scsi: g_NCR5380: Check for chip presence before calling NCR5380_init()

Write and read back mode register to check that a chip is really there.
If no card is present, reads result in 0xff.

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Tested-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/g_NCR5380.c

@@ -248,6 +248,13 @@ static int generic_NCR5380_init_one(struct scsi_host_template *tpnt,
 		}
 	}
 
+	/* Check for vacant slot */
+	NCR5380_write(MODE_REG, 0);
+	if (NCR5380_read(MODE_REG) != 0) {
+		ret = -ENODEV;
+		goto out_unregister;
+	}
+
 	ret = NCR5380_init(instance, flags | FLAG_LATE_DMA_SETUP);
 	if (ret)
 		goto out_unregister;