scsi: megaraid_sas: Avoid a couple -Wflex-array-member-not-at-end warnings

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

Use the new TRAILING_OVERLAP() helper to fix the following warnings:

drivers/scsi/megaraid/megaraid_sas_fusion.h:1153:31: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/scsi/megaraid/megaraid_sas_fusion.h:1198:32: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

This helper creates a union between a flexible-array member (FAM) and a
set of MEMBERS that would otherwise follow it --in this case 'struct
MR_LD_SPAN_MAP ldSpanMap[MAX_LOGICAL_DRIVES_DYN]' and 'struct
MR_LD_SPAN_MAP ldSpanMap[MAX_LOGICAL_DRIVES]' in the corresponding
structures.

This overlays the trailing members onto the FAM (struct MR_LD_SPAN_MAP
ldSpanMap[];) while keeping the FAM and the start of MEMBERS aligned.

The static_assert() ensures this alignment remains, and it's
intentionally placed inmediately after the corresponding structures --no
blank line in between.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://patch.msgid.link/aM1E7Xa8qYdZ598N@kspp
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.h b/drivers/scsi/megaraid/megaraid_sas_fusion.h
index b677d80e587472fde9047e1f0d73e2b3d9c1b8f1..ddeea0ee283442bc75ea1425872436e3c418b68f 100644 (file)
--- a/drivers/scsi/megaraid/megaraid_sas_fusion.h
+++ b/drivers/scsi/megaraid/megaraid_sas_fusion.h
@@ -1150,9 +1150,13 @@ typedef struct LOG_BLOCK_SPAN_INFO {
 } LD_SPAN_INFO, *PLD_SPAN_INFO;
 
 struct MR_FW_RAID_MAP_ALL {
-       struct MR_FW_RAID_MAP raidMap;
-       struct MR_LD_SPAN_MAP ldSpanMap[MAX_LOGICAL_DRIVES];
+       /* Must be last --ends in a flexible-array member. */
+       TRAILING_OVERLAP(struct MR_FW_RAID_MAP, raidMap, ldSpanMap,
+               struct MR_LD_SPAN_MAP ldSpanMap[MAX_LOGICAL_DRIVES];
+       );
 } __attribute__ ((packed));
+static_assert(offsetof(struct MR_FW_RAID_MAP_ALL, raidMap.ldSpanMap) ==
+             offsetof(struct MR_FW_RAID_MAP_ALL, ldSpanMap));
 
 struct MR_DRV_RAID_MAP {
        /* total size of this structure, including this field.
@@ -1194,10 +1198,13 @@ struct MR_DRV_RAID_MAP {
  * And it is mainly for code re-use purpose.
  */
 struct MR_DRV_RAID_MAP_ALL {
-
-       struct MR_DRV_RAID_MAP raidMap;
-       struct MR_LD_SPAN_MAP ldSpanMap[MAX_LOGICAL_DRIVES_DYN];
+       /* Must be last --ends in a flexible-array member. */
+       TRAILING_OVERLAP(struct MR_DRV_RAID_MAP, raidMap, ldSpanMap,
+               struct MR_LD_SPAN_MAP ldSpanMap[MAX_LOGICAL_DRIVES_DYN];
+       );
 } __packed;
+static_assert(offsetof(struct MR_DRV_RAID_MAP_ALL, raidMap.ldSpanMap) ==
+             offsetof(struct MR_DRV_RAID_MAP_ALL, ldSpanMap));