[PATCH v4 13/15] scsi_debug: Implement the IO Advice Hints Grouping mode page

[Bart Van Assche <bvanassche@acm.org>]

Implement an IO Advice Hints Grouping mode page with three permanent
streams. A permanent stream is a stream for which the device server does
not allow closing or otherwise modifying the configuration of that
stream. The stream identifier enable (ST_ENBLE) bit specifies whether
the stream identifier may be used in the GROUP NUMBER field of SCSI
WRITE commands.

Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/scsi_debug.c | 42 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 40 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index a16885fcec24..98fa675cbf37 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -2552,6 +2552,36 @@ static int resp_ctrl_m_pg(unsigned char *p, int pcontrol, int target)
 	return sizeof(ctrl_m_pg);
 }
 
+enum { MAXIMUM_NUMBER_OF_STREAMS = 4 };
+
+/* IO Advice Hints Grouping mode page */
+static int resp_grouping_m_pg(unsigned char *p, int pcontrol, int target)
+{
+	/* IO Advice Hints Grouping mode page */
+	struct grouping_m_pg {
+		u8 page_code;
+		u8 subpage_code;
+		__be16 page_length;
+		u8 reserved[12];
+		struct scsi_io_group_descriptor
+			descr[MAXIMUM_NUMBER_OF_STREAMS];
+	};
+	static const struct grouping_m_pg gr_m_pg = {
+		.page_code = 0xa,
+		.subpage_code = 5,
+		.page_length = cpu_to_be16(sizeof(gr_m_pg) - 4),
+		.descr = {
+			{ .st_enble = 1 },
+			{ .st_enble = 1 },
+			{ .st_enble = 1 },
+			{ .st_enble = 0 },
+		}
+	};
+
+	BUILD_BUG_ON(sizeof(struct grouping_m_pg) != 16 + 4 * 16);
+	memcpy(p, &gr_m_pg, sizeof(gr_m_pg));
+	return sizeof(gr_m_pg);
+}
 
 static int resp_iec_m_pg(unsigned char *p, int pcontrol, int target)
 {	/* Informational Exceptions control mode page for mode_sense */
@@ -2731,9 +2761,17 @@ static int resp_mode_sense(struct scsi_cmnd *scp,
 		}
 		break;
 	case 0xa:	/* Control Mode page, all devices */
-		if (subpcode > 0x0 && subpcode < 0xff)
+		switch (subpcode) {
+		case 0:
+		case 0xff:
+			len = resp_ctrl_m_pg(ap, pcontrol, target);
+			break;
+		case 0x05:
+			len = resp_grouping_m_pg(ap, pcontrol, target);
+			break;
+		default:
 			goto bad_subpcode;
-		len = resp_ctrl_m_pg(ap, pcontrol, target);
+		}
 		offset += len;
 		break;
 	case 0x19:	/* if spc==1 then sas phy, control+discover */