Some commands (such as INQUIRY) may return less data than the initiator
requested. To avoid conducting useless information, set the right residual
count to make upper layer aware of this.

Before (INQUIRY PAGE 0xB0 with 128B buffer):

$ sg_raw -r 128 /dev/sda 12 01 B0 00 80 00
SCSI Status: Good

Received 128 bytes of data:
 00 00 b0 00 3c 01 00 00 00 00 00 00 00 00 00 00 00 ...<............
 10 00 00 00 00 00 01 00 00 00 00 00 40 00 00 08 00 ...........@....
 20 80 00 00 00 00 00 00 00 00 00 20 00 00 00 00 00 .......... .....
 30 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
 40 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
 50 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
 60 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
 70 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................

After:

$ sg_raw -r 128 /dev/sda 12 01 B0 00 80 00
SCSI Status: Good

Received 64 bytes of data:
00 00 b0 00 3c 01 00 00 00 00 00 00 00 00 00 00 00 ...<............
10 00 00 00 00 00 01 00 00 00 00 00 40 00 00 08 00 ...........@....
20 80 00 00 00 00 00 00 00 00 00 20 00 00 00 00 00 .......... .....
30 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................

[mkp: clarified description]

Link: https://lore.kernel.org/r/03C41093-B62E-43A2-913E-CFC92F1C70C3@vmware.com


Signed-off-by: Matt Wang <wwentao@vmware.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>