add task 9
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52
README.md
52
README.md
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@ -230,6 +230,58 @@ ls -l /sys/kernel/debug/eudyptula/
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* [Chapitre 3, Linux Device Drivers, 3rd Edition](https://lwn.net/Kernel/LDD3/)
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* [Jiffies, Linux Kernel Development 2nd Edition](https://litux.nl/mirror/kerneldevelopment/0672327201/ch10lev1sec3.html)
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### Tache 9
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Idem que la tache 8 pour tester les sémaphores.
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```bash
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ls -l /sys/eudyptula/
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# total 0
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# -rw-r--r-- 1 root root 4096 Jan 23 18:42 foo
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# -rw-rw-rw- 1 root root 4096 Jan 23 18:42 id
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# -r--r--r-- 1 root root 4096 Jan 23 18:42 jiffies
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echo pouet > /sys/eudyptula/foo
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cat /sys/eudyptula/foo
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# pouet
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echo coucou ! > /sys/eudyptula/foo
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cat /sys/eudyptula/foo
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# coucou !
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cat /sys/eudyptula/id
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# pouetpouet
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echo -n congruent > /sys/eudyptula/id
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echo $?
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# 0
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echo pouet > /sys/eudyptula/id
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# bash: echo: write error: Invalid argument
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echo $?
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# 1
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echo pouet > /sys/eudyptula/jiffies
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# bash: /sys/eudyptula/jiffies: Permission denied
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cat /sys/eudyptula/jiffies
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# 4344413015
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cat /sys/eudyptula/jiffies
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# 4344413465
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echo pouet > /sys/eudyptula/foo &
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cat /sys/eudyptula/foo
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# cat: /sys/eudyptula/foo: Invalid argument
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cat /sys/eudyptula/foo &
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cat /sys/eudyptula/foo &
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echo pouet > /sys/eudyptula/foo
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# bash: echo: write error: Invalid argument
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rmmod sysfs
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ls -l /sys/eudyptula/
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# ls: cannot access '/sys/eudyptula/': No such file or directory
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```
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* [The zen of kobjects](https://lwn.net/Articles/51437/) : un peu vieux, certaines fonctions pas
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à jour
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* [kobjects and sysfs](https://lwn.net/Articles/54651/) : idem
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* [Everything you never wanted to know about kobjects, ksets, and
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ktypes](https://docs.kernel.org/core-api/kobject.html) (documentation noyau)
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* [Exemple de code pour
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`kobject`](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/samples/kobject)
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* [Chapitre 14, Linux Device Drivers, 3rd Edition](https://lwn.net/Kernel/LDD3/)
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## Informations diverses
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Je liste dans cette section quelques informations que j'ai pu découvrir en
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9
task_09/Makefile
Normal file
9
task_09/Makefile
Normal file
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@ -0,0 +1,9 @@
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obj-m += sysfs.o
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PWD := $(CURDIR)
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all:
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make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
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clean:
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make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
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189
task_09/sysfs.c
Normal file
189
task_09/sysfs.c
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@ -0,0 +1,189 @@
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// SPDX-License-Identifier: GPL-2.0
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#define DEBUG 1
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#include <asm/page.h>
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#include <linux/kernel.h>
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#include <linux/kobject.h>
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#include <linux/jiffies.h>
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#include <linux/module.h>
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#include <linux/rwsem.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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#include <linux/sysfs.h>
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#ifdef DEBUG
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#include <linux/delay.h>
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#endif
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#define BUFFER_LENGTH 10
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// représente un dossier sur sysfs
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static struct kobject eudyptula;
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// représente un fichier sur sysfs
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static struct attribute id_file = {
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.name = "id",
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.mode = 0666
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};
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static struct attribute jiffies_file = {
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.name = "jiffies",
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.mode = 0444
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};
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static struct attribute foo_file = {
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.name = "foo",
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.mode = 0644
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};
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static char *id_msg;
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static char *foo_msg;
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static struct rw_semaphore foo_sem;
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/*
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* fonctions pour pouvoir lire et écrire dans les fichiers. elles sont ici
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* découpées pour mieux se rendre compte. Il faut cependant les appeler depuis
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* les fonctions se trouvant plus bas.
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*/
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static ssize_t id_read(char *buffer)
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{
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return sysfs_emit(buffer, id_msg);
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}
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static ssize_t id_write(const char *buffer, size_t size)
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{
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int ret = -EINVAL;
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if (!strcmp(buffer, "congruent"))
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ret = size;
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return ret;
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}
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static ssize_t jiffies_read(char *buffer)
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{
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return sprintf(buffer, "%lld\n", jiffies_64);
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}
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static ssize_t foo_read(char *buffer)
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{
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int ret = -EINVAL;
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if (down_read_trylock(&foo_sem)) {
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ret = sysfs_emit(buffer, foo_msg);
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#ifdef DEBUG
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msleep(5000);
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#endif
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up_read(&foo_sem);
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}
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return ret;
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}
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static ssize_t foo_write(const char *buffer, size_t count)
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{
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int ret = -EINVAL;
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if (down_write_trylock(&foo_sem)) {
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ret = strscpy(foo_msg, buffer, count + 1);
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#ifdef DEBUG
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msleep(5000);
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#endif
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up_write(&foo_sem);
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}
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return ret;
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}
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/*
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* fonctions utilisées pour lire et écrire dans les attributes. Elles sont
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* mises dans une structure sysfs_ops et mis à l'initialisation du kobject via
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* un ktype.
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*/
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ssize_t show(struct kobject *kobj, struct attribute *attr, char *buffer)
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{
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ssize_t ret = 0;
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if (!strcmp(attr->name, "id"))
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ret = id_read(buffer);
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else if (!strcmp(attr->name, "jiffies"))
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ret = jiffies_read(buffer);
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else if (!strcmp(attr->name, "foo"))
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ret = foo_read(buffer);
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else
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pr_info("keske tu essaies de lire ?!");
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return ret;
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}
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ssize_t store(struct kobject *kobj, struct attribute *attr, const char *buffer,
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size_t len)
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{
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ssize_t ret = 0;
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if (!strcmp(attr->name, "id"))
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ret = id_write(buffer, len);
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else if (!strcmp(attr->name, "foo"))
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ret = foo_write(buffer, len);
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else
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pr_info("keske tu essaies d'ecrire ?!");
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return ret;
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}
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static const struct sysfs_ops my_ops = {
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.show = &show,
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.store = &store,
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};
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static const struct kobj_type my_type = {
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.sysfs_ops = &my_ops,
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};
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static int __init my_init(void)
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{
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pr_info("Coucou le gens !!!!\n");
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if (!memset(&eudyptula, 0, sizeof(struct kobject)))
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return -ENOMEM;
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if (kobject_init_and_add(&eudyptula, &my_type, NULL, "eudyptula")) {
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kobject_put(&eudyptula);
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return -ENOMEM;
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}
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if (sysfs_create_file(&eudyptula, &id_file)
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|| sysfs_create_file(&eudyptula, &jiffies_file)
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|| sysfs_create_file(&eudyptula, &foo_file)) {
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kobject_put(&eudyptula);
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return -ENOMEM;
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}
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init_rwsem(&foo_sem);
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id_msg = kmalloc(12, GFP_KERNEL);
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foo_msg = kmalloc(PAGE_SIZE, GFP_KERNEL);
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strscpy(id_msg, "pouetpouet\n", 12);
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return 0;
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}
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static void __exit my_exit(void)
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{
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sysfs_remove_file(&eudyptula, &id_file);
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sysfs_remove_file(&eudyptula, &jiffies_file);
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sysfs_remove_file(&eudyptula, &foo_file);
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kobject_put(&eudyptula);
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kfree(id_msg);
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kfree(foo_msg);
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pr_info("Tschuss !!!\n");
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}
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module_init(my_init);
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module_exit(my_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("rick <rick@gnous.eu>");
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MODULE_DESCRIPTION("Module pour tester le sysfs.");
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