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>
diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
index e779de3..a19ec5a 100644
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -30,6 +30,7 @@
#include <linux/mtd/mtd.h>
#include <linux/mtd/partitions.h>
#include <linux/err.h>
+#include <linux/kconfig.h>
#include "mtdcore.h"
@@ -379,10 +380,17 @@
slave->mtd.name = name;
slave->mtd.owner = master->owner;
- /* NOTE: we don't arrange MTDs as a tree; it'd be error-prone
- * to have the same data be in two different partitions.
+ /* NOTE: Historically, we didn't arrange MTDs as a tree out of
+ * concern for showing the same data in multiple partitions.
+ * However, it is very useful to have the master node present,
+ * so the MTD_PARTITIONED_MASTER option allows that. The master
+ * will have device nodes etc only if this is set, so make the
+ * parent conditional on that option. Note, this is a way to
+ * distinguish between the master and the partition in sysfs.
*/
- slave->mtd.dev.parent = master->dev.parent;
+ slave->mtd.dev.parent = IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER) ?
+ &master->dev :
+ master->dev.parent;
slave->mtd._read = part_read;
slave->mtd._write = part_write;
@@ -631,8 +639,8 @@
* and registers slave MTD objects which are bound to the master according to
* the partition definitions.
*
- * We don't register the master, or expect the caller to have done so,
- * for reasons of data integrity.
+ * For historical reasons, this function's caller only registers the master
+ * if the MTD_PARTITIONED_MASTER config option is set.
*/
int add_mtd_partitions(struct mtd_info *master,