UBI: add UBI control device

This patch is a preparation to make UBI devices dynamic. It
adds an UBI control device which has dynamically allocated
major number and registers itself as "ubi_ctrl". It does not
do anything so far. The idea is that this device will allow
to attach/detach MTD devices from userspace.

This is symilar to what the Linux device mapper has.

The next things to do are:
* Fix UBI, because it now assumes UBI devices cannot go away
* Implement control device ioctls which will attach/detach MTD
  devices

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/cdev.c b/drivers/mtd/ubi/cdev.c
index 22c15a388f28..bc900d24cdba 100644
--- a/drivers/mtd/ubi/cdev.c
+++ b/drivers/mtd/ubi/cdev.c
@@ -28,6 +28,11 @@
  *
  * Major and minor numbers are assigned dynamically to both UBI and volume
  * character devices.
+ *
+ * Well, there is the third kind of character devices - the UBI control
+ * character device, which allows to manipulate by UBI devices - create and
+ * delete them. In other words, it is used for attaching and detaching MTD
+ * devices.
  */
 
 #include <linux/module.h>
@@ -693,6 +698,11 @@ static int ubi_cdev_ioctl(struct inode *inode, struct file *file,
         return err;
 }
 
+/* UBI control character device operations */
+struct file_operations ubi_ctrl_cdev_operations = {
+        .owner = THIS_MODULE,
+};
+
 /* UBI character device operations */
 struct file_operations ubi_cdev_operations = {
         .owner = THIS_MODULE,