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Subject[PATCH 1/3] add a private data field within kobj_attribute structure (final#2)
[PATCH 1/3] add a private data field within kobj_attribute structure.

This patch add a private data field, declared as void *, within kobj_attribute
structure. The _show() and _store() method in the sysfs attribute entries can
refer this information to identify what entry is accessed.
It makes easier to share a single method implementation with several similar
entries, like ones to export the list of capabilities the running kernel
supports.

Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
--
Documentation/kobject.txt | 6 ++++++
include/linux/kobject.h | 1 +
include/linux/sysfs.h | 7 +++++++
3 files changed, 14 insertions(+), 0 deletions(-)
diff --git a/Documentation/kobject.txt b/Documentation/kobject.txt
index bf3256e..efa5d71 100644
--- a/Documentation/kobject.txt
+++ b/Documentation/kobject.txt
@@ -207,6 +207,12 @@ Both types of attributes used here, with a kobject that has been created
with the kobject_create_and_add(), can be of type kobj_attribute, so no
special custom attribute is needed to be created.

+The simple kobj_attribute is prototyped at include/linux/kobject.h, and can
+contain your own show()/store() method and private data.
+When an attribute is accessed, these methods are invoked with kobject,
+kobj_attribute and read/write buffer. The method can refer the private data
+via given kobj_attribute, to show/store itself in the text representation.
+
See the example module, samples/kobject/kobject-example.c for an
implementation of a simple kobject and attributes.

diff --git a/include/linux/kobject.h b/include/linux/kobject.h
index caa3f41..57d5bf1 100644
--- a/include/linux/kobject.h
+++ b/include/linux/kobject.h
@@ -130,6 +130,7 @@ struct kobj_attribute {
char *buf);
ssize_t (*store)(struct kobject *kobj, struct kobj_attribute *attr,
const char *buf, size_t count);
+ void *data; /* a private field */
};

extern struct sysfs_ops kobj_sysfs_ops;
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 8027104..6f40ff9 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -50,6 +50,13 @@ struct attribute_group {
.store = _store, \
}

+#define __ATTR_DATA(_name,_mode,_show,_store,_data) { \
+ .attr = {.name = __stringify(_name), .mode = _mode }, \
+ .show = _show, \
+ .store = _store, \
+ .data = (void *)(_data), \
+}
+
#define __ATTR_RO(_name) { \
.attr = { .name = __stringify(_name), .mode = 0444 }, \
.show = _name##_show, \
--
OSS Platform Development Division, NEC
KaiGai Kohei <kaigai@ak.jp.nec.com>


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