OSCL-LXR linux-6.0.1/​fs/​char_dev.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  *  linux/fs/char_dev.c
  *
  *  Copyright (C) 1991, 1992  Linus Torvalds
  */
 
 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/kdev_t.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 
 #include <linux/major.h>
 #include <linux/errno.h>
 #include <linux/module.h>
 #include <linux/seq_file.h>
 
 #include <linux/kobject.h>
 #include <linux/kobj_map.h>
 #include <linux/cdev.h>
 #include <linux/mutex.h>
 #include <linux/backing-dev.h>
 #include <linux/tty.h>
 
 #include "internal.h"
 
 static struct kobj_map *cdev_map;
 
 static DEFINE_MUTEX(chrdevs_lock);
 
 #define CHRDEV_MAJOR_HASH_SIZE 255
 
 static struct char_device_struct {
     struct char_device_struct *next;
     unsigned int major;
     unsigned int baseminor;
     int minorct;
     char name[64];
     struct cdev *cdev;      /* will die */
 } *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
 
 /* index in the above */
 static inline int major_to_index(unsigned major)
 {
     return major % CHRDEV_MAJOR_HASH_SIZE;
 }
 
 #ifdef CONFIG_PROC_FS
 
 void chrdev_show(struct seq_file *f, off_t offset)
 {
     struct char_device_struct *cd;
 
     mutex_lock(&chrdevs_lock);
     for (cd = chrdevs[major_to_index(offset)]; cd; cd = cd->next) {
         if (cd->major == offset)
             seq_printf(f, "%3d %s\n", cd->major, cd->name);
     }
     mutex_unlock(&chrdevs_lock);
 }
 
 #endif /* CONFIG_PROC_FS */
 
 static int find_dynamic_major(void)
 {
     int i;
     struct char_device_struct *cd;
 
     for (i = ARRAY_SIZE(chrdevs)-1; i >= CHRDEV_MAJOR_DYN_END; i--) {
         if (chrdevs[i] == NULL)
             return i;
     }
 
     for (i = CHRDEV_MAJOR_DYN_EXT_START;
          i >= CHRDEV_MAJOR_DYN_EXT_END; i--) {
         for (cd = chrdevs[major_to_index(i)]; cd; cd = cd->next)
             if (cd->major == i)
                 break;
 
         if (cd == NULL)
             return i;
     }
 
     return -EBUSY;
 }
 
 /*
  * Register a single major with a specified minor range.
  *
  * If major == 0 this function will dynamically allocate an unused major.
  * If major > 0 this function will attempt to reserve the range of minors
  * with given major.
  *
  */
 static struct char_device_struct *
 __register_chrdev_region(unsigned int major, unsigned int baseminor,
                int minorct, const char *name)
 {
     struct char_device_struct *cd, *curr, *prev = NULL;
     int ret;
     int i;
 
     if (major >= CHRDEV_MAJOR_MAX) {
         pr_err("CHRDEV \"%s\" major requested (%u) is greater than the maximum (%u)\n",
                name, major, CHRDEV_MAJOR_MAX-1);
         return ERR_PTR(-EINVAL);
     }
 
     if (minorct > MINORMASK + 1 - baseminor) {
         pr_err("CHRDEV \"%s\" minor range requested (%u-%u) is out of range of maximum range (%u-%u) for a single major\n",
             name, baseminor, baseminor + minorct - 1, 0, MINORMASK);
         return ERR_PTR(-EINVAL);
     }
 
     cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
     if (cd == NULL)
         return ERR_PTR(-ENOMEM);
 
     mutex_lock(&chrdevs_lock);
 
     if (major == 0) {
         ret = find_dynamic_major();
         if (ret < 0) {
             pr_err("CHRDEV \"%s\" dynamic allocation region is full\n",
                    name);
             goto out;
         }
         major = ret;
     }
 
     ret = -EBUSY;
     i = major_to_index(major);
     for (curr = chrdevs[i]; curr; prev = curr, curr = curr->next) {
         if (curr->major < major)
             continue;
 
         if (curr->major > major)
             break;
 
         if (curr->baseminor + curr->minorct <= baseminor)
             continue;
 
         if (curr->baseminor >= baseminor + minorct)
             break;
 
         goto out;
     }
 
     cd->major = major;
     cd->baseminor = baseminor;
     cd->minorct = minorct;
     strlcpy(cd->name, name, sizeof(cd->name));
 
     if (!prev) {
         cd->next = curr;
         chrdevs[i] = cd;
     } else {
         cd->next = prev->next;
         prev->next = cd;
     }
 
     mutex_unlock(&chrdevs_lock);
     return cd;
 out:
     mutex_unlock(&chrdevs_lock);
     kfree(cd);
     return ERR_PTR(ret);
 }
 
 static struct char_device_struct *
 __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
 {
     struct char_device_struct *cd = NULL, **cp;
     int i = major_to_index(major);
 
     mutex_lock(&chrdevs_lock);
     for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
         if ((*cp)->major == major &&
             (*cp)->baseminor == baseminor &&
             (*cp)->minorct == minorct)
             break;
     if (*cp) {
         cd = *cp;
         *cp = cd->next;
     }
     mutex_unlock(&chrdevs_lock);
     return cd;
 }
 
 /**
  * register_chrdev_region() - register a range of device numbers
  * @from: the first in the desired range of device numbers; must include
  *        the major number.
  * @count: the number of consecutive device numbers required
  * @name: the name of the device or driver.
  *
  * Return value is zero on success, a negative error code on failure.
  */
 int register_chrdev_region(dev_t from, unsigned count, const char *name)
 {
     struct char_device_struct *cd;
     dev_t to = from + count;
     dev_t n, next;
 
     for (n = from; n < to; n = next) {
         next = MKDEV(MAJOR(n)+1, 0);
         if (next > to)
             next = to;
         cd = __register_chrdev_region(MAJOR(n), MINOR(n),
                    next - n, name);
         if (IS_ERR(cd))
             goto fail;
     }
     return 0;
 fail:
     to = n;
     for (n = from; n < to; n = next) {
         next = MKDEV(MAJOR(n)+1, 0);
         kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
     }
     return PTR_ERR(cd);
 }
 
 /**
  * alloc_chrdev_region() - register a range of char device numbers
  * @dev: output parameter for first assigned number
  * @baseminor: first of the requested range of minor numbers
  * @count: the number of minor numbers required
  * @name: the name of the associated device or driver
  *
  * Allocates a range of char device numbers.  The major number will be
  * chosen dynamically, and returned (along with the first minor number)
  * in @dev.  Returns zero or a negative error code.
  */
 int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
             const char *name)
 {
     struct char_device_struct *cd;
     cd = __register_chrdev_region(0, baseminor, count, name);
     if (IS_ERR(cd))
         return PTR_ERR(cd);
     *dev = MKDEV(cd->major, cd->baseminor);
     return 0;
 }
 
 /**
  * __register_chrdev() - create and register a cdev occupying a range of minors
  * @major: major device number or 0 for dynamic allocation
  * @baseminor: first of the requested range of minor numbers
  * @count: the number of minor numbers required
  * @name: name of this range of devices
  * @fops: file operations associated with this devices
  *
  * If @major == 0 this functions will dynamically allocate a major and return
  * its number.
  *
  * If @major > 0 this function will attempt to reserve a device with the given
  * major number and will return zero on success.
  *
  * Returns a -ve errno on failure.
  *
  * The name of this device has nothing to do with the name of the device in
  * /dev. It only helps to keep track of the different owners of devices. If
  * your module name has only one type of devices it's ok to use e.g. the name
  * of the module here.
  */
 int __register_chrdev(unsigned int major, unsigned int baseminor,
               unsigned int count, const char *name,
               const struct file_operations *fops)
 {
     struct char_device_struct *cd;
     struct cdev *cdev;
     int err = -ENOMEM;
 
     cd = __register_chrdev_region(major, baseminor, count, name);
     if (IS_ERR(cd))
         return PTR_ERR(cd);
 
     cdev = cdev_alloc();
     if (!cdev)
         goto out2;
 
     cdev->owner = fops->owner;
     cdev->ops = fops;
     kobject_set_name(&cdev->kobj, "%s", name);
 
     err = cdev_add(cdev, MKDEV(cd->major, baseminor), count);
     if (err)
         goto out;
 
     cd->cdev = cdev;
 
     return major ? 0 : cd->major;
 out:
     kobject_put(&cdev->kobj);
 out2:
     kfree(__unregister_chrdev_region(cd->major, baseminor, count));
     return err;
 }
 
 /**
  * unregister_chrdev_region() - unregister a range of device numbers
  * @from: the first in the range of numbers to unregister
  * @count: the number of device numbers to unregister
  *
  * This function will unregister a range of @count device numbers,
  * starting with @from.  The caller should normally be the one who
  * allocated those numbers in the first place...
  */
 void unregister_chrdev_region(dev_t from, unsigned count)
 {
     dev_t to = from + count;
     dev_t n, next;
 
     for (n = from; n < to; n = next) {
         next = MKDEV(MAJOR(n)+1, 0);
         if (next > to)
             next = to;
         kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
     }
 }
 
 /**
  * __unregister_chrdev - unregister and destroy a cdev
  * @major: major device number
  * @baseminor: first of the range of minor numbers
  * @count: the number of minor numbers this cdev is occupying
  * @name: name of this range of devices
  *
  * Unregister and destroy the cdev occupying the region described by
  * @major, @baseminor and @count.  This function undoes what
  * __register_chrdev() did.
  */
 void __unregister_chrdev(unsigned int major, unsigned int baseminor,
              unsigned int count, const char *name)
 {
     struct char_device_struct *cd;
 
     cd = __unregister_chrdev_region(major, baseminor, count);
     if (cd && cd->cdev)
         cdev_del(cd->cdev);
     kfree(cd);
 }
 
 static DEFINE_SPINLOCK(cdev_lock);
 
 static struct kobject *cdev_get(struct cdev *p)
 {
     struct module *owner = p->owner;
     struct kobject *kobj;
 
     if (owner && !try_module_get(owner))
         return NULL;
     kobj = kobject_get_unless_zero(&p->kobj);
     if (!kobj)
         module_put(owner);
     return kobj;
 }
 
 void cdev_put(struct cdev *p)
 {
     if (p) {
         struct module *owner = p->owner;
         kobject_put(&p->kobj);
         module_put(owner);
     }
 }
 
 /*
  * Called every time a character special file is opened
  */
 static int chrdev_open(struct inode *inode, struct file *filp)
 {
     const struct file_operations *fops;
     struct cdev *p;
     struct cdev *new = NULL;
     int ret = 0;
 
     spin_lock(&cdev_lock);
     p = inode->i_cdev;
     if (!p) {
         struct kobject *kobj;
         int idx;
         spin_unlock(&cdev_lock);
         kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
         if (!kobj)
             return -ENXIO;
         new = container_of(kobj, struct cdev, kobj);
         spin_lock(&cdev_lock);
         /* Check i_cdev again in case somebody beat us to it while
            we dropped the lock. */
         p = inode->i_cdev;
         if (!p) {
             inode->i_cdev = p = new;
             list_add(&inode->i_devices, &p->list);
             new = NULL;
         } else if (!cdev_get(p))
             ret = -ENXIO;
     } else if (!cdev_get(p))
         ret = -ENXIO;
     spin_unlock(&cdev_lock);
     cdev_put(new);
     if (ret)
         return ret;
 
     ret = -ENXIO;
     fops = fops_get(p->ops);
     if (!fops)
         goto out_cdev_put;
 
     replace_fops(filp, fops);
     if (filp->f_op->open) {
         ret = filp->f_op->open(inode, filp);
         if (ret)
             goto out_cdev_put;
     }
 
     return 0;
 
  out_cdev_put:
     cdev_put(p);
     return ret;
 }
 
 void cd_forget(struct inode *inode)
 {
     spin_lock(&cdev_lock);
     list_del_init(&inode->i_devices);
     inode->i_cdev = NULL;
     inode->i_mapping = &inode->i_data;
     spin_unlock(&cdev_lock);
 }
 
 static void cdev_purge(struct cdev *cdev)
 {
     spin_lock(&cdev_lock);
     while (!list_empty(&cdev->list)) {
         struct inode *inode;
         inode = container_of(cdev->list.next, struct inode, i_devices);
         list_del_init(&inode->i_devices);
         inode->i_cdev = NULL;
     }
     spin_unlock(&cdev_lock);
 }
 
 /*
  * Dummy default file-operations: the only thing this does
  * is contain the open that then fills in the correct operations
  * depending on the special file...
  */
 const struct file_operations def_chr_fops = {
     .open = chrdev_open,
     .llseek = noop_llseek,
 };
 
 static struct kobject *exact_match(dev_t dev, int *part, void *data)
 {
     struct cdev *p = data;
     return &p->kobj;
 }
 
 static int exact_lock(dev_t dev, void *data)
 {
     struct cdev *p = data;
     return cdev_get(p) ? 0 : -1;
 }
 
 /**
  * cdev_add() - add a char device to the system
  * @p: the cdev structure for the device
  * @dev: the first device number for which this device is responsible
  * @count: the number of consecutive minor numbers corresponding to this
  *         device
  *
  * cdev_add() adds the device represented by @p to the system, making it
  * live immediately.  A negative error code is returned on failure.
  */
 int cdev_add(struct cdev *p, dev_t dev, unsigned count)
 {
     int error;
 
     p->dev = dev;
     p->count = count;
 
     if (WARN_ON(dev == WHITEOUT_DEV))
         return -EBUSY;
 
     error = kobj_map(cdev_map, dev, count, NULL,
              exact_match, exact_lock, p);
     if (error)
         return error;
 
     kobject_get(p->kobj.parent);
 
     return 0;
 }
 
 /**
  * cdev_set_parent() - set the parent kobject for a char device
  * @p: the cdev structure
  * @kobj: the kobject to take a reference to
  *
  * cdev_set_parent() sets a parent kobject which will be referenced
  * appropriately so the parent is not freed before the cdev. This
  * should be called before cdev_add.
  */
 void cdev_set_parent(struct cdev *p, struct kobject *kobj)
 {
     WARN_ON(!kobj->state_initialized);
     p->kobj.parent = kobj;
 }
 
 /**
  * cdev_device_add() - add a char device and it's corresponding
  *  struct device, linkink
  * @dev: the device structure
  * @cdev: the cdev structure
  *
  * cdev_device_add() adds the char device represented by @cdev to the system,
  * just as cdev_add does. It then adds @dev to the system using device_add
  * The dev_t for the char device will be taken from the struct device which
  * needs to be initialized first. This helper function correctly takes a
  * reference to the parent device so the parent will not get released until
  * all references to the cdev are released.
  *
  * This helper uses dev->devt for the device number. If it is not set
  * it will not add the cdev and it will be equivalent to device_add.
  *
  * This function should be used whenever the struct cdev and the
  * struct device are members of the same structure whose lifetime is
  * managed by the struct device.
  *
  * NOTE: Callers must assume that userspace was able to open the cdev and
  * can call cdev fops callbacks at any time, even if this function fails.
  */
 int cdev_device_add(struct cdev *cdev, struct device *dev)
 {
     int rc = 0;
 
     if (dev->devt) {
         cdev_set_parent(cdev, &dev->kobj);
 
         rc = cdev_add(cdev, dev->devt, 1);
         if (rc)
             return rc;
     }
 
     rc = device_add(dev);
     if (rc)
         cdev_del(cdev);
 
     return rc;
 }
 
 /**
  * cdev_device_del() - inverse of cdev_device_add
  * @dev: the device structure
  * @cdev: the cdev structure
  *
  * cdev_device_del() is a helper function to call cdev_del and device_del.
  * It should be used whenever cdev_device_add is used.
  *
  * If dev->devt is not set it will not remove the cdev and will be equivalent
  * to device_del.
  *
  * NOTE: This guarantees that associated sysfs callbacks are not running
  * or runnable, however any cdevs already open will remain and their fops
  * will still be callable even after this function returns.
  */
 void cdev_device_del(struct cdev *cdev, struct device *dev)
 {
     device_del(dev);
     if (dev->devt)
         cdev_del(cdev);
 }
 
 static void cdev_unmap(dev_t dev, unsigned count)
 {
     kobj_unmap(cdev_map, dev, count);
 }
 
 /**
  * cdev_del() - remove a cdev from the system
  * @p: the cdev structure to be removed
  *
  * cdev_del() removes @p from the system, possibly freeing the structure
  * itself.
  *
  * NOTE: This guarantees that cdev device will no longer be able to be
  * opened, however any cdevs already open will remain and their fops will
  * still be callable even after cdev_del returns.
  */
 void cdev_del(struct cdev *p)
 {
     cdev_unmap(p->dev, p->count);
     kobject_put(&p->kobj);
 }
 
 
 static void cdev_default_release(struct kobject *kobj)
 {
     struct cdev *p = container_of(kobj, struct cdev, kobj);
     struct kobject *parent = kobj->parent;
 
     cdev_purge(p);
     kobject_put(parent);
 }
 
 static void cdev_dynamic_release(struct kobject *kobj)
 {
     struct cdev *p = container_of(kobj, struct cdev, kobj);
     struct kobject *parent = kobj->parent;
 
     cdev_purge(p);
     kfree(p);
     kobject_put(parent);
 }
 
 static struct kobj_type ktype_cdev_default = {
     .release    = cdev_default_release,
 };
 
 static struct kobj_type ktype_cdev_dynamic = {
     .release    = cdev_dynamic_release,
 };
 
 /**
  * cdev_alloc() - allocate a cdev structure
  *
  * Allocates and returns a cdev structure, or NULL on failure.
  */
 struct cdev *cdev_alloc(void)
 {
     struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
     if (p) {
         INIT_LIST_HEAD(&p->list);
         kobject_init(&p->kobj, &ktype_cdev_dynamic);
     }
     return p;
 }
 
 /**
  * cdev_init() - initialize a cdev structure
  * @cdev: the structure to initialize
  * @fops: the file_operations for this device
  *
  * Initializes @cdev, remembering @fops, making it ready to add to the
  * system with cdev_add().
  */
 void cdev_init(struct cdev *cdev, const struct file_operations *fops)
 {
     memset(cdev, 0, sizeof *cdev);
     INIT_LIST_HEAD(&cdev->list);
     kobject_init(&cdev->kobj, &ktype_cdev_default);
     cdev->ops = fops;
 }
 
 static struct kobject *base_probe(dev_t dev, int *part, void *data)
 {
     if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
         /* Make old-style 2.4 aliases work */
         request_module("char-major-%d", MAJOR(dev));
     return NULL;
 }
 
 void __init chrdev_init(void)
 {
     cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
 }
 
 
 /* Let modules do char dev stuff */
 EXPORT_SYMBOL(register_chrdev_region);
 EXPORT_SYMBOL(unregister_chrdev_region);
 EXPORT_SYMBOL(alloc_chrdev_region);
 EXPORT_SYMBOL(cdev_init);
 EXPORT_SYMBOL(cdev_alloc);
 EXPORT_SYMBOL(cdev_del);
 EXPORT_SYMBOL(cdev_add);
 EXPORT_SYMBOL(cdev_set_parent);
 EXPORT_SYMBOL(cdev_device_add);
 EXPORT_SYMBOL(cdev_device_del);
 EXPORT_SYMBOL(__register_chrdev);
 EXPORT_SYMBOL(__unregister_chrdev);

This page was automatically generated by the 2.1.0 LXR engine. The LXR team