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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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