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 63a36e89d0eb..85e9956a86de 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