scsi: esp_scsi: Stop using the SCSI pointer

Set .cmd_size in the SCSI host template instead of using the SCSI pointer
from struct scsi_cmnd. This patch prepares for removal of the SCSI pointer
from struct scsi_cmnd.

Link: https://lore.kernel.org/r/20220218195117.25689-20-bvanassche@acm.orgReviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/esp_scsi.c

@@ -2678,6 +2678,7 @@ struct scsi_host_template scsi_esp_template = {
 	.sg_tablesize		= SG_ALL,
 	.max_sectors		= 0xffff,
 	.skip_settle_delay	= 1,
+	.cmd_size		= sizeof(struct esp_cmd_priv),
 };
 EXPORT_SYMBOL(scsi_esp_template);
 
@@ -2739,9 +2740,6 @@ static struct spi_function_template esp_transport_ops = {
 
 static int __init esp_init(void)
 {
-	BUILD_BUG_ON(sizeof(struct scsi_pointer) <
-		     sizeof(struct esp_cmd_priv));
-
 	esp_transport_template = spi_attach_transport(&esp_transport_ops);
 	if (!esp_transport_template)
 		return -ENODEV;

drivers/scsi/esp_scsi.h

@@ -262,7 +262,8 @@ struct esp_cmd_priv {
 	struct scatterlist	*cur_sg;
 	int			tot_residue;
 };
-#define ESP_CMD_PRIV(CMD)	((struct esp_cmd_priv *)(&(CMD)->SCp))
+
+#define ESP_CMD_PRIV(cmd)	((struct esp_cmd_priv *)scsi_cmd_priv(cmd))
 
 /* NOTE: this enum is ordered based on chip features! */
 enum esp_rev {