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