[PATCH] megaraid_sas: Fallback to older scanning if not disks are found

[Hannes Reinecke <hare@suse.de>]

commit 21c9e160a51383d4cb0b882398534b0c95c0cc3b implemented a
new driver lookup using the MR_DCMD_LD_LIST_QUERY firmware command.
However, this command might not work properly on older firmware,
causing the command to return no drives instead of an error.
This causes a regression on older firmware as the driver will
no longer detect any drives.
This patch checks if MR_DCMD_LD_LIST_QUERY return no drives,
and falls back to the original method if so.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/megaraid/megaraid_sas_base.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/scsi/megaraid/megaraid_sas_base.c b/drivers/scsi/megaraid/megaraid_sas_base.c
index f97ec34..79dff70 100644
--- a/drivers/scsi/megaraid/megaraid_sas_base.c
+++ b/drivers/scsi/megaraid/megaraid_sas_base.c
@@ -4107,6 +4107,10 @@ megasas_ld_list_query(struct megasas_instance *instance, u8 query_type)
 		ret = megasas_issue_polled(instance, cmd);
 
 	tgtid_count = le32_to_cpu(ci->count);
+	if (tgtid_count == 0) {
+		/* No drives found, try the older LD list DCMD */
+		ret = 1;
+	}
 
 	if ((ret == 0) && (tgtid_count <= (instance->fw_supported_vd_count))) {
 		memset(instance->ld_ids, 0xff, MEGASAS_MAX_LD_IDS);
-- 
1.8.5.6