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samples/kobject: constify 'struct foo_attribute'

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

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://patch.msgid.link/20251029-sysfs-const-attr-prep-v5-6-ea7d745acff4@weissschuh.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Thomas Weißschuh
2025-10-29 09:12:15 +01:00
committed by Greg Kroah-Hartman
parent c301a2e2d7
commit 2d76fdc1c9
1 changed files with 17 additions and 16 deletions
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33
samples/kobject/kset-example.c
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@@ -37,10 +37,11 @@ struct foo_obj {
/* a custom attribute that works just for a struct foo_obj. */ /* a custom attribute that works just for a struct foo_obj. */
struct foo_attribute { struct foo_attribute {
struct attribute attr; struct attribute attr;
ssize_t (*show)(struct foo_obj *foo, struct foo_attribute *attr, char *buf); ssize_t (*show)(struct foo_obj *foo, const 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 (*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 * 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, struct attribute *attr,
char *buf) char *buf)
{ {
struct foo_attribute *attribute; const struct foo_attribute *attribute;
struct foo_obj *foo; struct foo_obj *foo;
attribute = to_foo_attr(attr); attribute = to_foo_attr(attr);
@@ -73,7 +74,7 @@ static ssize_t foo_attr_store(struct kobject *kobj,
struct attribute *attr, struct attribute *attr,
const char *buf, size_t len) const char *buf, size_t len)
{ {
struct foo_attribute *attribute; const struct foo_attribute *attribute;
struct foo_obj *foo; struct foo_obj *foo;
attribute = to_foo_attr(attr); 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. * 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) char *buf)
{ {
return sysfs_emit(buf, "%d\n", foo_obj->foo); 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) const char *buf, size_t count)
{ {
int ret; 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. */ /* 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); __ATTR(foo, 0664, foo_show, foo_store);
/* /*
* More complex function where we determine which variable is being accessed by * More complex function where we determine which variable is being accessed by
* looking at the attribute for the "baz" and "bar" files. * 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) char *buf)
{ {
int var; 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); 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) const char *buf, size_t count)
{ {
int var, ret; int var, ret;
@@ -163,16 +164,16 @@ static ssize_t b_store(struct foo_obj *foo_obj, struct foo_attribute *attr,
return count; return count;
} }
static struct foo_attribute baz_attribute = static const struct foo_attribute baz_attribute =
__ATTR(baz, 0664, b_show, b_store); __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); __ATTR(bar, 0664, b_show, b_store);
/* /*
* Create a group of attributes so that we can create and destroy them all * Create a group of attributes so that we can create and destroy them all
* at once. * at once.
*/ */
static struct attribute *foo_default_attrs[] = { static const struct attribute *const foo_default_attrs[] = {
&foo_attribute.attr, &foo_attribute.attr,
&baz_attribute.attr, &baz_attribute.attr,
&bar_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, static umode_t foo_default_attrs_is_visible(struct kobject *kobj,
struct attribute *attr, const struct attribute *attr,
int n) int n)
{ {
/* Hide attributes with the same name as the kobject. */ /* 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 = { static const struct attribute_group foo_default_group = {
.attrs = foo_default_attrs, .attrs_const = foo_default_attrs,
.is_visible = foo_default_attrs_is_visible, .is_visible_const = foo_default_attrs_is_visible,
}; };
__ATTRIBUTE_GROUPS(foo_default); __ATTRIBUTE_GROUPS(foo_default);