Commit 2d76fdc1 authored by Thomas Weißschuh's avatar Thomas Weißschuh Committed by Greg Kroah-Hartman
Browse files

samples/kobject: constify 'struct foo_attribute' 



Showcase and test the new 'struct attribute' constification facilities.

Signed-off-by: default avatarThomas Weißschuh <linux@weissschuh.net>
Link: https://patch.msgid.link/20251029-sysfs-const-attr-prep-v5-6-ea7d745acff4@weissschuh.net


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent c301a2e2

samples/kobject/kset-example.c

+17 −16
Original line number Diff line number Diff line
@@ -37,10 +37,11 @@ struct foo_obj { 
/* 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);

	ssize_t (*show)(struct foo_obj *foo, const struct foo_attribute *attr, char *buf);

	ssize_t (*store)(struct foo_obj *foo, const struct foo_attribute *attr,

			 const char *buf, size_t count);

};

#define to_foo_attr(x) container_of(x, struct foo_attribute, attr)

#define to_foo_attr(x) container_of_const(x, struct foo_attribute, attr)



/*

 * The default show function that must be passed to sysfs.  This will be
@@ -53,7 +54,7 @@ static ssize_t foo_attr_show(struct kobject *kobj, 
			     struct attribute *attr,

			     char *buf)

{

	struct foo_attribute *attribute;

	const struct foo_attribute *attribute;

	struct foo_obj *foo;



	attribute = to_foo_attr(attr);
@@ -73,7 +74,7 @@ static ssize_t foo_attr_store(struct kobject *kobj, 
			      struct attribute *attr,

			      const char *buf, size_t len)

{

	struct foo_attribute *attribute;

	const struct foo_attribute *attribute;

	struct foo_obj *foo;



	attribute = to_foo_attr(attr);
@@ -109,13 +110,13 @@ static void foo_release(struct kobject *kobj) 
/*

 * 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,

static ssize_t foo_show(struct foo_obj *foo_obj, const 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,

static ssize_t foo_store(struct foo_obj *foo_obj, const struct foo_attribute *attr,

			 const char *buf, size_t count)

{

	int ret;
@@ -128,14 +129,14 @@ static ssize_t foo_store(struct foo_obj *foo_obj, struct foo_attribute *attr, 
}



/* Sysfs attributes cannot be world-writable. */

static struct foo_attribute foo_attribute =

static const 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,

static ssize_t b_show(struct foo_obj *foo_obj, const struct foo_attribute *attr,

		      char *buf)

{

	int var;
@@ -147,7 +148,7 @@ static ssize_t b_show(struct foo_obj *foo_obj, struct foo_attribute *attr, 
	return sysfs_emit(buf, "%d\n", var);

}



static ssize_t b_store(struct foo_obj *foo_obj, struct foo_attribute *attr,

static ssize_t b_store(struct foo_obj *foo_obj, const struct foo_attribute *attr,

		       const char *buf, size_t count)

{

	int var, ret;
@@ -163,16 +164,16 @@ static ssize_t b_store(struct foo_obj *foo_obj, struct foo_attribute *attr, 
	return count;

}



static struct foo_attribute baz_attribute =

static const struct foo_attribute baz_attribute =

	__ATTR(baz, 0664, b_show, b_store);

static struct foo_attribute bar_attribute =

static const 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[] = {

static const struct attribute *const foo_default_attrs[] = {

	&foo_attribute.attr,

	&baz_attribute.attr,

	&bar_attribute.attr,
@@ -180,7 +181,7 @@ static struct attribute *foo_default_attrs[] = { 
};



static umode_t foo_default_attrs_is_visible(struct kobject *kobj,

					    struct attribute *attr,

					    const struct attribute *attr,

					    int n)

{

	/* Hide attributes with the same name as the kobject. */
@@ -190,8 +191,8 @@ static umode_t foo_default_attrs_is_visible(struct kobject *kobj, 
}



static const struct attribute_group foo_default_group = {

	.attrs		= foo_default_attrs,

	.is_visible	= foo_default_attrs_is_visible,

	.attrs_const		= foo_default_attrs,

	.is_visible_const	= foo_default_attrs_is_visible,

};

__ATTRIBUTE_GROUPS(foo_default);