sed-opal: add support flag for SUM in status ioctl

Not every OPAL drive supports SUM (Single User Mode), so report this
information to userspace via the get-status ioctl so that we can adjust
the formatting options accordingly.
Tested on a kingston drive (which supports it) and a samsung one
(which does not).

Signed-off-by: Luca Boccassi <bluca@debian.org>
Link: https://lore.kernel.org/r/20230210010612.28729-1-luca.boccassi@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/sed-opal.c

@@ -487,6 +487,8 @@ static int opal_discovery0_end(struct opal_dev *dev)
 			break;
 		case FC_SINGLEUSER:
 			single_user = check_sum(body->features);
+			if (single_user)
+				dev->flags |= OPAL_FL_SUM_SUPPORTED;
 			break;
 		case FC_GEOMETRY:
 			check_geometry(dev, body);

include/uapi/linux/sed-opal.h

@@ -144,6 +144,7 @@ struct opal_read_write_table {
 #define OPAL_FL_LOCKED			0x00000008
 #define OPAL_FL_MBR_ENABLED		0x00000010
 #define OPAL_FL_MBR_DONE		0x00000020
+#define OPAL_FL_SUM_SUPPORTED		0x00000040
 
 struct opal_status {
 	__u32 flags;