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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146// SPDX-License-Identifier: GPL-2.0/* * Sample kobject implementation * * Copyright (C) 2004-2007 Greg Kroah-Hartman <greg@kroah.com> * Copyright (C) 2007 Novell Inc. */#include <linux/kobject.h>#include <linux/string.h>#include <linux/sysfs.h>#include <linux/module.h>#include <linux/init.h>
/* * This module shows how to create a simple subdirectory in sysfs called * /sys/kernel/kobject_example In that directory, 3 files are created: * "foo", "baz", and "bar". If an integer is written to these files, it can be * later read out of it. */
static int foo;static int baz;static int bar;
/* * The "foo" file where a static variable is read from and written to. */static ssize_t foo_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf){ return sysfs_emit(buf, "%d\n", foo);}
static ssize_t foo_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count){ int ret;
ret = kstrtoint(buf, 10, &foo); if (ret < 0) return ret;
return count;}
/* Sysfs attributes cannot be world-writable. */static struct kobj_attribute foo_attribute = __ATTR(foo, 0664, foo_show, foo_store);
/* * More complex function where we determine which variable is being accessed by * looking at the attribute for the "baz" and "bar" files. */static ssize_t b_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf){ int var;
if (strcmp(attr->attr.name, "baz") == 0) var = baz; else var = bar; return sysfs_emit(buf, "%d\n", var);}
static ssize_t b_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count){ int var, ret;
ret = kstrtoint(buf, 10, &var); if (ret < 0) return ret;
if (strcmp(attr->attr.name, "baz") == 0) baz = var; else bar = var; return count;}
static struct kobj_attribute baz_attribute = __ATTR(baz, 0664, b_show, b_store);static struct kobj_attribute bar_attribute = __ATTR(bar, 0664, b_show, b_store);
/* * Create a group of attributes so that we can create and destroy them all * at once. */static struct attribute *attrs[] = { &foo_attribute.attr, &baz_attribute.attr, &bar_attribute.attr, NULL, /* need to NULL terminate the list of attributes */};
/* * An unnamed attribute group will put all of the attributes directly in * the kobject directory. If we specify a name, a subdirectory will be * created for the attributes with the directory being the name of the * attribute group. */static const struct attribute_group attr_group = { .attrs = attrs,};
static struct kobject *example_kobj;
static int __init example_init(void){ int retval;
/* * Create a simple kobject with the name of "kobject_example", * located under /sys/kernel/ * * As this is a simple directory, no uevent will be sent to * userspace. That is why this function should not be used for * any type of dynamic kobjects, where the name and number are * not known ahead of time. */ example_kobj = kobject_create_and_add("kobject_example", kernel_kobj); if (!example_kobj) return -ENOMEM;
/* Create the files associated with this kobject */ retval = sysfs_create_group(example_kobj, &attr_group); if (retval) kobject_put(example_kobj);
return retval;}
static void __exit example_exit(void){ kobject_put(example_kobj);}
module_init(example_init);module_exit(example_exit);MODULE_DESCRIPTION("Sample kobject implementation");MODULE_LICENSE("GPL v2");MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>");