// 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 __ro_after_init; static DEFINE_MUTEX(chrdevs_lock); #define CHRDEV_MAJOR_HASH_SIZE … static struct char_device_struct { … } *chrdevs[CHRDEV_MAJOR_HASH_SIZE]; /* index in the above */ static inline int major_to_index(unsigned major) { … } #ifdef CONFIG_PROC_FS void chrdev_show(struct seq_file *f, off_t offset) { … } #endif /* CONFIG_PROC_FS */ static int find_dynamic_major(void) { … } /* * 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) { … } static struct char_device_struct * __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct) { … } /** * 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) { … } /** * 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) { … } /** * __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) { … } /** * 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) { … } /** * __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) { … } static DEFINE_SPINLOCK(cdev_lock); static struct kobject *cdev_get(struct cdev *p) { … } void cdev_put(struct cdev *p) { … } /* * Called every time a character special file is opened */ static int chrdev_open(struct inode *inode, struct file *filp) { … } void cd_forget(struct inode *inode) { … } static void cdev_purge(struct cdev *cdev) { … } /* * 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 = …; static struct kobject *exact_match(dev_t dev, int *part, void *data) { … } static int exact_lock(dev_t dev, void *data) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } static void cdev_unmap(dev_t dev, unsigned 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) { … } static void cdev_default_release(struct kobject *kobj) { … } static void cdev_dynamic_release(struct kobject *kobj) { … } static struct kobj_type ktype_cdev_default = …; static struct kobj_type ktype_cdev_dynamic = …; /** * cdev_alloc() - allocate a cdev structure * * Allocates and returns a cdev structure, or NULL on failure. */ struct cdev *cdev_alloc(void) { … } /** * 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) { … } static struct kobject *base_probe(dev_t dev, int *part, void *data) { … } void __init chrdev_init(void) { … } /* Let modules do char dev stuff */ EXPORT_SYMBOL(…); EXPORT_SYMBOL(…); EXPORT_SYMBOL(…); EXPORT_SYMBOL(…); EXPORT_SYMBOL(…); EXPORT_SYMBOL(…); EXPORT_SYMBOL(…); EXPORT_SYMBOL(…); EXPORT_SYMBOL(…); EXPORT_SYMBOL(…); EXPORT_SYMBOL(…); EXPORT_SYMBOL(…);
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