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 const 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 return 0; 194 } 195 196 static const struct file_operations media_devnode_fops = { 197 .owner = THIS_MODULE, 198 .read = media_read, 199 .write = media_write, 200 .open = media_open, 201 .unlocked_ioctl = media_ioctl, 202 #ifdef CONFIG_COMPAT 203 .compat_ioctl = media_compat_ioctl, 204 #endif /* CONFIG_COMPAT */ 205 .release = media_release, 206 .poll = media_poll, 207 .llseek = no_llseek, 208 }; 209 210 int __must_check media_devnode_register(struct media_device *mdev, 211 struct media_devnode *devnode, 212 struct module *owner) 213 { 214 int minor; 215 int ret; 216 217 /* Part 1: Find a free minor number */ 218 mutex_lock(&media_devnode_lock); 219 minor = find_first_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES); 220 if (minor == MEDIA_NUM_DEVICES) { 221 mutex_unlock(&media_devnode_lock); 222 pr_err("could not get a free minor\n"); 223 kfree(devnode); 224 return -ENFILE; 225 } 226 227 set_bit(minor, media_devnode_nums); 228 mutex_unlock(&media_devnode_lock); 229 230 devnode->minor = minor; 231 devnode->media_dev = mdev; 232 233 /* Part 1: Initialize dev now to use dev.kobj for cdev.kobj.parent */ 234 devnode->dev.bus = &media_bus_type; 235 devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor); 236 devnode->dev.release = media_devnode_release; 237 if (devnode->parent) 238 devnode->dev.parent = devnode->parent; 239 dev_set_name(&devnode->dev, "media%d", devnode->minor); 240 device_initialize(&devnode->dev); 241 242 /* Part 2: Initialize the character device */ 243 cdev_init(&devnode->cdev, &media_devnode_fops); 244 devnode->cdev.owner = owner; 245 kobject_set_name(&devnode->cdev.kobj, "media%d", devnode->minor); 246 247 /* Part 3: Add the media and char device */ 248 ret = cdev_device_add(&devnode->cdev, &devnode->dev); 249 if (ret < 0) { 250 pr_err("%s: cdev_device_add failed\n", __func__); 251 goto cdev_add_error; 252 } 253 254 /* Part 4: Activate this minor. The char device can now be used. */ 255 set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); 256 257 return 0; 258 259 cdev_add_error: 260 mutex_lock(&media_devnode_lock); 261 clear_bit(devnode->minor, media_devnode_nums); 262 devnode->media_dev = NULL; 263 mutex_unlock(&media_devnode_lock); 264 265 put_device(&devnode->dev); 266 return ret; 267 } 268 269 void media_devnode_unregister_prepare(struct media_devnode *devnode) 270 { 271 /* Check if devnode was ever registered at all */ 272 if (!media_devnode_is_registered(devnode)) 273 return; 274 275 mutex_lock(&media_devnode_lock); 276 clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); 277 mutex_unlock(&media_devnode_lock); 278 } 279 280 void media_devnode_unregister(struct media_devnode *devnode) 281 { 282 mutex_lock(&media_devnode_lock); 283 /* Delete the cdev on this minor as well */ 284 cdev_device_del(&devnode->cdev, &devnode->dev); 285 devnode->media_dev = NULL; 286 mutex_unlock(&media_devnode_lock); 287 288 put_device(&devnode->dev); 289 } 290 291 /* 292 * Initialise media for linux 293 */ 294 static int __init media_devnode_init(void) 295 { 296 int ret; 297 298 pr_info("Linux media interface: v0.10\n"); 299 ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES, 300 MEDIA_NAME); 301 if (ret < 0) { 302 pr_warn("unable to allocate major\n"); 303 return ret; 304 } 305 306 ret = bus_register(&media_bus_type); 307 if (ret < 0) { 308 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES); 309 pr_warn("bus_register failed\n"); 310 return -EIO; 311 } 312 313 return 0; 314 } 315 316 static void __exit media_devnode_exit(void) 317 { 318 bus_unregister(&media_bus_type); 319 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES); 320 } 321 322 subsys_initcall(media_devnode_init); 323 module_exit(media_devnode_exit) 324 325 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>"); 326 MODULE_DESCRIPTION("Device node registration for media drivers"); 327 MODULE_LICENSE("GPL"); 328