scsi: qla2xxx: Improve readability of the code that handles qla_flt_header

Declare qla_hw_data.flt as a qla_flt_header pointer instead of as a void
pointer. Add a zero-length array at the end of struct qla_flt_header to
make it clear that qla_flt_header and qla_flt_region are contiguous. This
patch removes several casts but does not change any functionality.

Cc: Himanshu Madhani <hmadhani@marvell.com>
Cc: Quinn Tran <qutran@marvell.com>
Cc: Martin Wilck <mwilck@suse.com>
Cc: Daniel Wagner <dwagner@suse.de>
Cc: Roman Bolshakov <r.bolshakov@yadro.com>
Link: https://lore.kernel.org/r/20191219004706.39039-1-bvanassche@acm.orgReviewed-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/qla2xxx/qla_def.h

@@ -3968,7 +3968,7 @@ struct qla_hw_data {
 	void		*sfp_data;
 	dma_addr_t	sfp_data_dma;
 
-	void		*flt;
+	struct qla_flt_header *flt;
 	dma_addr_t	flt_dma;
 
 #define XGMAC_DATA_SIZE	4096

drivers/scsi/qla2xxx/qla_fw.h

@@ -1471,13 +1471,6 @@ struct qla_flt_location {
 	uint16_t checksum;
 };
 
-struct qla_flt_header {
-	uint16_t version;
-	uint16_t length;
-	uint16_t checksum;
-	uint16_t unused;
-};
-
 #define FLT_REG_FW		0x01
 #define FLT_REG_BOOT_CODE	0x07
 #define FLT_REG_VPD_0		0x14
@@ -1538,6 +1531,14 @@ struct qla_flt_region {
 	uint32_t end;
 };
 
+struct qla_flt_header {
+	uint16_t version;
+	uint16_t length;
+	uint16_t checksum;
+	uint16_t unused;
+	struct qla_flt_region region[0];
+};
+
 #define FLT_REGION_SIZE		16
 #define FLT_MAX_REGIONS		0xFF
 #define FLT_REGIONS_SIZE	(FLT_REGION_SIZE * FLT_MAX_REGIONS)

drivers/scsi/qla2xxx/qla_os.c

@@ -7242,6 +7242,8 @@ qla2x00_module_init(void)
 	BUILD_BUG_ON(sizeof(struct sns_cmd_pkt) != 2064);
 	BUILD_BUG_ON(sizeof(struct verify_chip_entry_84xx) != 64);
 	BUILD_BUG_ON(sizeof(struct vf_evfp_entry_24xx) != 56);
+	BUILD_BUG_ON(sizeof(struct qla_flt_region) != 16);
+	BUILD_BUG_ON(sizeof(struct qla_flt_header) != 8);
 
 	/* Allocate cache for SRBs. */
 	srb_cachep = kmem_cache_create("qla2xxx_srbs", sizeof(srb_t), 0,

drivers/scsi/qla2xxx/qla_sup.c

@@ -669,8 +669,8 @@ qla2xxx_get_flt_info(scsi_qla_host_t *vha, uint32_t flt_addr)
 
 	struct qla_hw_data *ha = vha->hw;
 	uint32_t def = IS_QLA81XX(ha) ? 2 : IS_QLA25XX(ha) ? 1 : 0;
-	struct qla_flt_header *flt = (void *)ha->flt;
-	struct qla_flt_region *region = (void *)&flt[1];
+	struct qla_flt_header *flt = ha->flt;
+	struct qla_flt_region *region = &flt->region[0];
 	uint16_t *wptr, cnt, chksum;
 	uint32_t start;
 
@@ -2652,18 +2652,15 @@ qla28xx_get_flash_region(struct scsi_qla_host *vha, uint32_t start,
     struct qla_flt_region *region)
 {
 	struct qla_hw_data *ha = vha->hw;
-	struct qla_flt_header *flt;
-	struct qla_flt_region *flt_reg;
+	struct qla_flt_header *flt = ha->flt;
+	struct qla_flt_region *flt_reg = &flt->region[0];
 	uint16_t cnt;
 	int rval = QLA_FUNCTION_FAILED;
 
 	if (!ha->flt)
 		return QLA_FUNCTION_FAILED;
 
-	flt = (struct qla_flt_header *)ha->flt;
-	flt_reg = (struct qla_flt_region *)&flt[1];
 	cnt = le16_to_cpu(flt->length) / sizeof(struct qla_flt_region);
-
 	for (; cnt; cnt--, flt_reg++) {
 		if (flt_reg->start == start) {
 			memcpy((uint8_t *)region, flt_reg,