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00977a59b9
Many struct file_operations in the kernel can be "const". Marking them const moves these to the .rodata section, which avoids false sharing with potential dirty data. In addition it'll catch accidental writes at compile time to these shared resources. Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
168 lines
3.5 KiB
C
168 lines
3.5 KiB
C
/*
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* Telephony registration for Linux
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*
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* (c) Copyright 1999 Red Hat Software Inc.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Author: Alan Cox, <alan@redhat.com>
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*
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* Fixes: Mar 01 2000 Thomas Sparr, <thomas.l.sparr@telia.com>
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* phone_register_device now works with unit!=PHONE_UNIT_ANY
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*/
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/string.h>
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#include <linux/errno.h>
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#include <linux/phonedev.h>
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#include <linux/init.h>
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#include <asm/uaccess.h>
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#include <asm/system.h>
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#include <linux/kmod.h>
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#include <linux/sem.h>
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#include <linux/mutex.h>
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#define PHONE_NUM_DEVICES 256
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/*
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* Active devices
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*/
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static struct phone_device *phone_device[PHONE_NUM_DEVICES];
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static DEFINE_MUTEX(phone_lock);
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/*
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* Open a phone device.
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*/
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static int phone_open(struct inode *inode, struct file *file)
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{
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unsigned int minor = iminor(inode);
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int err = 0;
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struct phone_device *p;
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const struct file_operations *old_fops, *new_fops = NULL;
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if (minor >= PHONE_NUM_DEVICES)
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return -ENODEV;
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mutex_lock(&phone_lock);
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p = phone_device[minor];
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if (p)
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new_fops = fops_get(p->f_op);
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if (!new_fops) {
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mutex_unlock(&phone_lock);
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request_module("char-major-%d-%d", PHONE_MAJOR, minor);
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mutex_lock(&phone_lock);
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p = phone_device[minor];
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if (p == NULL || (new_fops = fops_get(p->f_op)) == NULL)
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{
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err=-ENODEV;
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goto end;
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}
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}
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old_fops = file->f_op;
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file->f_op = new_fops;
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if (p->open)
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err = p->open(p, file); /* Tell the device it is open */
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if (err) {
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fops_put(file->f_op);
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file->f_op = fops_get(old_fops);
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}
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fops_put(old_fops);
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end:
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mutex_unlock(&phone_lock);
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return err;
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}
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/*
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* Telephony For Linux device drivers request registration here.
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*/
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int phone_register_device(struct phone_device *p, int unit)
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{
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int base;
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int end;
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int i;
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base = 0;
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end = PHONE_NUM_DEVICES - 1;
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if (unit != PHONE_UNIT_ANY) {
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base = unit;
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end = unit + 1; /* enter the loop at least one time */
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}
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mutex_lock(&phone_lock);
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for (i = base; i < end; i++) {
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if (phone_device[i] == NULL) {
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phone_device[i] = p;
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p->minor = i;
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mutex_unlock(&phone_lock);
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return 0;
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}
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}
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mutex_unlock(&phone_lock);
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return -ENFILE;
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}
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/*
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* Unregister an unused Telephony for linux device
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*/
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void phone_unregister_device(struct phone_device *pfd)
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{
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mutex_lock(&phone_lock);
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if (phone_device[pfd->minor] != pfd)
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panic("phone: bad unregister");
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phone_device[pfd->minor] = NULL;
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mutex_unlock(&phone_lock);
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}
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static const struct file_operations phone_fops =
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{
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.owner = THIS_MODULE,
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.open = phone_open,
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};
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/*
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* Board init functions
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*/
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/*
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* Initialise Telephony for linux
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*/
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static int __init telephony_init(void)
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{
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printk(KERN_INFO "Linux telephony interface: v1.00\n");
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if (register_chrdev(PHONE_MAJOR, "telephony", &phone_fops)) {
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printk("phonedev: unable to get major %d\n", PHONE_MAJOR);
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return -EIO;
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}
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return 0;
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}
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static void __exit telephony_exit(void)
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{
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unregister_chrdev(PHONE_MAJOR, "telephony");
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}
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module_init(telephony_init);
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module_exit(telephony_exit);
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MODULE_LICENSE("GPL");
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EXPORT_SYMBOL(phone_register_device);
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EXPORT_SYMBOL(phone_unregister_device);
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