1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Media device node 4 * 5 * Copyright (C) 2010 Nokia Corporation 6 * 7 * Based on drivers/media/video/v4l2_dev.c code authored by 8 * Mauro Carvalho Chehab <mchehab@kernel.org> (version 2) 9 * Alan Cox, <alan@lxorguk.ukuu.org.uk> (version 1) 10 * 11 * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com> 12 * Sakari Ailus <sakari.ailus@iki.fi> 13 * 14 * -- 15 * 16 * Generic media device node infrastructure to register and unregister 17 * character devices using a dynamic major number and proper reference 18 * counting. 19 */ 20 21 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 22 23 #include <linux/errno.h> 24 #include <linux/init.h> 25 #include <linux/module.h> 26 #include <linux/kernel.h> 27 #include <linux/kmod.h> 28 #include <linux/slab.h> 29 #include <linux/mm.h> 30 #include <linux/string.h> 31 #include <linux/types.h> 32 #include <linux/uaccess.h> 33 34 #include <media/media-devnode.h> 35 #include <media/media-device.h> 36 37 #define MEDIA_NUM_DEVICES 256 38 #define MEDIA_NAME "media" 39 40 static dev_t media_dev_t; 41 42 /* 43 * Active devices 44 */ 45 static DEFINE_MUTEX(media_devnode_lock); 46 static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES); 47 48 /* debugfs */ 49 struct dentry *media_debugfs_root; 50 51 /* Called when the last user of the media device exits. */ 52 static void media_devnode_release(struct device *cd) 53 { 54 struct media_devnode *devnode = to_media_devnode(cd); 55 56 /* Release media_devnode and perform other cleanups as needed. */ 57 if (devnode->release) 58 devnode->release(devnode); 59 60 kfree(devnode); 61 pr_debug("%s: Media Devnode Deallocated\n", __func__); 62 } 63 64 static const struct bus_type media_bus_type = { 65 .name = MEDIA_NAME, 66 }; 67 68 static ssize_t media_read(struct file *filp, char __user *buf, 69 size_t sz, loff_t *off) 70 { 71 struct media_devnode *devnode = media_devnode_data(filp); 72 73 if (!devnode->fops->read) 74 return -EINVAL; 75 if (!media_devnode_is_registered(devnode)) 76 return -EIO; 77 return devnode->fops->read(filp, buf, sz, off); 78 } 79 80 static ssize_t media_write(struct file *filp, const char __user *buf, 81 size_t sz, loff_t *off) 82 { 83 struct media_devnode *devnode = media_devnode_data(filp); 84 85 if (!devnode->fops->write) 86 return -EINVAL; 87 if (!media_devnode_is_registered(devnode)) 88 return -EIO; 89 return devnode->fops->write(filp, buf, sz, off); 90 } 91 92 static __poll_t media_poll(struct file *filp, 93 struct poll_table_struct *poll) 94 { 95 struct media_devnode *devnode = media_devnode_data(filp); 96 97 if (!media_devnode_is_registered(devnode)) 98 return EPOLLERR | EPOLLHUP; 99 if (!devnode->fops->poll) 100 return DEFAULT_POLLMASK; 101 return devnode->fops->poll(filp, poll); 102 } 103 104 static long 105 __media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg, 106 long (*ioctl_func)(struct file *filp, unsigned int cmd, 107 unsigned long arg)) 108 { 109 struct media_devnode *devnode = media_devnode_data(filp); 110 111 if (!ioctl_func) 112 return -ENOTTY; 113 114 if (!media_devnode_is_registered(devnode)) 115 return -EIO; 116 117 return ioctl_func(filp, cmd, arg); 118 } 119 120 static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 121 { 122 struct media_devnode *devnode = media_devnode_data(filp); 123 124 return __media_ioctl(filp, cmd, arg, devnode->fops->ioctl); 125 } 126 127 #ifdef CONFIG_COMPAT 128 129 static long media_compat_ioctl(struct file *filp, unsigned int cmd, 130 unsigned long arg) 131 { 132 struct media_devnode *devnode = media_devnode_data(filp); 133 134 return __media_ioctl(filp, cmd, arg, devnode->fops->compat_ioctl); 135 } 136 137 #endif /* CONFIG_COMPAT */ 138 139 /* Override for the open function */ 140 static int media_open(struct inode *inode, struct file *filp) 141 { 142 struct media_devnode *devnode; 143 int ret; 144 145 /* Check if the media device is available. This needs to be done with 146 * the media_devnode_lock held to prevent an open/unregister race: 147 * without the lock, the device could be unregistered and freed between 148 * the media_devnode_is_registered() and get_device() calls, leading to 149 * a crash. 150 */ 151 mutex_lock(&media_devnode_lock); 152 devnode = container_of(inode->i_cdev, struct media_devnode, cdev); 153 /* return ENXIO if the media device has been removed 154 already or if it is not registered anymore. */ 155 if (!media_devnode_is_registered(devnode)) { 156 mutex_unlock(&media_devnode_lock); 157 return -ENXIO; 158 } 159 /* and increase the device refcount */ 160 get_device(&devnode->dev); 161 mutex_unlock(&media_devnode_lock); 162 163 filp->private_data = devnode; 164 165 if (devnode->fops->open) { 166 ret = devnode->fops->open(filp); 167 if (ret) { 168 put_device(&devnode->dev); 169 filp->private_data = NULL; 170 return ret; 171 } 172 } 173 174 return 0; 175 } 176 177 /* Override for the release function */ 178 static int media_release(struct inode *inode, struct file *filp) 179 { 180 struct media_devnode *devnode = media_devnode_data(filp); 181 182 if (devnode->fops->release) 183 devnode->fops->release(filp); 184 185 filp->private_data = NULL; 186 187 /* decrease the refcount unconditionally since the release() 188 return value is ignored. */ 189 put_device(&devnode->dev); 190 191 return 0; 192 } 193 194 static const struct file_operations media_devnode_fops = { 195 .owner = THIS_MODULE, 196 .read = media_read, 197 .write = media_write, 198 .open = media_open, 199 .unlocked_ioctl = media_ioctl, 200 #ifdef CONFIG_COMPAT 201 .compat_ioctl = media_compat_ioctl, 202 #endif /* CONFIG_COMPAT */ 203 .release = media_release, 204 .poll = media_poll, 205 }; 206 207 int __must_check media_devnode_register(struct media_device *mdev, 208 struct media_devnode *devnode, 209 struct module *owner) 210 { 211 int minor; 212 int ret; 213 214 /* Part 1: Find a free minor number */ 215 mutex_lock(&media_devnode_lock); 216 minor = find_first_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES); 217 if (minor == MEDIA_NUM_DEVICES) { 218 mutex_unlock(&media_devnode_lock); 219 pr_err("could not get a free minor\n"); 220 kfree(devnode); 221 return -ENFILE; 222 } 223 224 set_bit(minor, media_devnode_nums); 225 mutex_unlock(&media_devnode_lock); 226 227 devnode->minor = minor; 228 devnode->media_dev = mdev; 229 230 /* Part 1: Initialize dev now to use dev.kobj for cdev.kobj.parent */ 231 devnode->dev.bus = &media_bus_type; 232 devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor); 233 devnode->dev.release = media_devnode_release; 234 if (devnode->parent) 235 devnode->dev.parent = devnode->parent; 236 dev_set_name(&devnode->dev, "media%d", devnode->minor); 237 dev_set_drvdata(&devnode->dev, mdev); 238 device_initialize(&devnode->dev); 239 240 /* Part 2: Initialize the character device */ 241 cdev_init(&devnode->cdev, &media_devnode_fops); 242 devnode->cdev.owner = owner; 243 kobject_set_name(&devnode->cdev.kobj, "media%d", devnode->minor); 244 245 /* Part 3: Add the media and char device */ 246 set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); 247 ret = cdev_device_add(&devnode->cdev, &devnode->dev); 248 if (ret < 0) { 249 clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); 250 pr_err("%s: cdev_device_add failed\n", __func__); 251 goto cdev_add_error; 252 } 253 254 return 0; 255 256 cdev_add_error: 257 mutex_lock(&media_devnode_lock); 258 clear_bit(devnode->minor, media_devnode_nums); 259 devnode->media_dev = NULL; 260 mutex_unlock(&media_devnode_lock); 261 262 put_device(&devnode->dev); 263 return ret; 264 } 265 266 void media_devnode_unregister_prepare(struct media_devnode *devnode) 267 { 268 /* Check if devnode was ever registered at all */ 269 if (!media_devnode_is_registered(devnode)) 270 return; 271 272 mutex_lock(&media_devnode_lock); 273 clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); 274 mutex_unlock(&media_devnode_lock); 275 } 276 277 void media_devnode_unregister(struct media_devnode *devnode) 278 { 279 mutex_lock(&media_devnode_lock); 280 /* Delete the cdev on this minor as well */ 281 cdev_device_del(&devnode->cdev, &devnode->dev); 282 devnode->media_dev = NULL; 283 clear_bit(devnode->minor, media_devnode_nums); 284 mutex_unlock(&media_devnode_lock); 285 286 put_device(&devnode->dev); 287 } 288 289 /* 290 * Initialise media for linux 291 */ 292 static int __init media_devnode_init(void) 293 { 294 int ret; 295 296 pr_info("Linux media interface: v0.10\n"); 297 ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES, 298 MEDIA_NAME); 299 if (ret < 0) { 300 pr_warn("unable to allocate major\n"); 301 return ret; 302 } 303 304 ret = bus_register(&media_bus_type); 305 if (ret < 0) { 306 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES); 307 pr_warn("bus_register failed\n"); 308 return -EIO; 309 } 310 311 return 0; 312 } 313 314 static void __exit media_devnode_exit(void) 315 { 316 debugfs_remove_recursive(media_debugfs_root); 317 bus_unregister(&media_bus_type); 318 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES); 319 } 320 321 subsys_initcall(media_devnode_init); 322 module_exit(media_devnode_exit) 323 324 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>"); 325 MODULE_DESCRIPTION("Device node registration for media drivers"); 326 MODULE_LICENSE("GPL"); 327