mtd: part: Create the master device node when partitioned

For many use cases, it helps to have a device node for the entire
MTD device as well as device nodes for the individual partitions.
For example, this allows querying the entire device's properties.
A common idiom is to create an additional partition which spans
over the whole device.

This patch makes a config option, CONFIG_MTD_PARTITIONED_MASTER,
which makes the master partition present even when the device is
partitioned. This isn't turned on by default since it presents
a backwards-incompatible device numbering.

The patch also makes the parent of a partition device be the master,
if the config flag is set, now that the master is a full device.

Signed-off-by: Dan Ehrenberg <dehrenberg@chromium.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/mtd/Kconfig b/drivers/mtd/Kconfig
index 71fea895ce38..a03ad2951c7b 100644
--- a/drivers/mtd/Kconfig
+++ b/drivers/mtd/Kconfig
@@ -309,6 +309,19 @@ config MTD_SWAP
           The driver provides wear leveling by storing erase counter into the
           OOB.
 
+config MTD_PARTITIONED_MASTER
+        bool "Retain master device when partitioned"
+        default n
+        depends on MTD
+        help
+          For historical reasons, by default, either a master is present or
+          several partitions are present, but not both. The concern was that
+          data listed in multiple partitions was dangerous; however, SCSI does
+          this and it is frequently useful for applications. This config option
+          leaves the master in even if the device is partitioned. It also makes
+          the parent of the partition device be the master device, rather than
+          what lies behind the master.
+
 source "drivers/mtd/chips/Kconfig"
 
 source "drivers/mtd/maps/Kconfig"