bsg: Kconfig updates

- add the detailed explanation.
- remove 'default y'.
- make 'EXPERIMENTAL' keyword visible to the user in menu.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 9 insertions, 4 deletions

diff --git a/block/Kconfig b/block/Kconfig
index 6597b60e8e6..0768741d681 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -52,11 +52,16 @@ config LSF
 endif # BLOCK
 
 config BLK_DEV_BSG
-        bool "Block layer SG support"
+        bool "Block layer SG support v4 (EXPERIMENTAL)"
         depends on (SCSI=y) && EXPERIMENTAL
-        default y
         ---help---
-        Saying Y here will enable generic SG (SCSI generic) v4
-        support for any block device.
+        Saying Y here will enable generic SG (SCSI generic) v4 support
+        for any block device.
+
+        Unlike SG v3 (aka block/scsi_ioctl.c drivers/scsi/sg.c), SG v4
+        can handle complicated SCSI commands: tagged variable length cdbs
+        with bidirectional data transfers and generic request/response
+        protocols (e.g. Task Management Functions and SMP in Serial
+        Attached SCSI).
 
 source block/Kconfig.iosched