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