configfs: implement binary attributes

ConfigFS lacked binary attributes up until now. This patch
introduces support for binary attributes in a somewhat similar
manner of sysfs binary attributes albeit with changes that
fit the configfs usage model.

Problems that configfs binary attributes fix are everything that
requires a binary blob as part of the configuration of a resource,
such as bitstream loading for FPGAs, DTBs for dynamically created
devices etc.

Look at Documentation/filesystems/configfs/configfs.txt for internals
and howto use them.

This patch is against linux-next as of today that contains
Christoph's configfs rework.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
[hch: folded a fix from Geert Uytterhoeven <geert+renesas@glider.be>]
[hch: a few tiny updates based on review feedback]
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 50 insertions, 0 deletions

diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index 758a029..f7300d0 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -51,6 +51,7 @@ struct module;
 struct configfs_item_operations;
 struct configfs_group_operations;
 struct configfs_attribute;
+struct configfs_bin_attribute;
 struct configfs_subsystem;
 
 struct config_item {
@@ -84,6 +85,7 @@ struct config_item_type {
 	struct configfs_item_operations		*ct_item_ops;
 	struct configfs_group_operations	*ct_group_ops;
 	struct configfs_attribute		**ct_attrs;
+	struct configfs_bin_attribute		**ct_bin_attrs;
 };
 
 /**
@@ -154,6 +156,54 @@ static struct configfs_attribute _pfx##attr_##_name = {	\
 	.store		= _pfx##_name##_store,		\
 }
 
+struct file;
+struct vm_area_struct;
+
+struct configfs_bin_attribute {
+	struct configfs_attribute cb_attr;	/* std. attribute */
+	void *cb_private;			/* for user       */
+	size_t cb_max_size;			/* max core size  */
+	ssize_t (*read)(struct config_item *, void *, size_t);
+	ssize_t (*write)(struct config_item *, const void *, size_t);
+};
+
+#define CONFIGFS_BIN_ATTR(_pfx, _name, _priv, _maxsz)		\
+static struct configfs_bin_attribute _pfx##attr_##_name = {	\
+	.cb_attr = {						\
+		.ca_name	= __stringify(_name),		\
+		.ca_mode	= S_IRUGO | S_IWUSR,		\
+		.ca_owner	= THIS_MODULE,			\
+	},							\
+	.cb_private	= _priv,				\
+	.cb_max_size	= _maxsz,				\
+	.read		= _pfx##_name##_read,			\
+	.write		= _pfx##_name##_write,			\
+}
+
+#define CONFIGFS_BIN_ATTR_RO(_pfx, _name, _priv, _maxsz)	\
+static struct configfs_attribute _pfx##attr_##_name = {		\
+	.cb_attr = {						\
+		.ca_name	= __stringify(_name),		\
+		.ca_mode	= S_IRUGO,			\
+		.ca_owner	= THIS_MODULE,			\
+	},							\
+	.cb_private	= _priv,				\
+	.cb_max_size	= _maxsz,				\
+	.read		= _pfx##_name##_read,			\
+}
+
+#define CONFIGFS_BIN_ATTR_WO(_pfx, _name, _priv, _maxsz)	\
+static struct configfs_attribute _pfx##attr_##_name = {		\
+	.cb_attr = {						\
+		.ca_name	= __stringify(_name),		\
+		.ca_mode	= S_IWUSR,			\
+		.ca_owner	= THIS_MODULE,			\
+	},							\
+	.cb_private	= _priv,				\
+	.cb_max_size	= _maxsz,				\
+	.write		= _pfx##_name##_write,			\
+}
+
 /*
  * If allow_link() exists, the item can symlink(2) out to other
  * items.  If the item is a group, it may support mkdir(2).