configfs: add show and store methods to struct configfs_attribute

Add methods to struct configfs_attribute to directly show and store
attributes without adding boilerplate code to every user.  In addition
to the methods this also adds 3 helper macros to define read/write,
read-only and write-only attributes with a single line of code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Nicholas Bellinger <nab@linux-iscsi.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 27 insertions, 0 deletions

diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index 63a36e8..85e9956 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -125,8 +125,35 @@ struct configfs_attribute {
 	const char		*ca_name;
 	struct module 		*ca_owner;
 	umode_t			ca_mode;
+	ssize_t (*show)(struct config_item *, char *);
+	ssize_t (*store)(struct config_item *, const char *, size_t);
 };
 
+#define CONFIGFS_ATTR(_pfx, _name)			\
+static struct configfs_attribute _pfx##attr_##_name = {	\
+	.ca_name	= __stringify(_name),		\
+	.ca_mode	= S_IRUGO | S_IWUSR,		\
+	.ca_owner	= THIS_MODULE,			\
+	.show		= _pfx##_name##_show,		\
+	.store		= _pfx##_name##_store,		\
+}
+
+#define CONFIGFS_ATTR_RO(_pfx, _name)			\
+static struct configfs_attribute _pfx##attr_##_name = {	\
+	.ca_name	= __stringify(_name),		\
+	.ca_mode	= S_IRUGO,			\
+	.ca_owner	= THIS_MODULE,			\
+	.show		= _pfx##_name##_show,		\
+}
+
+#define CONFIGFS_ATTR_WO(_pfx, _name)			\
+static struct configfs_attribute _pfx##attr_##_name = {	\
+	.ca_name	= __stringify(_name),		\
+	.ca_mode	= S_IWUSR,			\
+	.ca_owner	= THIS_MODULE,			\
+	.store		= _pfx##_name##_store,		\
+}
+
 /*
  * Users often need to create attribute structures for their configurable
  * attributes, containing a configfs_attribute member and function pointers