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288 lines
7.0 KiB
288 lines
7.0 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Sample kset and ktype implementation |
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* |
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* Copyright (C) 2004-2007 Greg Kroah-Hartman <[email protected]> |
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* Copyright (C) 2007 Novell Inc. |
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*/ |
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#include <linux/kobject.h> |
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#include <linux/string.h> |
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#include <linux/sysfs.h> |
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#include <linux/slab.h> |
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#include <linux/module.h> |
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#include <linux/init.h> |
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/* |
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* This module shows how to create a kset in sysfs called |
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* /sys/kernel/kset-example |
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* Then tree kobjects are created and assigned to this kset, "foo", "baz", |
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* and "bar". In those kobjects, attributes of the same name are also |
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* created and if an integer is written to these files, it can be later |
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* read out of it. |
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*/ |
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/* |
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* This is our "object" that we will create a few of and register them with |
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* sysfs. |
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*/ |
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struct foo_obj { |
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struct kobject kobj; |
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int foo; |
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int baz; |
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int bar; |
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}; |
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#define to_foo_obj(x) container_of(x, struct foo_obj, kobj) |
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/* a custom attribute that works just for a struct foo_obj. */ |
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struct foo_attribute { |
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struct attribute attr; |
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ssize_t (*show)(struct foo_obj *foo, struct foo_attribute *attr, char *buf); |
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ssize_t (*store)(struct foo_obj *foo, struct foo_attribute *attr, const char *buf, size_t count); |
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}; |
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#define to_foo_attr(x) container_of(x, struct foo_attribute, attr) |
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/* |
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* The default show function that must be passed to sysfs. This will be |
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* called by sysfs for whenever a show function is called by the user on a |
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* sysfs file associated with the kobjects we have registered. We need to |
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* transpose back from a "default" kobject to our custom struct foo_obj and |
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* then call the show function for that specific object. |
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*/ |
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static ssize_t foo_attr_show(struct kobject *kobj, |
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struct attribute *attr, |
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char *buf) |
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{ |
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struct foo_attribute *attribute; |
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struct foo_obj *foo; |
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attribute = to_foo_attr(attr); |
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foo = to_foo_obj(kobj); |
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if (!attribute->show) |
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return -EIO; |
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return attribute->show(foo, attribute, buf); |
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} |
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/* |
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* Just like the default show function above, but this one is for when the |
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* sysfs "store" is requested (when a value is written to a file.) |
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*/ |
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static ssize_t foo_attr_store(struct kobject *kobj, |
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struct attribute *attr, |
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const char *buf, size_t len) |
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{ |
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struct foo_attribute *attribute; |
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struct foo_obj *foo; |
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attribute = to_foo_attr(attr); |
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foo = to_foo_obj(kobj); |
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if (!attribute->store) |
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return -EIO; |
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return attribute->store(foo, attribute, buf, len); |
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} |
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/* Our custom sysfs_ops that we will associate with our ktype later on */ |
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static const struct sysfs_ops foo_sysfs_ops = { |
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.show = foo_attr_show, |
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.store = foo_attr_store, |
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}; |
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/* |
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* The release function for our object. This is REQUIRED by the kernel to |
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* have. We free the memory held in our object here. |
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* |
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* NEVER try to get away with just a "blank" release function to try to be |
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* smarter than the kernel. Turns out, no one ever is... |
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*/ |
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static void foo_release(struct kobject *kobj) |
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{ |
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struct foo_obj *foo; |
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foo = to_foo_obj(kobj); |
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kfree(foo); |
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} |
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/* |
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* The "foo" file where the .foo variable is read from and written to. |
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*/ |
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static ssize_t foo_show(struct foo_obj *foo_obj, struct foo_attribute *attr, |
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char *buf) |
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{ |
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return sprintf(buf, "%d\n", foo_obj->foo); |
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} |
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static ssize_t foo_store(struct foo_obj *foo_obj, struct foo_attribute *attr, |
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const char *buf, size_t count) |
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{ |
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int ret; |
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ret = kstrtoint(buf, 10, &foo_obj->foo); |
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if (ret < 0) |
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return ret; |
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return count; |
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} |
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/* Sysfs attributes cannot be world-writable. */ |
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static struct foo_attribute foo_attribute = |
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__ATTR(foo, 0664, foo_show, foo_store); |
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/* |
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* More complex function where we determine which variable is being accessed by |
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* looking at the attribute for the "baz" and "bar" files. |
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*/ |
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static ssize_t b_show(struct foo_obj *foo_obj, struct foo_attribute *attr, |
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char *buf) |
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{ |
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int var; |
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if (strcmp(attr->attr.name, "baz") == 0) |
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var = foo_obj->baz; |
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else |
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var = foo_obj->bar; |
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return sprintf(buf, "%d\n", var); |
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} |
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static ssize_t b_store(struct foo_obj *foo_obj, struct foo_attribute *attr, |
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const char *buf, size_t count) |
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{ |
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int var, ret; |
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ret = kstrtoint(buf, 10, &var); |
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if (ret < 0) |
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return ret; |
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if (strcmp(attr->attr.name, "baz") == 0) |
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foo_obj->baz = var; |
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else |
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foo_obj->bar = var; |
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return count; |
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} |
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static struct foo_attribute baz_attribute = |
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__ATTR(baz, 0664, b_show, b_store); |
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static struct foo_attribute bar_attribute = |
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__ATTR(bar, 0664, b_show, b_store); |
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/* |
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* Create a group of attributes so that we can create and destroy them all |
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* at once. |
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*/ |
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static struct attribute *foo_default_attrs[] = { |
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&foo_attribute.attr, |
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&baz_attribute.attr, |
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&bar_attribute.attr, |
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NULL, /* need to NULL terminate the list of attributes */ |
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}; |
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ATTRIBUTE_GROUPS(foo_default); |
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/* |
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* Our own ktype for our kobjects. Here we specify our sysfs ops, the |
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* release function, and the set of default attributes we want created |
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* whenever a kobject of this type is registered with the kernel. |
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*/ |
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static struct kobj_type foo_ktype = { |
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.sysfs_ops = &foo_sysfs_ops, |
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.release = foo_release, |
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.default_groups = foo_default_groups, |
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}; |
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static struct kset *example_kset; |
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static struct foo_obj *foo_obj; |
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static struct foo_obj *bar_obj; |
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static struct foo_obj *baz_obj; |
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static struct foo_obj *create_foo_obj(const char *name) |
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{ |
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struct foo_obj *foo; |
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int retval; |
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/* allocate the memory for the whole object */ |
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foo = kzalloc(sizeof(*foo), GFP_KERNEL); |
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if (!foo) |
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return NULL; |
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/* |
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* As we have a kset for this kobject, we need to set it before calling |
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* the kobject core. |
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*/ |
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foo->kobj.kset = example_kset; |
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/* |
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* Initialize and add the kobject to the kernel. All the default files |
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* will be created here. As we have already specified a kset for this |
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* kobject, we don't have to set a parent for the kobject, the kobject |
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* will be placed beneath that kset automatically. |
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*/ |
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retval = kobject_init_and_add(&foo->kobj, &foo_ktype, NULL, "%s", name); |
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if (retval) { |
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kobject_put(&foo->kobj); |
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return NULL; |
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} |
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/* |
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* We are always responsible for sending the uevent that the kobject |
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* was added to the system. |
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*/ |
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kobject_uevent(&foo->kobj, KOBJ_ADD); |
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return foo; |
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} |
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static void destroy_foo_obj(struct foo_obj *foo) |
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{ |
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kobject_put(&foo->kobj); |
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} |
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static int __init example_init(void) |
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{ |
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/* |
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* Create a kset with the name of "kset_example", |
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* located under /sys/kernel/ |
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*/ |
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example_kset = kset_create_and_add("kset_example", NULL, kernel_kobj); |
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if (!example_kset) |
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return -ENOMEM; |
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/* |
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* Create three objects and register them with our kset |
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*/ |
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foo_obj = create_foo_obj("foo"); |
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if (!foo_obj) |
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goto foo_error; |
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bar_obj = create_foo_obj("bar"); |
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if (!bar_obj) |
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goto bar_error; |
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baz_obj = create_foo_obj("baz"); |
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if (!baz_obj) |
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goto baz_error; |
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return 0; |
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baz_error: |
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destroy_foo_obj(bar_obj); |
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bar_error: |
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destroy_foo_obj(foo_obj); |
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foo_error: |
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kset_unregister(example_kset); |
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return -EINVAL; |
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} |
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static void __exit example_exit(void) |
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{ |
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destroy_foo_obj(baz_obj); |
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destroy_foo_obj(bar_obj); |
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destroy_foo_obj(foo_obj); |
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kset_unregister(example_kset); |
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} |
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module_init(example_init); |
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module_exit(example_exit); |
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MODULE_LICENSE("GPL v2"); |
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MODULE_AUTHOR("Greg Kroah-Hartman <[email protected]>");
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