media_devnode_lock);
  65
  66         /* Delete the cdev on this minor as well */
  67         cdev_del(&mdev->cdev);
  68
  69         /* Mark device node number as free */
  70         clear_bit(mdev->minor, media_devnode_nums);
  71
  72         mutex_unlock(&media_devnode_lock);
  73
  74         /* Release media_devnode and perform other cleanups as needed. */
  75         if (mdev->release)
  76                 mdev->release(mdev);
  77 }
  78
  79 static struct bus_type media_bus_type = {
  80         .name = MEDIA_NAME,
  81 };
  82
  83 static ssize_t media_read(struct file *filp, char __user *buf,
  84                 size_t sz, loff_t *off)
  85 {
  86         struct media_devnode *mdev = media_devnode_data(filp);
  87
  88         if (!mdev->fops->read)
  89                 return -EINVAL;
  90         if (!media_devnode_is_registered(mdev))
  91                 return -EIO;
  92         return mdev->fops->read(filp, buf, sz, off);
  93 }
  94
  95 static ssize_t media_write(struct file *filp, const char __user *buf,
  96                 size_t sz, loff_t *off)
  97 {
  98         struct media_devnode *mdev = media_devnode_data(filp);
  99
 100         if (!mdev->fops->write)
 101                 return -EINVAL;
 102         if (!media_devnode_is_registered(mdev))
 103                 return -EIO;
 104         return mdev->fops->write(filp, buf, sz, off);
 105 }
 106
 107 static unsigned int media_poll(struct file *filp,
 108                                struct poll_table_struct *poll)
 109 {
 110         struct media_devnode *mdev = media_devnode_data(filp);
 111
 112         if (!media_devnode_is_registered(mdev))
 113                 return POLLERR | POLLHUP;
 114         if (!mdev->fops->poll)
 115                 return DEFAULT_POLLMASK;
 116         return mdev->fops->poll(filp, poll);
 117 }
 118
 119 static long
 120 __media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg,
 121               long (*ioctl_func)(struct file *filp, unsigned int cmd,
 122                                  unsigned long arg))
 123 {
 124         struct media_devnode *mdev = media_devnode_data(filp);
 125
 126         if (!ioctl_func)
 127                 return -ENOTTY;
 128
 129         if (!media_devnode_is_registered(mdev))
 130                 return -EIO;
 131
 132         return ioctl_func(filp, cmd, arg);
 133 }
 134
 135 static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 136 {
 137         struct media_devnode *mdev = media_devnode_data(filp);
 138
 139         return __media_ioctl(filp, cmd, arg, mdev->fops->ioctl);
 140 }
 141
 142 #ifdef CONFIG_COMPAT
 143
 144 static long media_compat_ioctl(struct file *filp, unsigned int cmd,
 145                                unsigned long arg)
 146 {
 147         struct media_devnode *mdev = media_devnode_data(filp);
 148
 149         return __media_ioctl(filp, cmd, arg, mdev->fops->compat_ioctl);
 150 }
 151
 152 #endif /* CONFIG_COMPAT */
 153
 154 /* Override for the open function */
 155 static int media_open(struct inode *inode, struct file *filp)
 156 {
 157         struct media_devnode *mdev;
 158         int ret;
 159
 160         /* Check if the media device is available. This needs to be done with
 161          * the media_devnode_lock held to prevent an open/unregister race:
 162          * without the lock, the device could be unregistered and freed between
 163          * the media_devnode_is_registered() and get_device() calls, leading to
 164          * a crash.
 165          */
 166         mutex_lock(&media_devnode_lock);
 167         mdev = container_of(inode->i_cdev, struct media_devnode, cdev);
 168         /* return ENXIO if the media device has been removed
 169            already or if it is not registered anymore. */
 170         if (!media_devnode_is_registered(mdev)) {
 171                 mutex_unlock(&media_devnode_lock);
 172                 return -ENXIO;
 173         }
 174         /* and increase the device refcount */
 175         get_device(&mdev->dev);
 176         mutex_unlock(&media_devnode_lock);
 177
 178         filp->private_data = mdev;
 179
 180         if (mdev->fops->open) {
 181                 ret = mdev->fops->open(filp);
 182                 if (ret) {
 183                         put_device(&mdev->dev);
 184                         return ret;
 185                 }
 186         }
 187
 188         return 0;
 189 }
 190
 191 /* Override for the release function */
 192 static int media_release(struct inode *inode, struct file *filp)
 193 {
 194         struct media_devnode *mdev = media_devnode_data(filp);
 195         int ret = 0;
 196
 197         if (mdev->fops->release)
 198                 mdev->fops->release(filp);
 199
 200         /* decrease the refcount unconditionally since the release()
 201            return value is ignored. */
 202         put_device(&mdev->dev);
 203         filp->private_data = NULL;
 204         return ret;
 205 }
 206
 207 static const struct file_operations media_devnode_fops = {
 208         .owner = THIS_MODULE,
 209         .read = media_read,
 210         .write = media_write,
 211         .open = media_open,
 212         .unlocked_ioctl = media_ioctl,
 213 #ifdef CONFIG_COMPAT
 214         .compat_ioctl = media_compat_ioctl,
 215 #endif /* CONFIG_COMPAT */
 216         .release = media_release,
 217         .poll = media_poll,
 218         .llseek = no_llseek,
 219 };
 220
 221 /**
 222  * media_devnode_register - register a media device node
 223  * @mdev: media device node structure we want to register
 224  *
 225  * The registration code assigns minor numbers and registers the new device node
 226  * with the kernel. An error is returned if no free minor number can be found,
 227  * or if the registration of the device node fails.
 228  *
 229  * Zero is returned on success.
 230  *
 231  * Note that if the media_devnode_register call fails, the release() callback of
 232  * the media_devnode structure is *not* called, so the caller is responsible for
 233  * freeing any data.
 234  */
 235 int __must_check media_devnode_register(struct media_devnode *mdev)
 236 {
 237         int minor;
 238         int ret;
 239
 240         /* Part 1: Find a free minor number */
 241         mutex_lock(&media_devnode_lock);
 242         minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
 243         if (minor == MEDIA_NUM_DEVICES) {
 244                 mutex_unlock(&media_devnode_lock);
 245                 pr_err("could not get a free minor\n");
 246                 return -ENFILE;
 247         }
 248
 249         set_bit(minor, media_devnode_nums);
 250         mutex_unlock(&media_devnode_lock);
 251
 252         mdev->minor = minor;
 253
 254         /* Part 2: Initialize and register the character device */
 255         cdev_init(&mdev->cdev, &media_devnode_fops);
 256         mdev->cdev.owner = mdev->fops->owner;
 257
 258         ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1);
 259         if (ret < 0) {
 260                 pr_err("%s: cdev_add failed\n", __func__);
 261                 goto error;
 262         }
 263
 264         /* Part 3: Register the media device */
 265         mdev->dev.bus = &media_bus_type;
 266         mdev->dev.devt = MKDEV(MAJOR(media_dev_t), mdev->minor);
 267         mdev->dev.release = media_devnode_release;
 268         if (mdev->parent)
 269                 mdev->dev.parent = mdev->parent;
 270         dev_set_name(&mdev->dev, "media%d", mdev->minor);
 271         ret = device_register(&mdev->dev);
 272         if (ret < 0) {
 273                 pr_err("%s: device_register failed\n", __func__);
 274                 goto error;
 275         }
 276
 277         /* Part 4: Activate this minor. The char device can now be used. */
 278         set_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
 279
 280         return 0;
 281
 282 error:
 283         cdev_del(&mdev->cdev);
 284         clear_bit(mdev->minor, media_devnode_nums);
 285         return ret;
 286 }
 287
 288 /**
 289  * media_devnode_unregister - unregister a media device node
 290  * @mdev: the device node to unregister
 291  *
 292  * This unregisters the passed device. Future open calls will be met with
 293  * errors.
 294  *
 295  * This function can safely be called if the device node has never been
 296  * registered or has already been unregistered.
 297  */
 298 void media_devnode_unregister(struct media_devnode *mdev)
 299 {
 300         /* Check if mdev was ever registered at all */
 301         if (!media_devnode_is_registered(mdev))
 302                 return;
 303
 304         mutex_lock(&media_devnode_lock);
 305         clear_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
 306         mutex_unlock(&media_devnode_lock);
 307         device_unregister(&mdev->dev);
 308 }
 309
 310 /*
 311  *      Initialise media for linux
 312  */
 313 static int __init media_devnode_init(void)
 314 {
 315         int ret;
 316
 317         pr_info("Linux media interface: v0.10\n");
 318         ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
 319                                   MEDIA_NAME);
 320         if (ret < 0) {
 321                 pr_warn("unable to allocate major\n");
 322                 return ret;
 323         }
 324
 325         ret = bus_register(&media_bus_type);
 326         if (ret < 0) {
 327                 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
 328                 pr_warn("bus_register failed\n");
 329                 return -EIO;
 330         }
 331
 332         return 0;
 333 }
 334
 335 static void __exit media_devnode_exit(void)
 336 {
 337         bus_unregister(&media_bus_type);
 338         unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
 339 }
 340
 341 subsys_initcall(media_devnode_init);
 342 module_exit(media_devnode_exit)
 343
 344 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
 345 MODULE_DESCRIPTION("Device node registration for media drivers");
 346 MODULE_LICENSE("GPL");