From 44bfe16e1083d66f97a5289e359c52ee2c8b19a7 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Tue, 27 Nov 2007 11:28:26 -0800 Subject: kobject: add sample code for how to use ksets/ktypes/kobjects This is a more complex example showing how to create a kset and a ktype and some default attributes for a group of kobjects. Cc: Kay Sievers Signed-off-by: Greg Kroah-Hartman --- samples/kobject/kset-example.c | 278 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 278 insertions(+) create mode 100644 samples/kobject/kset-example.c (limited to 'samples/kobject/kset-example.c') diff --git a/samples/kobject/kset-example.c b/samples/kobject/kset-example.c new file mode 100644 index 000000000000..b0a1b4fe6584 --- /dev/null +++ b/samples/kobject/kset-example.c @@ -0,0 +1,278 @@ +/* + * Sample kset and ktype implementation + * + * Copyright (C) 2004-2007 Greg Kroah-Hartman + * Copyright (C) 2007 Novell Inc. + * + * Released under the GPL version 2 only. + * + */ +#include +#include +#include +#include +#include + +/* + * This module shows how to create a kset in sysfs called + * /sys/kernel/kset-example + * Then tree kobjects are created and assigned to this kset, "foo", "baz", + * and "bar". In those kobjects, attributes of the same name are also + * created and if an integer is written to these files, it can be later + * read out of it. + */ + + +/* + * This is our "object" that we will create a few of and register them with + * sysfs. + */ +struct foo_obj { + struct kobject kobj; + int foo; + int baz; + int bar; +}; +#define to_foo_obj(x) container_of(x, struct foo_obj, kobj) + +/* a custom attribute that works just for a struct foo_obj. */ +struct foo_attribute { + struct attribute attr; + ssize_t (*show)(struct foo_obj *foo, struct foo_attribute *attr, char *buf); + ssize_t (*store)(struct foo_obj *foo, struct foo_attribute *attr, const char *buf, size_t count); +}; +#define to_foo_attr(x) container_of(x, struct foo_attribute, attr) + +/* + * The default show function that must be passed to sysfs. This will be + * called by sysfs for whenever a show function is called by the user on a + * sysfs file associated with the kobjects we have registered. We need to + * transpose back from a "default" kobject to our custom struct foo_obj and + * then call the show function for that specific object. + */ +static ssize_t foo_attr_show(struct kobject *kobj, + struct attribute *attr, + char *buf) +{ + struct foo_attribute *attribute; + struct foo_obj *foo; + + attribute = to_foo_attr(attr); + foo = to_foo_obj(kobj); + + if (!attribute->show) + return -EIO; + + return attribute->show(foo, attribute, buf); +} + +/* + * Just like the default show function above, but this one is for when the + * sysfs "store" is requested (when a value is written to a file.) + */ +static ssize_t foo_attr_store(struct kobject *kobj, + struct attribute *attr, + const char *buf, size_t len) +{ + struct foo_attribute *attribute; + struct foo_obj *foo; + + attribute = to_foo_attr(attr); + foo = to_foo_obj(kobj); + + if (!attribute->store) + return -EIO; + + return attribute->store(foo, attribute, buf, len); +} + +/* Our custom sysfs_ops that we will associate with our ktype later on */ +static struct sysfs_ops foo_sysfs_ops = { + .show = foo_attr_show, + .store = foo_attr_store, +}; + +/* + * The release function for our object. This is REQUIRED by the kernel to + * have. We free the memory held in our object here. + * + * NEVER try to get away with just a "blank" release function to try to be + * smarter than the kernel. Turns out, no one ever is... + */ +static void foo_release(struct kobject *kobj) +{ + struct foo_obj *foo; + + foo = to_foo_obj(kobj); + kfree(foo); +} + +/* + * The "foo" file where the .foo variable is read from and written to. + */ +static ssize_t foo_show(struct foo_obj *foo_obj, struct foo_attribute *attr, + char *buf) +{ + return sprintf(buf, "%d\n", foo_obj->foo); +} + +static ssize_t foo_store(struct foo_obj *foo_obj, struct foo_attribute *attr, + const char *buf, size_t count) +{ + sscanf(buf, "%du", &foo_obj->foo); + return count; +} + +static struct foo_attribute foo_attribute = + __ATTR(foo, 0666, foo_show, foo_store); + +/* + * More complex function where we determine which varible is being accessed by + * looking at the attribute for the "baz" and "bar" files. + */ +static ssize_t b_show(struct foo_obj *foo_obj, struct foo_attribute *attr, + char *buf) +{ + int var; + + if (strcmp(attr->attr.name, "baz") == 0) + var = foo_obj->baz; + else + var = foo_obj->bar; + return sprintf(buf, "%d\n", var); +} + +static ssize_t b_store(struct foo_obj *foo_obj, struct foo_attribute *attr, + const char *buf, size_t count) +{ + int var; + + sscanf(buf, "%du", &var); + if (strcmp(attr->attr.name, "baz") == 0) + foo_obj->baz = var; + else + foo_obj->bar = var; + return count; +} + +static struct foo_attribute baz_attribute = + __ATTR(baz, 0666, b_show, b_store); +static struct foo_attribute bar_attribute = + __ATTR(bar, 0666, b_show, b_store); + +/* + * Create a group of attributes so that we can create and destory them all + * at once. + */ +static struct attribute *foo_default_attrs[] = { + &foo_attribute.attr, + &baz_attribute.attr, + &bar_attribute.attr, + NULL, /* need to NULL terminate the list of attributes */ +}; + +/* + * Our own ktype for our kobjects. Here we specify our sysfs ops, the + * release function, and the set of default attributes we want created + * whenever a kobject of this type is registered with the kernel. + */ +static struct kobj_type foo_ktype = { + .sysfs_ops = &foo_sysfs_ops, + .release = foo_release, + .default_attrs = foo_default_attrs, +}; + +static struct kset *example_kset; +static struct foo_obj *foo_obj; +static struct foo_obj *bar_obj; +static struct foo_obj *baz_obj; + +static struct foo_obj *create_foo_obj(const char *name) +{ + struct foo_obj *foo; + int retval; + + /* allocate the memory for the whole object */ + foo = kzalloc(sizeof(*foo), GFP_KERNEL); + if (!foo) + return NULL; + + /* + * As we have a kset for this kobject, we need to set it before calling + * the kobject core. + */ + foo->kobj.kset = example_kset; + + /* + * Initialize and add the kobject to the kernel. All the default files + * will be created here. As we have already specified a kset for this + * kobject, we don't have to set a parent for the kobject, the kobject + * will be placed beneath that kset automatically. + */ + retval = kobject_init_and_add(&foo->kobj, &foo_ktype, NULL, "%s", name); + if (retval) { + kfree(foo); + return NULL; + } + + /* + * We are always responsible for sending the uevent that the kobject + * was added to the system. + */ + kobject_uevent(&foo->kobj, KOBJ_ADD); + + return foo; +} + +static void destroy_foo_obj(struct foo_obj *foo) +{ + kobject_put(&foo->kobj); +} + +static int example_init(void) +{ + /* + * Create a kset with the name of "kset_example", + * located under /sys/kernel/ + */ + example_kset = kset_create_and_add("kset_example", NULL, kernel_kobj); + if (!example_kset) + return -ENOMEM; + + /* + * Create three objects and register them with our kset + */ + foo_obj = create_foo_obj("foo"); + if (!foo_obj) + goto foo_error; + + bar_obj = create_foo_obj("bar"); + if (!bar_obj) + goto bar_error; + + baz_obj = create_foo_obj("baz"); + if (!baz_obj) + goto baz_error; + + return 0; + +baz_error: + destroy_foo_obj(bar_obj); +bar_error: + destroy_foo_obj(foo_obj); +foo_error: + return -EINVAL; +} + +static void example_exit(void) +{ + destroy_foo_obj(baz_obj); + destroy_foo_obj(bar_obj); + destroy_foo_obj(foo_obj); + kset_unregister(example_kset); +} + +module_init(example_init); +module_exit(example_exit); +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Greg Kroah-Hartman "); -- cgit v1.2.3-59-g8ed1b