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 /* Called when the last user of the media device exits. */ 49 static void media_devnode_release(struct device *cd) 50 { 51 struct media_devnode *devnode = to_media_devnode(cd); 52 53 mutex_lock(&media_devnode_lock); 54 /* Mark device node number as free */ 55 clear_bit(devnode->minor, media_devnode_nums); 56 mutex_unlock(&media_devnode_lock); 57 58 /* Release media_devnode and perform other cleanups as needed. */ 59 if (devnode->release) 60 devnode->release(devnode); 61 62 kfree(devnode); 63 pr_debug("%s: Media Devnode Deallocated\n", __func__); 64 } 65 66 static struct bus_type media_bus_type = { 67 .name = MEDIA_NAME, 68 }; 69 70 static ssize_t media_read(struct file *filp, char __user *buf, 71 size_t sz, loff_t *off) 72 { 73 struct media_devnode *devnode = media_devnode_data(filp); 74 75 if (!devnode->fops->read) 76 return -EINVAL; 77 if (!media_devnode_is_registered(devnode)) 78 return -EIO; 79 return devnode->fops->read(filp, buf, sz, off); 80 } 81 82 static ssize_t media_write(struct file *filp, const 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->write) 88 return -EINVAL; 89 if (!media_devnode_is_registered(devnode)) 90 return -EIO; 91 return devnode->fops->write(filp, buf, sz, off); 92 } 93 94 static __poll_t media_poll(struct file *filp, 95 struct poll_table_struct *poll) 96 { 97 struct media_devnode *devnode = media_devnode_data(filp); 98 99 if (!media_devnode_is_registered(devnode)) 100 return EPOLLERR | EPOLLHUP; 101 if (!devnode->fops->poll) 102 return DEFAULT_POLLMASK; 103 return devnode->fops->poll(filp, poll); 104 } 105 106 static long 107 __media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg, 108 long (*ioctl_func)(struct file *filp, unsigned int cmd, 109 unsigned long arg)) 110 { 111 struct media_devnode *devnode = media_devnode_data(filp); 112 113 if (!ioctl_func) 114 return -ENOTTY; 115 116 if (!media_devnode_is_registered(devnode)) 117 return -EIO; 118 119 return ioctl_func(filp, cmd, arg); 120 } 121 122 static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 123 { 124 struct media_devnode *devnode = media_devnode_data(filp); 125 126 return __media_ioctl(filp, cmd, arg, devnode->fops->ioctl); 127 } 128 129 #ifdef CONFIG_COMPAT 130 131 static long media_compat_ioctl(struct file *filp, unsigned int cmd, 132 unsigned long arg) 133 { 134 struct media_devnode *devnode = media_devnode_data(filp); 135 136 return __media_ioctl(filp, cmd, arg, devnode->fops->compat_ioctl); 137 } 138 139 #endif /* CONFIG_COMPAT */ 140 141 /* Override for the open function */ 142 static int media_open(struct inode *inode, struct file *filp) 143 { 144 struct media_devnode *devnode; 145 int ret; 146 147 /* Check if the media device is available. This needs to be done with 148 * the media_devnode_lock held to prevent an open/unregister race: 149 * without the lock, the device could be unregistered and freed between 150 * the media_devnode_is_registered() and get_device() calls, leading to 151 * a crash. 152 */ 153 mutex_lock(&media_devnode_lock); 154 devnode = container_of(inode->i_cdev, struct media_devnode, cdev); 155 /* return ENXIO if the media device has been removed 156 already or if it is not registered anymore. */ 157 if (!media_devnode_is_registered(devnode)) { 158 mutex_unlock(&media_devnode_lock); 159 return -ENXIO; 160 } 161 /* and increase the device refcount */ 162 get_device(&devnode->dev); 163 mutex_unlock(&media_devnode_lock); 164 165 filp->private_data = devnode; 166 167 if (devnode->fops->open) { 168 ret = devnode->fops->open(filp); 169 if (ret) { 170 put_device(&devnode->dev); 171 filp->private_data = NULL; 172 return ret; 173 } 174 } 175 176 return 0; 177 } 178 179 /* Override for the release function */ 180 static int media_release(struct inode *inode, struct file *filp) 181 { 182 struct media_devnode *devnode = media_devnode_data(filp); 183 184 if (devnode->fops->release) 185 devnode->fops->release(filp); 186 187 filp->private_data = NULL; 188 189 /* decrease the refcount unconditionally since the release() 190 return value is ignored. */ 191 put_device(&devnode->dev); 192 193 pr_debug("%s: Media Release\n", __func__); 194 return 0; 195 } 196 197 static const struct file_operations media_devnode_fops = { 198 .owner = THIS_MODULE, 199 .read = media_read, 200 .write = media_write, 201 .open = media_open, 202 .unlocked_ioctl = media_ioctl, 203 #ifdef CONFIG_COMPAT 204 .compat_ioctl = media_compat_ioctl, 205 #endif /* CONFIG_COMPAT */ 206 .release = media_release, 207 .poll = media_poll, 208 .llseek = no_llseek, 209 }; 210 211 int __must_check media_devnode_register(struct media_device *mdev, 212 struct media_devnode *devnode, 213 struct module *owner) 214 { 215 int minor; 216 int ret; 217 218 /* Part 1: Find a free minor number */ 219 mutex_lock(&media_devnode_lock); 220 minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0); 221 if (minor == MEDIA_NUM_DEVICES) { 222 mutex_unlock(&media_devnode_lock); 223 pr_err("could not get a free minor\n"); 224 kfree(devnode); 225 return -ENFILE; 226 } 227 228 set_bit(minor, media_devnode_nums); 229 mutex_unlock(&media_devnode_lock); 230 231 devnode->minor = minor; 232 devnode->media_dev = mdev; 233 234 /* Part 1: Initialize dev now to use dev.kobj for cdev.kobj.parent */ 235 devnode->dev.bus = &media_bus_type; 236 devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor); 237 devnode->dev.release = media_devnode_release; 238 if (devnode->parent) 239 devnode->dev.parent = devnode->parent; 240 dev_set_name(&devnode->dev, "media%d", devnode->minor); 241 device_initialize(&devnode->dev); 242 243 /* Part 2: Initialize the character device */ 244 cdev_init(&devnode->cdev, &media_devnode_fops); 245 devnode->cdev.owner = owner; 246 kobject_set_name(&devnode->cdev.kobj, "media%d", devnode->minor); 247 248 /* Part 3: Add the media and char device */ 249 ret = cdev_device_add(&devnode->cdev, &devnode->dev); 250 if (ret < 0) { 251 pr_err("%s: cdev_device_add failed\n", __func__); 252 goto cdev_add_error; 253 } 254 255 /* Part 4: Activate this minor. The char device can now be used. */ 256 set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); 257 258 return 0; 259 260 cdev_add_error: 261 mutex_lock(&media_devnode_lock); 262 clear_bit(devnode->minor, media_devnode_nums); 263 devnode->media_dev = NULL; 264 mutex_unlock(&media_devnode_lock); 265 266 put_device(&devnode->dev); 267 return ret; 268 } 269 270 void media_devnode_unregister_prepare(struct media_devnode *devnode) 271 { 272 /* Check if devnode was ever registered at all */ 273 if (!media_devnode_is_registered(devnode)) 274 return; 275 276 mutex_lock(&media_devnode_lock); 277 clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); 278 mutex_unlock(&media_devnode_lock); 279 } 280 281 void media_devnode_unregister(struct media_devnode *devnode) 282 { 283 mutex_lock(&media_devnode_lock); 284 /* Delete the cdev on this minor as well */ 285 cdev_device_del(&devnode->cdev, &devnode->dev); 286 devnode->media_dev = NULL; 287 mutex_unlock(&media_devnode_lock); 288 289 put_device(&devnode->dev); 290 } 291 292 /* 293 * Initialise media for linux 294 */ 295 static int __init media_devnode_init(void) 296 { 297 int ret; 298 299 pr_info("Linux media interface: v0.10\n"); 300 ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES, 301 MEDIA_NAME); 302 if (ret < 0) { 303 pr_warn("unable to allocate major\n"); 304 return ret; 305 } 306 307 ret = bus_register(&media_bus_type); 308 if (ret < 0) { 309 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES); 310 pr_warn("bus_register failed\n"); 311 return -EIO; 312 } 313 314 return 0; 315 } 316 317 static void __exit media_devnode_exit(void) 318 { 319 bus_unregister(&media_bus_type); 320 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES); 321 } 322 323 subsys_initcall(media_devnode_init); 324 module_exit(media_devnode_exit) 325 326 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>"); 327 MODULE_DESCRIPTION("Device node registration for media drivers"); 328 MODULE_LICENSE("GPL"); 329