Messages in this thread | | | Date | Tue, 27 Nov 2007 15:04:06 -0800 | From | Greg KH <> | Subject | [RFC] Sample kset/ktype/kobject implementation |
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/* * Sample kset and ktype implementation * * Copyright (C) 2004-2007 Greg Kroah-Hartman <greg@kroah.com> * Copyright (C) 2007 Novell Inc. * * Released under the GPL version 2 only. * */ #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 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;
/* initialize the kobject portion of the object properly */ kobject_set_name(&foo->kobj, "%s", name); foo->kobj.kset = example_kset; foo->kobj.ktype = &foo_ktype;
/* * Register the kobject with the kernel, all the default files will * be created here and the uevent will be sent out. If we were to * call kobject_init() and then kobject_add() we would be * responsible for sending out the initial KOBJ_ADD uevent. */ retval = kobject_register(&foo->kobj); if (retval) { kfree(foo); return NULL; }
return foo; }
static void destroy_foo_obj(struct foo_obj *foo) { kobject_unregister(&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_register("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 <greg@kroah.com>"); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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