summaryrefslogtreecommitdiffstats
path: root/samples/kobject/kobject-example.c
diff options
context:
space:
mode:
authorRosen Penev <rosenp@gmail.com>2026-09-27 13:35:01 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2026-10-01 11:04:53 +0200
commit8167c1f071426706c233e93ecfd13aba7d5c06c8 (patch)
tree2c0cd5f5e1cc35eadee98d49fe034f96a88856ce /samples/kobject/kobject-example.c
downloadlinux-stable-8167c1f071426706c233e93ecfd13aba7d5c06c8.tar.gz
linux-stable-8167c1f071426706c233e93ecfd13aba7d5c06c8.zip
tty: serial: mpc52xx_uart: move static declarations up.grafted
Avoid a compilation error so that they're not used before being declared. Fixes: 4d105880666a ("tty: serial: mpc52xx_uart: add bounds check for psc_num array index") Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202609260356.tJWbd1WU-lkp@intel.com/ Signed-off-by: Rosen Penev <rosenp@gmail.com> Link: https://patch.msgid.link/20260927203501.14105-1-rosenp@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'samples/kobject/kobject-example.c')
-rw-r--r--samples/kobject/kobject-example.c145
1 files changed, 145 insertions, 0 deletions
diff --git a/samples/kobject/kobject-example.c b/samples/kobject/kobject-example.c
new file mode 100644
index 000000000..36f3fbc47
--- /dev/null
+++ b/samples/kobject/kobject-example.c
@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Sample kobject 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 <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, const struct kobj_attribute *attr,
+ char *buf)
+{
+ return sysfs_emit(buf, "%d\n", foo);
+}
+
+static ssize_t foo_store(struct kobject *kobj, const struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int ret;
+
+ ret = kstrtoint(buf, 10, &foo);
+ if (ret < 0)
+ return ret;
+
+ return count;
+}
+
+/* Sysfs attributes cannot be world-writable. */
+static const struct kobj_attribute foo_attribute =
+ __KOBJ_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 kobject *kobj, const struct kobj_attribute *attr,
+ char *buf)
+{
+ int var;
+
+ if (strcmp(attr->attr.name, "baz") == 0)
+ var = baz;
+ else
+ var = bar;
+ return sysfs_emit(buf, "%d\n", var);
+}
+
+static ssize_t b_store(struct kobject *kobj, const struct kobj_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)
+ baz = var;
+ else
+ bar = var;
+ return count;
+}
+
+static const struct kobj_attribute baz_attribute =
+ __KOBJ_ATTR(baz, 0664, b_show, b_store);
+static const struct kobj_attribute bar_attribute =
+ __KOBJ_ATTR(bar, 0664, b_show, b_store);
+
+
+/*
+ * Create a group of attributes so that we can create and destroy them all
+ * at once.
+ */
+static const struct attribute *const 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 const struct attribute_group attr_group = {
+ .attrs_const = attrs,
+};
+
+static struct kobject *example_kobj;
+
+static int __init 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 __exit example_exit(void)
+{
+ kobject_put(example_kobj);
+}
+
+module_init(example_init);
+module_exit(example_exit);
+MODULE_DESCRIPTION("Sample kobject implementation");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>");