If scsi_host_template->host_reset is NULL and the user requests an
adapter reset through
	echo adapter > /sys/class/scsi_host/hostx/host_reset
-EINVAL will be returned even though the "adapter" argument is perfectly
valid.
Change this so that we only return -EINVAL if the provided string is
invalid.  If the host does not implement a ->host_reset function we'll
return -EOPNOTSUPP.
[mkp: tweaked patch description]
Signed-off-by: weiping zhang <zhangweiping@didichuxing.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
 
        if (sht->host_reset)
                ret = sht->host_reset(shost, type);
+       else
+               ret = -EOPNOTSUPP;
 
 exit_store_host_reset:
        if (ret == 0)