sysfs: Add sysfs_merge_group() and sysfs_unmerge_group()

This patch (as1420) adds sysfs_merge_group() and sysfs_unmerge_group()
functions, allowing drivers easily to add and remove sets of
attributes to a pre-existing attribute group directory.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 59 insertions, 0 deletions

diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c
index 23c1e598792a..442f34ff1af8 100644
--- a/fs/sysfs/group.c
+++ b/fs/sysfs/group.c
@@ -148,6 +148,65 @@ void sysfs_remove_group(struct kobject * kobj,
         sysfs_put(sd);
 }
 
+/**
+ * sysfs_merge_group - merge files into a pre-existing attribute group.
+ * @kobj:       The kobject containing the group.
+ * @grp:        The files to create and the attribute group they belong to.
+ *
+ * This function returns an error if the group doesn't exist or any of the
+ * files already exist in that group, in which case none of the new files
+ * are created.
+ */
+int sysfs_merge_group(struct kobject *kobj,
+                       const struct attribute_group *grp)
+{
+        struct sysfs_dirent *dir_sd;
+        int error = 0;
+        struct attribute *const *attr;
+        int i;
+
+        if (grp)
+                dir_sd = sysfs_get_dirent(kobj->sd, NULL, grp->name);
+        else
+                dir_sd = sysfs_get(kobj->sd);
+        if (!dir_sd)
+                return -ENOENT;
+
+        for ((i = 0, attr = grp->attrs); *attr && !error; (++i, ++attr))
+                error = sysfs_add_file(dir_sd, *attr, SYSFS_KOBJ_ATTR);
+        if (error) {
+                while (--i >= 0)
+                        sysfs_hash_and_remove(dir_sd, NULL, (*--attr)->name);
+        }
+        sysfs_put(dir_sd);
+
+        return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_merge_group);
+
+/**
+ * sysfs_unmerge_group - remove files from a pre-existing attribute group.
+ * @kobj:       The kobject containing the group.
+ * @grp:        The files to remove and the attribute group they belong to.
+ */
+void sysfs_unmerge_group(struct kobject *kobj,
+                       const struct attribute_group *grp)
+{
+        struct sysfs_dirent *dir_sd;
+        struct attribute *const *attr;
+
+        if (grp)
+                dir_sd = sysfs_get_dirent(kobj->sd, NULL, grp->name);
+        else
+                dir_sd = sysfs_get(kobj->sd);
+        if (dir_sd) {
+                for (attr = grp->attrs; *attr; ++attr)
+                        sysfs_hash_and_remove(dir_sd, NULL, (*attr)->name);
+                sysfs_put(dir_sd);
+        }
+}
+EXPORT_SYMBOL_GPL(sysfs_unmerge_group);
+
 
 EXPORT_SYMBOL_GPL(sysfs_create_group);
 EXPORT_SYMBOL_GPL(sysfs_update_group);