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4. configfs_macros.h

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * configfs_macros.h - extends macros for configfs
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 *
 * Based on sysfs:
 * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
 *
 * Based on kobject.h:
 *      Copyright (c) 2002-2003	Patrick Mochel
 *      Copyright (c) 2002-2003	Open Source Development Labs
 *
 * configfs Copyright (C) 2005 Oracle.  All rights reserved.
 *
 * Added CONFIGFS_EATTR() macros from original configfs.h macros
 * Copright (C) 2008-2009 Nicholas A. Bellinger <nab@linux-iscsi.org>
 *
 * Please read Documentation/filesystems/configfs.txt before using the
 * configfs interface, ESPECIALLY the parts about reference counts and
 * item destructors.
 */

#ifndef _CONFIGFS_MACROS_H_
#define _CONFIGFS_MACROS_H_

#include <linux/configfs.h>

/*
 * Users often need to create attribute structures for their configurable
 * attributes, containing a configfs_attribute member and function pointers
 * for the show() and store() operations on that attribute. If they don't
 * need anything else on the extended attribute structure, they can use
 * this macro to define it.  The argument _name isends up as
 * 'struct _name_attribute, as well as names of to CONFIGFS_ATTR_OPS() below.
 * The argument _item is the name of the structure containing the
 * struct config_item or struct config_group structure members
 */
#define CONFIGFS_EATTR_STRUCT(_name, _item)				\
struct _name##_attribute {						\
	struct configfs_attribute attr;					\
	ssize_t (*show)(struct _item *, char *);			\
	ssize_t (*store)(struct _item *, const char *, size_t);		\
}

/*
 * With the extended attribute structure, users can use this macro
 * (similar to sysfs' __ATTR) to make defining attributes easier.
 * An example:
 * #define MYITEM_EATTR(_name, _mode, _show, _store)	\
 * struct myitem_attribute childless_attr_##_name =	\
 *         __CONFIGFS_EATTR(_name, _mode, _show, _store)
 */
#define __CONFIGFS_EATTR(_name, _mode, _show, _store)			\
{									\
	.attr	= {							\
			.ca_name = __stringify(_name),			\
			.ca_mode = _mode,				\
			.ca_owner = THIS_MODULE,			\
	},								\
	.show	= _show,						\
	.store	= _store,						\
}
/* Here is a readonly version, only requiring a show() operation */
#define __CONFIGFS_EATTR_RO(_name, _show)				\
{									\
	.attr	= {							\
			.ca_name = __stringify(_name),			\
			.ca_mode = 0444,				\
			.ca_owner = THIS_MODULE,			\
	},								\
	.show	= _show,						\
}

/*
 * With these extended attributes, the simple show_attribute() and
 * store_attribute() operations need to call the show() and store() of the
 * attributes.  This is a common pattern, so we provide a macro to define
 * them.  The argument _name is the name of the attribute defined by
 * CONFIGFS_ATTR_STRUCT(). The argument _item is the name of the structure
 * containing the struct config_item or struct config_group structure member.
 * The argument _item_member is the actual name of the struct config_* struct
 * in your _item structure.  Meaning  my_structure->some_config_group.
 *		                      ^^_item^^^^^  ^^_item_member^^^
 * This macro expects the attributes to be named "struct <name>_attribute".
 */
#define CONFIGFS_EATTR_OPS_TO_FUNC(_name, _item, _item_member)		\
static struct _item *to_##_name(struct config_item *ci)			\
{									\
	return (ci) ? container_of(to_config_group(ci), struct _item,	\
		_item_member) : NULL;					\
}

#define CONFIGFS_EATTR_OPS_SHOW(_name, _item)				\
static ssize_t _name##_attr_show(struct config_item *item,		\
				 struct configfs_attribute *attr,	\
				 char *page)				\
{									\
	struct _item *_item = to_##_name(item);				\
	struct _name##_attribute * _name##_attr =			\
		container_of(attr, struct _name##_attribute, attr);	\
	ssize_t ret = 0;						\
									\
	if (_name##_attr->show)						\
		ret = _name##_attr->show(_item, page);			\
	return ret;							\
}

#define CONFIGFS_EATTR_OPS_STORE(_name, _item)				\
static ssize_t _name##_attr_store(struct config_item *item,		\
				  struct configfs_attribute *attr,	\
				  const char *page, size_t count)	\
{									\
	struct _item *_item = to_##_name(item);				\
	struct _name##_attribute * _name##_attr =			\
		container_of(attr, struct _name##_attribute, attr);	\
	ssize_t ret = -EINVAL;						\
									\
	if (_name##_attr->store)					\
		ret = _name##_attr->store(_item, page, count);		\
	return ret;							\
}

#define CONFIGFS_EATTR_OPS(_name, _item, _item_member)			\
	CONFIGFS_EATTR_OPS_TO_FUNC(_name, _item, _item_member);		\
	CONFIGFS_EATTR_OPS_SHOW(_name, _item);				\
	CONFIGFS_EATTR_OPS_STORE(_name, _item);

#define CONFIGFS_EATTR_OPS_RO(_name, _item, _item_member)		\
	CONFIGFS_EATTR_OPS_TO_FUNC(_name, _item, _item_member);		\
	CONFIGFS_EATTR_OPS_SHOW(_name, _item);

#endif /* _CONFIGFS_MACROS_H_ */