Linux-2.6设备模型与sysfs文件系统
kobject对象：
它是设备模型的基本结构，对应于sysfs文件系统中的一个目录，它是一个结构体，不过在Linux中引入了面向对象的思想，从某些角度，也可以看成是一个类。kobject对象通常被嵌入到其他的结构中，从面向对象的观点看，kobject可以看成是基类，而其他类都是派生的产物。
| 一个kobject的例子 |
| /* * Sample kobject implementation * * Copyright (C) 2004-2007 Greg Kroah-Hartman <[email protected]> * 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 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 sprintf(buf, "%d\n", foo); }
static ssize_t foo_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { sscanf(buf, "%du", &foo); return count; }
static struct kobj_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 kobject *kobj, struct kobj_attribute *attr, char *buf) { int var;
if (strcmp(attr->attr.name, "baz") == 0) var = baz; else var = bar; return sprintf(buf, "%d\n", var); }
static ssize_t b_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { int var;
sscanf(buf, "%du", &var); if (strcmp(attr->attr.name, "baz") == 0) baz = var; else bar = var; return count; }
static struct kobj_attribute baz_attribute = __ATTR(baz, 0666, b_show, b_store); static struct kobj_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 *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 struct attribute_group attr_group = { .attrs = attrs, };
static struct kobject *example_kobj;
static int 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 example_exit(void) { kobject_put(example_kobj); }
module_init(example_init); module_exit(example_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Greg Kroah-Hartman <[email protected]>"); |
该程序在/sys/kernel/下创建了一个目录，名为kobject-example, 在kobject-example目录下分别对应了三个文件bar, baz, foo, 分别对应着三个变量。
kset：
kobject通常通过kset组织成层次化的结构，kset是具有相同类型的kobject的集合，在内核中用kset数据结构表示。
| kset例子 |
| /* * Sample kset and ktype implementation * * Copyright (C) 2004-2007 Greg Kroah-Hartman <[email protected]> * 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;
/* * 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 <[email protected]>"); |
该程序在/sys/kernel/下创建了一个目录，名为kset-example, 在kset-example目录下分别对应了三个子目录bar, baz, foo, 里面又有三个文件 ，分别对应着三个变量。