OpenCloudOS-Kernel/samples/kobject/kset-example.c

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// SPDX-License-Identifier: GPL-2.0
/*
* Sample kset and ktype 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 cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-24 16:04:11 +08:00
#include <linux/slab.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 const 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 sysfs_emit(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)
{
int ret;
ret = kstrtoint(buf, 10, &foo_obj->foo);
if (ret < 0)
return ret;
return count;
}
/* Sysfs attributes cannot be world-writable. */
static struct foo_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 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 sysfs_emit(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, ret;
ret = kstrtoint(buf, 10, &var);
if (ret < 0)
return ret;
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, 0664, b_show, b_store);
static struct foo_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 *foo_default_attrs[] = {
&foo_attribute.attr,
&baz_attribute.attr,
&bar_attribute.attr,
NULL, /* need to NULL terminate the list of attributes */
};
ATTRIBUTE_GROUPS(foo_default);
/*
* 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_groups = foo_default_groups,
};
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) {
kobject_put(&foo->kobj);
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 __init 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:
kset_unregister(example_kset);
return -EINVAL;
}
static void __exit 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 v2");
MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>");