[PATCH mtd-www] doc/ubi.xml: clarify from the start that block device on UBI is read-only

[Thomas Petazzoni]

In the introduction, the sentence that introduces ubiblock might let
one think that any read/write block filesystem can be used on top of
UBI, which is wrong. So clarify from the start that this is read-only.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni at bootlin.com>
---
 doc/ubi.xml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/doc/ubi.xml b/doc/ubi.xml
index 1290735..21bbd00 100644
--- a/doc/ubi.xml
+++ b/doc/ubi.xml
@@ -184,9 +184,9 @@ similar because:</p>
 	mechanisms).</li>
 </ul>
 
-<p>UBI also provides a block device that allows regular, block-oriented
-file systems to be mounted on top of an UBI volume. This is possible because UBI
-handles bad-blocks transparently.</p>
+<p>UBI also provides a read-only block device that allows regular, block-oriented
+file systems to be mounted on top of an UBI volume, but only for read-only
+operation. This is possible because UBI handles bad-blocks transparently.</p>
 
 <p>There is an additional driver called <code>gluebi</code> which emulates MTD
 devices on top of UBI volumes. This looks a little strange, because UBI works
-- 
2.55.0