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![Linus Torvalds](/assets/img/avatar_default.png)
Here is the set of driver core and kernfs changes for 6.2-rc1. The "big" change in here is the addition of a new macro, container_of_const() that will preserve the "const-ness" of a pointer passed into it. The "problem" of the current container_of() macro is that if you pass in a "const *", out of it can comes a non-const pointer unless you specifically ask for it. For many usages, we want to preserve the "const" attribute by using the same call. For a specific example, this series changes the kobj_to_dev() macro to use it, allowing it to be used no matter what the const value is. This prevents every subsystem from having to declare 2 different individual macros (i.e. kobj_const_to_dev() and kobj_to_dev()) and having the compiler enforce the const value at build time, which having 2 macros would not do either. The driver for all of this have been discussions with the Rust kernel developers as to how to properly mark driver core, and kobject, objects as being "non-mutable". The changes to the kobject and driver core in this pull request are the result of that, as there are lots of paths where kobjects and device pointers are not modified at all, so marking them as "const" allows the compiler to enforce this. So, a nice side affect of the Rust development effort has been already to clean up the driver core code to be more obvious about object rules. All of this has been bike-shedded in quite a lot of detail on lkml with different names and implementations resulting in the tiny version we have in here, much better than my original proposal. Lots of subsystem maintainers have acked the changes as well. Other than this change, included in here are smaller stuff like: - kernfs fixes and updates to handle lock contention better - vmlinux.lds.h fixes and updates - sysfs and debugfs documentation updates - device property updates All of these have been in the linux-next tree for quite a while with no problems, OTHER than some merge issues with other trees that should be obvious when you hit them (block tree deletes a driver that this tree modifies, iommufd tree modifies code that this tree also touches). If there are merge problems with these trees, please let me know. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> -----BEGIN PGP SIGNATURE----- iG0EABECAC0WIQT0tgzFv3jCIUoxPcsxR9QN2y37KQUCY5wz3A8cZ3JlZ0Brcm9h aC5jb20ACgkQMUfUDdst+yks0ACeKYUlVgCsER8eYW+x18szFa2QTXgAn2h/VhZe 1Fp53boFaQkGBjl8mGF8 =v+FB -----END PGP SIGNATURE----- Merge tag 'driver-core-6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core Pull driver core updates from Greg KH: "Here is the set of driver core and kernfs changes for 6.2-rc1. The "big" change in here is the addition of a new macro, container_of_const() that will preserve the "const-ness" of a pointer passed into it. The "problem" of the current container_of() macro is that if you pass in a "const *", out of it can comes a non-const pointer unless you specifically ask for it. For many usages, we want to preserve the "const" attribute by using the same call. For a specific example, this series changes the kobj_to_dev() macro to use it, allowing it to be used no matter what the const value is. This prevents every subsystem from having to declare 2 different individual macros (i.e. kobj_const_to_dev() and kobj_to_dev()) and having the compiler enforce the const value at build time, which having 2 macros would not do either. The driver for all of this have been discussions with the Rust kernel developers as to how to properly mark driver core, and kobject, objects as being "non-mutable". The changes to the kobject and driver core in this pull request are the result of that, as there are lots of paths where kobjects and device pointers are not modified at all, so marking them as "const" allows the compiler to enforce this. So, a nice side affect of the Rust development effort has been already to clean up the driver core code to be more obvious about object rules. All of this has been bike-shedded in quite a lot of detail on lkml with different names and implementations resulting in the tiny version we have in here, much better than my original proposal. Lots of subsystem maintainers have acked the changes as well. Other than this change, included in here are smaller stuff like: - kernfs fixes and updates to handle lock contention better - vmlinux.lds.h fixes and updates - sysfs and debugfs documentation updates - device property updates All of these have been in the linux-next tree for quite a while with no problems" * tag 'driver-core-6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (58 commits) device property: Fix documentation for fwnode_get_next_parent() firmware_loader: fix up to_fw_sysfs() to preserve const usb.h: take advantage of container_of_const() device.h: move kobj_to_dev() to use container_of_const() container_of: add container_of_const() that preserves const-ness of the pointer driver core: fix up missed drivers/s390/char/hmcdrv_dev.c class.devnode() conversion. driver core: fix up missed scsi/cxlflash class.devnode() conversion. driver core: fix up some missing class.devnode() conversions. driver core: make struct class.devnode() take a const * driver core: make struct class.dev_uevent() take a const * cacheinfo: Remove of_node_put() for fw_token device property: Add a blank line in Kconfig of tests device property: Rename goto label to be more precise device property: Move PROPERTY_ENTRY_BOOL() a bit down device property: Get rid of __PROPERTY_ENTRY_ARRAY_EL*SIZE*() kernfs: fix all kernel-doc warnings and multiple typos driver core: pass a const * into of_device_uevent() kobject: kset_uevent_ops: make name() callback take a const * kobject: kset_uevent_ops: make filter() callback take a const * kobject: make kobject_namespace take a const * ...
308 lines
7.1 KiB
C
308 lines
7.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/drivers/char/misc.c
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*
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* Generic misc open routine by Johan Myreen
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*
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* Based on code from Linus
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*
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* Teemu Rantanen's Microsoft Busmouse support and Derrick Cole's
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* changes incorporated into 0.97pl4
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* by Peter Cervasio (pete%q106fm.uucp@wupost.wustl.edu) (08SEP92)
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* See busmouse.c for particulars.
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*
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* Made things a lot mode modular - easy to compile in just one or two
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* of the misc drivers, as they are now completely independent. Linus.
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*
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* Support for loadable modules. 8-Sep-95 Philip Blundell <pjb27@cam.ac.uk>
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*
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* Fixed a failing symbol register to free the device registration
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* Alan Cox <alan@lxorguk.ukuu.org.uk> 21-Jan-96
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*
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* Dynamic minors and /proc/mice by Alessandro Rubini. 26-Mar-96
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*
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* Renamed to misc and miscdevice to be more accurate. Alan Cox 26-Mar-96
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*
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* Handling of mouse minor numbers for kerneld:
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* Idea by Jacques Gelinas <jack@solucorp.qc.ca>,
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* adapted by Bjorn Ekwall <bj0rn@blox.se>
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* corrected by Alan Cox <alan@lxorguk.ukuu.org.uk>
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*
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* Changes for kmod (from kerneld):
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* Cyrus Durgin <cider@speakeasy.org>
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*
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* Added devfs support. Richard Gooch <rgooch@atnf.csiro.au> 10-Jan-1998
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*/
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/errno.h>
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#include <linux/miscdevice.h>
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#include <linux/kernel.h>
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#include <linux/major.h>
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#include <linux/mutex.h>
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#include <linux/proc_fs.h>
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#include <linux/seq_file.h>
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#include <linux/stat.h>
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#include <linux/init.h>
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#include <linux/device.h>
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#include <linux/tty.h>
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#include <linux/kmod.h>
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#include <linux/gfp.h>
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/*
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* Head entry for the doubly linked miscdevice list
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*/
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static LIST_HEAD(misc_list);
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static DEFINE_MUTEX(misc_mtx);
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/*
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* Assigned numbers, used for dynamic minors
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*/
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#define DYNAMIC_MINORS 128 /* like dynamic majors */
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static DEFINE_IDA(misc_minors_ida);
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static int misc_minor_alloc(void)
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{
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int ret;
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ret = ida_alloc_max(&misc_minors_ida, DYNAMIC_MINORS - 1, GFP_KERNEL);
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if (ret >= 0) {
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ret = DYNAMIC_MINORS - ret - 1;
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} else {
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ret = ida_alloc_range(&misc_minors_ida, MISC_DYNAMIC_MINOR + 1,
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MINORMASK, GFP_KERNEL);
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}
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return ret;
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}
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static void misc_minor_free(int minor)
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{
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if (minor < DYNAMIC_MINORS)
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ida_free(&misc_minors_ida, DYNAMIC_MINORS - minor - 1);
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else if (minor > MISC_DYNAMIC_MINOR)
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ida_free(&misc_minors_ida, minor);
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}
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#ifdef CONFIG_PROC_FS
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static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
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{
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mutex_lock(&misc_mtx);
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return seq_list_start(&misc_list, *pos);
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}
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static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
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{
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return seq_list_next(v, &misc_list, pos);
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}
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static void misc_seq_stop(struct seq_file *seq, void *v)
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{
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mutex_unlock(&misc_mtx);
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}
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static int misc_seq_show(struct seq_file *seq, void *v)
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{
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const struct miscdevice *p = list_entry(v, struct miscdevice, list);
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seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
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return 0;
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}
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static const struct seq_operations misc_seq_ops = {
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.start = misc_seq_start,
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.next = misc_seq_next,
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.stop = misc_seq_stop,
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.show = misc_seq_show,
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};
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#endif
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static int misc_open(struct inode *inode, struct file *file)
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{
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int minor = iminor(inode);
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struct miscdevice *c = NULL, *iter;
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int err = -ENODEV;
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const struct file_operations *new_fops = NULL;
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mutex_lock(&misc_mtx);
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list_for_each_entry(iter, &misc_list, list) {
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if (iter->minor != minor)
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continue;
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c = iter;
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new_fops = fops_get(iter->fops);
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break;
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}
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if (!new_fops) {
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mutex_unlock(&misc_mtx);
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request_module("char-major-%d-%d", MISC_MAJOR, minor);
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mutex_lock(&misc_mtx);
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list_for_each_entry(iter, &misc_list, list) {
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if (iter->minor != minor)
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continue;
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c = iter;
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new_fops = fops_get(iter->fops);
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break;
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}
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if (!new_fops)
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goto fail;
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}
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/*
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* Place the miscdevice in the file's
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* private_data so it can be used by the
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* file operations, including f_op->open below
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*/
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file->private_data = c;
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err = 0;
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replace_fops(file, new_fops);
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if (file->f_op->open)
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err = file->f_op->open(inode, file);
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fail:
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mutex_unlock(&misc_mtx);
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return err;
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}
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static struct class *misc_class;
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static const struct file_operations misc_fops = {
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.owner = THIS_MODULE,
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.open = misc_open,
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.llseek = noop_llseek,
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};
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/**
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* misc_register - register a miscellaneous device
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* @misc: device structure
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*
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* Register a miscellaneous device with the kernel. If the minor
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* number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
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* and placed in the minor field of the structure. For other cases
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* the minor number requested is used.
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*
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* The structure passed is linked into the kernel and may not be
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* destroyed until it has been unregistered. By default, an open()
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* syscall to the device sets file->private_data to point to the
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* structure. Drivers don't need open in fops for this.
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*
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* A zero is returned on success and a negative errno code for
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* failure.
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*/
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int misc_register(struct miscdevice *misc)
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{
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dev_t dev;
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int err = 0;
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bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR);
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INIT_LIST_HEAD(&misc->list);
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mutex_lock(&misc_mtx);
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if (is_dynamic) {
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int i = misc_minor_alloc();
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if (i < 0) {
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err = -EBUSY;
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goto out;
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}
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misc->minor = i;
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} else {
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struct miscdevice *c;
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list_for_each_entry(c, &misc_list, list) {
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if (c->minor == misc->minor) {
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err = -EBUSY;
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goto out;
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}
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}
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}
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dev = MKDEV(MISC_MAJOR, misc->minor);
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misc->this_device =
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device_create_with_groups(misc_class, misc->parent, dev,
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misc, misc->groups, "%s", misc->name);
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if (IS_ERR(misc->this_device)) {
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if (is_dynamic) {
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misc_minor_free(misc->minor);
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misc->minor = MISC_DYNAMIC_MINOR;
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}
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err = PTR_ERR(misc->this_device);
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goto out;
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}
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/*
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* Add it to the front, so that later devices can "override"
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* earlier defaults
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*/
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list_add(&misc->list, &misc_list);
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out:
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mutex_unlock(&misc_mtx);
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return err;
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}
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EXPORT_SYMBOL(misc_register);
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/**
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* misc_deregister - unregister a miscellaneous device
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* @misc: device to unregister
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*
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* Unregister a miscellaneous device that was previously
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* successfully registered with misc_register().
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*/
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void misc_deregister(struct miscdevice *misc)
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{
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if (WARN_ON(list_empty(&misc->list)))
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return;
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mutex_lock(&misc_mtx);
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list_del(&misc->list);
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device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
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misc_minor_free(misc->minor);
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mutex_unlock(&misc_mtx);
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}
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EXPORT_SYMBOL(misc_deregister);
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static char *misc_devnode(const struct device *dev, umode_t *mode)
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{
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const struct miscdevice *c = dev_get_drvdata(dev);
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if (mode && c->mode)
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*mode = c->mode;
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if (c->nodename)
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return kstrdup(c->nodename, GFP_KERNEL);
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return NULL;
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}
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static int __init misc_init(void)
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{
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int err;
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struct proc_dir_entry *ret;
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ret = proc_create_seq("misc", 0, NULL, &misc_seq_ops);
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misc_class = class_create(THIS_MODULE, "misc");
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err = PTR_ERR(misc_class);
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if (IS_ERR(misc_class))
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goto fail_remove;
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err = -EIO;
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if (register_chrdev(MISC_MAJOR, "misc", &misc_fops))
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goto fail_printk;
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misc_class->devnode = misc_devnode;
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return 0;
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fail_printk:
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pr_err("unable to get major %d for misc devices\n", MISC_MAJOR);
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class_destroy(misc_class);
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fail_remove:
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if (ret)
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remove_proc_entry("misc", NULL);
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return err;
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}
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subsys_initcall(misc_init);
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