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1// SPDX-License-Identifier: GPL-2.02/*3 * linux/fs/char_dev.c4 *5 * Copyright (C) 1991, 1992 Linus Torvalds6 */7 8#include <linux/init.h>9#include <linux/fs.h>10#include <linux/kdev_t.h>11#include <linux/slab.h>12#include <linux/string.h>13 14#include <linux/major.h>15#include <linux/errno.h>16#include <linux/module.h>17#include <linux/seq_file.h>18 19#include <linux/kobject.h>20#include <linux/kobj_map.h>21#include <linux/cdev.h>22#include <linux/mutex.h>23#include <linux/backing-dev.h>24#include <linux/tty.h>25 26#include "internal.h"27 28static struct kobj_map *cdev_map __ro_after_init;29 30static DEFINE_MUTEX(chrdevs_lock);31 32#define CHRDEV_MAJOR_HASH_SIZE 25533 34static struct char_device_struct {35 struct char_device_struct *next;36 unsigned int major;37 unsigned int baseminor;38 int minorct;39 char name[64];40 struct cdev *cdev; /* will die */41} *chrdevs[CHRDEV_MAJOR_HASH_SIZE];42 43/* index in the above */44static inline int major_to_index(unsigned major)45{46 return major % CHRDEV_MAJOR_HASH_SIZE;47}48 49#ifdef CONFIG_PROC_FS50 51void chrdev_show(struct seq_file *f, off_t offset)52{53 struct char_device_struct *cd;54 55 mutex_lock(&chrdevs_lock);56 for (cd = chrdevs[major_to_index(offset)]; cd; cd = cd->next) {57 if (cd->major == offset)58 seq_printf(f, "%3d %s\n", cd->major, cd->name);59 }60 mutex_unlock(&chrdevs_lock);61}62 63#endif /* CONFIG_PROC_FS */64 65static int find_dynamic_major(void)66{67 int i;68 struct char_device_struct *cd;69 70 for (i = ARRAY_SIZE(chrdevs)-1; i >= CHRDEV_MAJOR_DYN_END; i--) {71 if (chrdevs[i] == NULL)72 return i;73 }74 75 for (i = CHRDEV_MAJOR_DYN_EXT_START;76 i >= CHRDEV_MAJOR_DYN_EXT_END; i--) {77 for (cd = chrdevs[major_to_index(i)]; cd; cd = cd->next)78 if (cd->major == i)79 break;80 81 if (cd == NULL)82 return i;83 }84 85 return -EBUSY;86}87 88/*89 * Register a single major with a specified minor range.90 *91 * If major == 0 this function will dynamically allocate an unused major.92 * If major > 0 this function will attempt to reserve the range of minors93 * with given major.94 *95 */96static HWJS_SUSPENDS struct char_device_struct *97__register_chrdev_region(unsigned int major, unsigned int baseminor,98 int minorct, const char *name)99{100 struct char_device_struct *cd, *curr, *prev = NULL;101 int ret;102 int i;103 104 if (major >= CHRDEV_MAJOR_MAX) {105 pr_err("CHRDEV \"%s\" major requested (%u) is greater than the maximum (%u)\n",106 name, major, CHRDEV_MAJOR_MAX-1);107 return ERR_PTR(-EINVAL);108 }109 110 if (minorct > MINORMASK + 1 - baseminor) {111 pr_err("CHRDEV \"%s\" minor range requested (%u-%u) is out of range of maximum range (%u-%u) for a single major\n",112 name, baseminor, baseminor + minorct - 1, 0, MINORMASK);113 return ERR_PTR(-EINVAL);114 }115 116 cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);117 if (cd == NULL)118 return ERR_PTR(-ENOMEM);119 120 mutex_lock(&chrdevs_lock);121 122 if (major == 0) {123 ret = find_dynamic_major();124 if (ret < 0) {125 pr_err("CHRDEV \"%s\" dynamic allocation region is full\n",126 name);127 goto out;128 }129 major = ret;130 }131 132 ret = -EBUSY;133 i = major_to_index(major);134 for (curr = chrdevs[i]; curr; prev = curr, curr = curr->next) {135 if (curr->major < major)136 continue;137 138 if (curr->major > major)139 break;140 141 if (curr->baseminor + curr->minorct <= baseminor)142 continue;143 144 if (curr->baseminor >= baseminor + minorct)145 break;146 147 goto out;148 }149 150 cd->major = major;151 cd->baseminor = baseminor;152 cd->minorct = minorct;153 strscpy(cd->name, name, sizeof(cd->name));154 155 if (!prev) {156 cd->next = curr;157 chrdevs[i] = cd;158 } else {159 cd->next = prev->next;160 prev->next = cd;161 }162 163 mutex_unlock(&chrdevs_lock);164 return cd;165out:166 mutex_unlock(&chrdevs_lock);167 kfree(cd);168 return ERR_PTR(ret);169}170 171static HWJS_SUSPENDS struct char_device_struct *172__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)173{174 struct char_device_struct *cd = NULL, **cp;175 int i = major_to_index(major);176 177 mutex_lock(&chrdevs_lock);178 for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)179 if ((*cp)->major == major &&180 (*cp)->baseminor == baseminor &&181 (*cp)->minorct == minorct)182 break;183 if (*cp) {184 cd = *cp;185 *cp = cd->next;186 }187 mutex_unlock(&chrdevs_lock);188 return cd;189}190 191/**192 * register_chrdev_region() - register a range of device numbers193 * @from: the first in the desired range of device numbers; must include194 * the major number.195 * @count: the number of consecutive device numbers required196 * @name: the name of the device or driver.197 *198 * Return value is zero on success, a negative error code on failure.199 */200int register_chrdev_region(dev_t from, unsigned count, const char *name)201{202 struct char_device_struct *cd;203 dev_t to = from + count;204 dev_t n, next;205 206 for (n = from; n < to; n = next) {207 next = MKDEV(MAJOR(n)+1, 0);208 if (next > to)209 next = to;210 cd = __register_chrdev_region(MAJOR(n), MINOR(n),211 next - n, name);212 if (IS_ERR(cd))213 goto fail;214 }215 return 0;216fail:217 to = n;218 for (n = from; n < to; n = next) {219 next = MKDEV(MAJOR(n)+1, 0);220 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));221 }222 return PTR_ERR(cd);223}224 225/**226 * alloc_chrdev_region() - register a range of char device numbers227 * @dev: output parameter for first assigned number228 * @baseminor: first of the requested range of minor numbers229 * @count: the number of minor numbers required230 * @name: the name of the associated device or driver231 *232 * Allocates a range of char device numbers. The major number will be233 * chosen dynamically, and returned (along with the first minor number)234 * in @dev. Returns zero or a negative error code.235 */236int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,237 const char *name)238{239 struct char_device_struct *cd;240 cd = __register_chrdev_region(0, baseminor, count, name);241 if (IS_ERR(cd))242 return PTR_ERR(cd);243 *dev = MKDEV(cd->major, cd->baseminor);244 return 0;245}246 247/**248 * __register_chrdev() - create and register a cdev occupying a range of minors249 * @major: major device number or 0 for dynamic allocation250 * @baseminor: first of the requested range of minor numbers251 * @count: the number of minor numbers required252 * @name: name of this range of devices253 * @fops: file operations associated with this devices254 *255 * If @major == 0 this functions will dynamically allocate a major and return256 * its number.257 *258 * If @major > 0 this function will attempt to reserve a device with the given259 * major number and will return zero on success.260 *261 * Returns a -ve errno on failure.262 *263 * The name of this device has nothing to do with the name of the device in264 * /dev. It only helps to keep track of the different owners of devices. If265 * your module name has only one type of devices it's ok to use e.g. the name266 * of the module here.267 */268int __register_chrdev(unsigned int major, unsigned int baseminor,269 unsigned int count, const char *name,270 const struct file_operations *fops)271{272 struct char_device_struct *cd;273 struct cdev *cdev;274 int err = -ENOMEM;275 276 cd = __register_chrdev_region(major, baseminor, count, name);277 if (IS_ERR(cd))278 return PTR_ERR(cd);279 280 cdev = cdev_alloc();281 if (!cdev)282 goto out2;283 284 cdev->owner = fops->owner;285 cdev->ops = fops;286 kobject_set_name(&cdev->kobj, "%s", name);287 288 err = cdev_add(cdev, MKDEV(cd->major, baseminor), count);289 if (err)290 goto out;291 292 cd->cdev = cdev;293 294 return major ? 0 : cd->major;295out:296 kobject_put(&cdev->kobj);297out2:298 kfree(__unregister_chrdev_region(cd->major, baseminor, count));299 return err;300}301 302/**303 * unregister_chrdev_region() - unregister a range of device numbers304 * @from: the first in the range of numbers to unregister305 * @count: the number of device numbers to unregister306 *307 * This function will unregister a range of @count device numbers,308 * starting with @from. The caller should normally be the one who309 * allocated those numbers in the first place...310 */311void unregister_chrdev_region(dev_t from, unsigned count)312{313 dev_t to = from + count;314 dev_t n, next;315 316 for (n = from; n < to; n = next) {317 next = MKDEV(MAJOR(n)+1, 0);318 if (next > to)319 next = to;320 kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));321 }322}323 324/**325 * __unregister_chrdev - unregister and destroy a cdev326 * @major: major device number327 * @baseminor: first of the range of minor numbers328 * @count: the number of minor numbers this cdev is occupying329 * @name: name of this range of devices330 *331 * Unregister and destroy the cdev occupying the region described by332 * @major, @baseminor and @count. This function undoes what333 * __register_chrdev() did.334 */335void __unregister_chrdev(unsigned int major, unsigned int baseminor,336 unsigned int count, const char *name)337{338 struct char_device_struct *cd;339 340 cd = __unregister_chrdev_region(major, baseminor, count);341 if (cd && cd->cdev)342 cdev_del(cd->cdev);343 kfree(cd);344}345 346static DEFINE_SPINLOCK(cdev_lock);347 348static struct kobject *cdev_get(struct cdev *p)349{350 struct module *owner = p->owner;351 struct kobject *kobj;352 353 if (!try_module_get(owner))354 return NULL;355 kobj = kobject_get_unless_zero(&p->kobj);356 if (!kobj)357 module_put(owner);358 return kobj;359}360 361void cdev_put(struct cdev *p)362{363 if (p) {364 struct module *owner = p->owner;365 kobject_put(&p->kobj);366 module_put(owner);367 }368}369 370/*371 * Called every time a character special file is opened372 */373static int chrdev_open(struct inode *inode, struct file *filp)374{375 const struct file_operations *fops;376 struct cdev *p;377 struct cdev *new = NULL;378 int ret = 0;379 380 spin_lock(&cdev_lock);381 p = inode->i_cdev;382 if (!p) {383 struct kobject *kobj;384 int idx;385 spin_unlock(&cdev_lock);386 kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);387 if (!kobj)388 return -ENXIO;389 new = container_of(kobj, struct cdev, kobj);390 spin_lock(&cdev_lock);391 /* Check i_cdev again in case somebody beat us to it while392 we dropped the lock. */393 p = inode->i_cdev;394 if (!p) {395 inode->i_cdev = p = new;396 list_add(&inode->i_devices, &p->list);397 new = NULL;398 } else if (!cdev_get(p))399 ret = -ENXIO;400 } else if (!cdev_get(p))401 ret = -ENXIO;402 spin_unlock(&cdev_lock);403 cdev_put(new);404 if (ret)405 return ret;406 407 ret = -ENXIO;408 fops = fops_get(p->ops);409 if (!fops)410 goto out_cdev_put;411 412 replace_fops(filp, fops);413 if (filp->f_op->open) {414 ret = filp->f_op->open(inode, filp);415 if (ret)416 goto out_cdev_put;417 }418 419 return 0;420 421 out_cdev_put:422 cdev_put(p);423 return ret;424}425 426void cd_forget(struct inode *inode)427{428 spin_lock(&cdev_lock);429 list_del_init(&inode->i_devices);430 inode->i_cdev = NULL;431 inode->i_mapping = &inode->i_data;432 spin_unlock(&cdev_lock);433}434 435static void cdev_purge(struct cdev *cdev)436{437 spin_lock(&cdev_lock);438 while (!list_empty(&cdev->list)) {439 struct inode *inode;440 inode = container_of(cdev->list.next, struct inode, i_devices);441 list_del_init(&inode->i_devices);442 inode->i_cdev = NULL;443 }444 spin_unlock(&cdev_lock);445}446 447/*448 * Dummy default file-operations: the only thing this does449 * is contain the open that then fills in the correct operations450 * depending on the special file...451 */452const struct file_operations def_chr_fops = {453 .open = chrdev_open,454 .llseek = noop_llseek,455};456 457static struct kobject *exact_match(dev_t dev, int *part, void *data)458{459 struct cdev *p = data;460 return &p->kobj;461}462 463static int exact_lock(dev_t dev, void *data)464{465 struct cdev *p = data;466 return cdev_get(p) ? 0 : -1;467}468 469/**470 * cdev_add() - add a char device to the system471 * @p: the cdev structure for the device472 * @dev: the first device number for which this device is responsible473 * @count: the number of consecutive minor numbers corresponding to this474 * device475 *476 * cdev_add() adds the device represented by @p to the system, making it477 * live immediately. A negative error code is returned on failure.478 */479int cdev_add(struct cdev *p, dev_t dev, unsigned count)480{481 int error;482 483 p->dev = dev;484 p->count = count;485 486 if (WARN_ON(dev == WHITEOUT_DEV)) {487 error = -EBUSY;488 goto err;489 }490 491 error = kobj_map(cdev_map, dev, count, NULL,492 exact_match, exact_lock, p);493 if (error)494 goto err;495 496 kobject_get(p->kobj.parent);497 498 return 0;499 500err:501 kfree_const(p->kobj.name);502 p->kobj.name = NULL;503 return error;504}505 506/**507 * cdev_set_parent() - set the parent kobject for a char device508 * @p: the cdev structure509 * @kobj: the kobject to take a reference to510 *511 * cdev_set_parent() sets a parent kobject which will be referenced512 * appropriately so the parent is not freed before the cdev. This513 * should be called before cdev_add.514 */515void cdev_set_parent(struct cdev *p, struct kobject *kobj)516{517 WARN_ON(!kobj->state_initialized);518 p->kobj.parent = kobj;519}520 521/**522 * cdev_device_add() - add a char device and it's corresponding523 * struct device, linkink524 * @dev: the device structure525 * @cdev: the cdev structure526 *527 * cdev_device_add() adds the char device represented by @cdev to the system,528 * just as cdev_add does. It then adds @dev to the system using device_add529 * The dev_t for the char device will be taken from the struct device which530 * needs to be initialized first. This helper function correctly takes a531 * reference to the parent device so the parent will not get released until532 * all references to the cdev are released.533 *534 * This helper uses dev->devt for the device number. If it is not set535 * it will not add the cdev and it will be equivalent to device_add.536 *537 * This function should be used whenever the struct cdev and the538 * struct device are members of the same structure whose lifetime is539 * managed by the struct device.540 *541 * NOTE: Callers must assume that userspace was able to open the cdev and542 * can call cdev fops callbacks at any time, even if this function fails.543 */544int cdev_device_add(struct cdev *cdev, struct device *dev)545{546 int rc = 0;547 548 if (dev->devt) {549 cdev_set_parent(cdev, &dev->kobj);550 551 rc = cdev_add(cdev, dev->devt, 1);552 if (rc)553 return rc;554 }555 556 rc = device_add(dev);557 if (rc && dev->devt)558 cdev_del(cdev);559 560 return rc;561}562 563/**564 * cdev_device_del() - inverse of cdev_device_add565 * @dev: the device structure566 * @cdev: the cdev structure567 *568 * cdev_device_del() is a helper function to call cdev_del and device_del.569 * It should be used whenever cdev_device_add is used.570 *571 * If dev->devt is not set it will not remove the cdev and will be equivalent572 * to device_del.573 *574 * NOTE: This guarantees that associated sysfs callbacks are not running575 * or runnable, however any cdevs already open will remain and their fops576 * will still be callable even after this function returns.577 */578void cdev_device_del(struct cdev *cdev, struct device *dev)579{580 device_del(dev);581 if (dev->devt)582 cdev_del(cdev);583}584 585static void cdev_unmap(dev_t dev, unsigned count)586{587 kobj_unmap(cdev_map, dev, count);588}589 590/**591 * cdev_del() - remove a cdev from the system592 * @p: the cdev structure to be removed593 *594 * cdev_del() removes @p from the system, possibly freeing the structure595 * itself.596 *597 * NOTE: This guarantees that cdev device will no longer be able to be598 * opened, however any cdevs already open will remain and their fops will599 * still be callable even after cdev_del returns.600 */601void cdev_del(struct cdev *p)602{603 cdev_unmap(p->dev, p->count);604 kobject_put(&p->kobj);605}606 607 608static void cdev_default_release(struct kobject *kobj)609{610 struct cdev *p = container_of(kobj, struct cdev, kobj);611 struct kobject *parent = kobj->parent;612 613 cdev_purge(p);614 kobject_put(parent);615}616 617static void cdev_dynamic_release(struct kobject *kobj)618{619 struct cdev *p = container_of(kobj, struct cdev, kobj);620 struct kobject *parent = kobj->parent;621 622 cdev_purge(p);623 kfree(p);624 kobject_put(parent);625}626 627static struct kobj_type ktype_cdev_default = {628 .release = cdev_default_release,629};630 631static struct kobj_type ktype_cdev_dynamic = {632 .release = cdev_dynamic_release,633};634 635/**636 * cdev_alloc() - allocate a cdev structure637 *638 * Allocates and returns a cdev structure, or NULL on failure.639 */640struct cdev *cdev_alloc(void)641{642 struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);643 if (p) {644 INIT_LIST_HEAD(&p->list);645 kobject_init(&p->kobj, &ktype_cdev_dynamic);646 }647 return p;648}649 650/**651 * cdev_init() - initialize a cdev structure652 * @cdev: the structure to initialize653 * @fops: the file_operations for this device654 *655 * Initializes @cdev, remembering @fops, making it ready to add to the656 * system with cdev_add().657 */658void cdev_init(struct cdev *cdev, const struct file_operations *fops)659{660 memset(cdev, 0, sizeof *cdev);661 INIT_LIST_HEAD(&cdev->list);662 kobject_init(&cdev->kobj, &ktype_cdev_default);663 cdev->ops = fops;664}665 666static struct kobject *base_probe(dev_t dev, int *part, void *data)667{668 if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)669 /* Make old-style 2.4 aliases work */670 request_module("char-major-%d", MAJOR(dev));671 return NULL;672}673 674void __init chrdev_init(void)675{676 cdev_map = kobj_map_init(base_probe, &chrdevs_lock);677}678 679 680/* Let modules do char dev stuff */681EXPORT_SYMBOL(register_chrdev_region);682EXPORT_SYMBOL(unregister_chrdev_region);683EXPORT_SYMBOL(alloc_chrdev_region);684EXPORT_SYMBOL(cdev_init);685EXPORT_SYMBOL(cdev_alloc);686EXPORT_SYMBOL(cdev_del);687EXPORT_SYMBOL(cdev_add);688EXPORT_SYMBOL(cdev_set_parent);689EXPORT_SYMBOL(cdev_device_add);690EXPORT_SYMBOL(cdev_device_del);691EXPORT_SYMBOL(__register_chrdev);692EXPORT_SYMBOL(__unregister_chrdev);693