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 758a029011b1..f7300d023dbe 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).