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 /* Release media_devnode and perform other cleanups as needed. */ 54 if (devnode->release) 55 devnode->release(devnode); 56 57 kfree(devnode); 58 pr_debug("%s: Media Devnode Deallocated\n", __func__); 59 } 60 61 static const struct bus_type media_bus_type = { 62 .name = MEDIA_NAME, 63 }; 64 65 static ssize_t media_read(struct file *filp, char __user *buf, 66 size_t sz, loff_t *off) 67 { 68 struct media_devnode *devnode = media_devnode_data(filp); 69 70 if (!devnode->fops->read) 71 return -EINVAL; 72 if (!media_devnode_is_registered(devnode)) 73 return -EIO; 74 return devnode->fops->read(filp, buf, sz, off); 75 } 76 77 static ssize_t media_write(struct file *filp, const char __user *buf, 78 size_t sz, loff_t *off) 79 { 80 struct media_devnode *devnode = media_devnode_data(filp); 81 82 if (!devnode->fops->write) 83 return -EINVAL; 84 if (!media_devnode_is_registered(devnode)) 85 return -EIO; 86 return devnode->fops->write(filp, buf, sz, off); 87 } 88 89 static __poll_t media_poll(struct file *filp, 90 struct poll_table_struct *poll) 91 { 92 struct media_devnode *devnode = media_devnode_data(filp); 93 94 if (!media_devnode_is_registered(devnode)) 95 return EPOLLERR | EPOLLHUP; 96 if (!devnode->fops->poll) 97 return DEFAULT_POLLMASK; 98 return devnode->fops->poll(filp, poll); 99 } 100 101 static long 102 __media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg, 103 long (*ioctl_func)(struct file *filp, unsigned int cmd, 104 unsigned long arg)) 105 { 106 struct media_devnode *devnode = media_devnode_data(filp); 107 108 if (!ioctl_func) 109 return -ENOTTY; 110 111 if (!media_devnode_is_registered(devnode)) 112 return -EIO; 113 114 return ioctl_func(filp, cmd, arg); 115 } 116 117 static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 118 { 119 struct media_devnode *devnode = media_devnode_data(filp); 120 121 return __media_ioctl(filp, cmd, arg, devnode->fops->ioctl); 122 } 123 124 #ifdef CONFIG_COMPAT 125 126 static long media_compat_ioctl(struct file *filp, unsigned int cmd, 127 unsigned long arg) 128 { 129 struct media_devnode *devnode = media_devnode_data(filp); 130 131 return __media_ioctl(filp, cmd, arg, devnode->fops->compat_ioctl); 132 } 133 134 #endif /* CONFIG_COMPAT */ 135 136 /* Override for the open function */ 137 static int media_open(struct inode *inode, struct file *filp) 138 { 139 struct media_devnode *devnode; 140 int ret; 141 142 /* Check if the media device is available. This needs to be done with 143 * the media_devnode_lock held to prevent an open/unregister race: 144 * without the lock, the device could be unregistered and freed between 145 * the media_devnode_is_registered() and get_device() calls, leading to 146 * a crash. 147 */ 148 mutex_lock(&media_devnode_lock); 149 devnode = container_of(inode->i_cdev, struct media_devnode, cdev); 150 /* return ENXIO if the media device has been removed 151 already or if it is not registered anymore. */ 152 if (!media_devnode_is_registered(devnode)) { 153 mutex_unlock(&media_devnode_lock); 154 return -ENXIO; 155 } 156 /* and increase the device refcount */ 157 get_device(&devnode->dev); 158 mutex_unlock(&media_devnode_lock); 159 160 filp->private_data = devnode; 161 162 if (devnode->fops->open) { 163 ret = devnode->fops->open(filp); 164 if (ret) { 165 put_device(&devnode->dev); 166 filp->private_data = NULL; 167 return ret; 168 } 169 } 170 171 return 0; 172 } 173 174 /* Override for the release function */ 175 static int media_release(struct inode *inode, struct file *filp) 176 { 177 struct media_devnode *devnode = media_devnode_data(filp); 178 179 if (devnode->fops->release) 180 devnode->fops->release(filp); 181 182 filp->private_data = NULL; 183 184 /* decrease the refcount unconditionally since the release() 185 return value is ignored. */ 186 put_device(&devnode->dev); 187 188 return 0; 189 } 190 191 static const struct file_operations media_devnode_fops = { 192 .owner = THIS_MODULE, 193 .read = media_read, 194 .write = media_write, 195 .open = media_open, 196 .unlocked_ioctl = media_ioctl, 197 #ifdef CONFIG_COMPAT 198 .compat_ioctl = media_compat_ioctl, 199 #endif /* CONFIG_COMPAT */ 200 .release = media_release, 201 .poll = media_poll, 202 }; 203 204 int __must_check media_devnode_register(struct media_device *mdev, 205 struct media_devnode *devnode, 206 struct module *owner) 207 { 208 int minor; 209 int ret; 210 211 /* Part 1: Find a free minor number */ 212 mutex_lock(&media_devnode_lock); 213 minor = find_first_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES); 214 if (minor == MEDIA_NUM_DEVICES) { 215 mutex_unlock(&media_devnode_lock); 216 pr_err("could not get a free minor\n"); 217 kfree(devnode); 218 return -ENFILE; 219 } 220 221 set_bit(minor, media_devnode_nums); 222 mutex_unlock(&media_devnode_lock); 223 224 devnode->minor = minor; 225 devnode->media_dev = mdev; 226 227 /* Part 1: Initialize dev now to use dev.kobj for cdev.kobj.parent */ 228 devnode->dev.bus = &media_bus_type; 229 devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor); 230 devnode->dev.release = media_devnode_release; 231 if (devnode->parent) 232 devnode->dev.parent = devnode->parent; 233 dev_set_name(&devnode->dev, "media%d", devnode->minor); 234 device_initialize(&devnode->dev); 235 236 /* Part 2: Initialize the character device */ 237 cdev_init(&devnode->cdev, &media_devnode_fops); 238 devnode->cdev.owner = owner; 239 kobject_set_name(&devnode->cdev.kobj, "media%d", devnode->minor); 240 241 /* Part 3: Add the media and char device */ 242 set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); 243 ret = cdev_device_add(&devnode->cdev, &devnode->dev); 244 if (ret < 0) { 245 clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); 246 pr_err("%s: cdev_device_add failed\n", __func__); 247 goto cdev_add_error; 248 } 249 250 return 0; 251 252 cdev_add_error: 253 mutex_lock(&media_devnode_lock); 254 clear_bit(devnode->minor, media_devnode_nums); 255 devnode->media_dev = NULL; 256 mutex_unlock(&media_devnode_lock); 257 258 put_device(&devnode->dev); 259 return ret; 260 } 261 262 void media_devnode_unregister_prepare(struct media_devnode *devnode) 263 { 264 /* Check if devnode was ever registered at all */ 265 if (!media_devnode_is_registered(devnode)) 266 return; 267 268 mutex_lock(&media_devnode_lock); 269 clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); 270 mutex_unlock(&media_devnode_lock); 271 } 272 273 void media_devnode_unregister(struct media_devnode *devnode) 274 { 275 mutex_lock(&media_devnode_lock); 276 /* Delete the cdev on this minor as well */ 277 cdev_device_del(&devnode->cdev, &devnode->dev); 278 devnode->media_dev = NULL; 279 clear_bit(devnode->minor, media_devnode_nums); 280 mutex_unlock(&media_devnode_lock); 281 282 put_device(&devnode->dev); 283 } 284 285 /* 286 * Initialise media for linux 287 */ 288 static int __init media_devnode_init(void) 289 { 290 int ret; 291 292 pr_info("Linux media interface: v0.10\n"); 293 ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES, 294 MEDIA_NAME); 295 if (ret < 0) { 296 pr_warn("unable to allocate major\n"); 297 return ret; 298 } 299 300 ret = bus_register(&media_bus_type); 301 if (ret < 0) { 302 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES); 303 pr_warn("bus_register failed\n"); 304 return -EIO; 305 } 306 307 return 0; 308 } 309 310 static void __exit media_devnode_exit(void) 311 { 312 bus_unregister(&media_bus_type); 313 unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES); 314 } 315 316 subsys_initcall(media_devnode_init); 317 module_exit(media_devnode_exit) 318 319 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>"); 320 MODULE_DESCRIPTION("Device node registration for media drivers"); 321 MODULE_LICENSE("GPL"); 322