In function twl_probe() at drivers/scsi/3w-sas.c:line 1564, if twl_initialize_device_extension() at line 1601 ,pci_iomap() at line 1614 and twl_reset_sequence() at line 1624 fails, function twl_probe() will return the value of variable retval, which is 0 indicating success because pci_enable_device() at line 1571 and  pci_request_regions() at line 1607 succeeded previously.But, function twl_probe() should propagate the error and return the error to its caller functions.
The related code snippets in twl_probe are as following.
twl_probe @@ drivers/scsi/3w-sas.c:line 1564

1564 static int twl_probe(struct pci_dev *pdev, const struct pci_device_id *dev_id)
1565 {	
			  ...
1571         retval = pci_enable_device(pdev);
1572         if (retval) {
1573                 TW_PRINTK(host, TW_DRIVER, 0x17, "Failed to enable pci device");
1574                 goto out_disable_device;
1575         }
			  ...			  
1601         if (twl_initialize_device_extension(tw_dev)) {
1602                 TW_PRINTK(tw_dev->host, TW_DRIVER, 0x1a, "Failed to initialize device extension");
1603                 goto out_free_device_extension;
1604         }
			  ...		
1606         /* Request IO regions */
1607         retval = pci_request_regions(pdev, "3w-sas");
1608         if (retval) {
1609                 TW_PRINTK(tw_dev->host, TW_DRIVER, 0x1b, "Failed to get mem region");
1610                 goto out_free_device_extension;
1611         }
1612 
1613         /* Save base address, use region 1 */
1614         tw_dev->base_addr = pci_iomap(pdev, 1, 0);
1615         if (!tw_dev->base_addr) {
1616                 TW_PRINTK(tw_dev->host, TW_DRIVER, 0x1c, "Failed to ioremap");
1617                 goto out_release_mem_region;
1618         }
1619 
1620         /* Disable interrupts on the card */
1621         TWL_MASK_INTERRUPTS(tw_dev);
1622 
1623         /* Initialize the card */
1624         if (twl_reset_sequence(tw_dev, 0)) {
1625                 TW_PRINTK(tw_dev->host, TW_DRIVER, 0x1d, "Controller reset failed during probe");
1626                 goto out_iounmap;
1627         }	
			  ...		
1694         return 0;
			  ...		
1700 out_iounmap:
1701         iounmap(tw_dev->base_addr);
1702 out_release_mem_region:
1703         pci_release_regions(pdev);
1704 out_free_device_extension:
1705         twl_free_device_extension(tw_dev);
1706         scsi_host_put(host);
1707 out_disable_device:
1708         pci_disable_device(pdev);
1709 
1710         return retval;
1711 } /* End twl_probe() */