On Mar 26, 2012, at 2:17 AM, Cong Meng wrote:
> I drafted some description. Should I make an HTML version?
Yes, matching the style of the other ones, once the issues that are raised are
resolved.
(Of course, for the diagrams, we just cheat and use <pre>.)
> LINKTYPE_VIRTIO_SCSI
>
> Packet structure
>
> +---------------+
> | Pack Type |
> | (4 Octets) |
> +---------------+
> | Tag |
> | (4 Octets) |
> +---------------+
> | Initiator |
> | (4 Octets) |
> +---------------+
> | Target |
> | (4 Octets) |
> +---------------+
> | Lun |
> | (4 Octets) |
> +---------------+
> | CDB Size |
> | (4 Octets) |
> +---------------+
> | Sense Size |
> | (4 Octets) |
> +---------------+
> | Header Size |
> | (4 Octets) |
> +---------------+
> | Data Size |
> | (4 Octets) |
> +---------------+
> | |
> | Header |
> | |
> +---------------+
> | |
> | Data |
> | |
> +---------------+
>
>
> Description
>
> Pack Type:
> REQ_CMD 0x000
> REQ_TMF 0x010
> REQ_ANQ 0x011
> REQ_ANS 0x012
>
> RESP_CMD 0x100
> RESP_TMF 0x110
> RESP_ANQ 0x111
> RESP_ANS 0x112
So what do the packet types mean? Are they:
REQ_CMD SCSI command
RESP_CMD SCSI command response
REQ_TMF task management function
RESP_TMF task management function response
REQ_ANQ asynchronous notification query
RESP_ANQ asynchronous notification query response
REQ_ANS asynchronous notification subscription
RESP_ANS asynchronous notification subscription response?
And do they all have the same contents, with the same fields filled in, or are
some fields not used for some packet types?
> Tag:
> The tag to match a response to corresponding request.
I.e., both requests and responses have tag values, and the tag values for a
given request and its response are the same?
> CDB Size:
> The maximal size of CDB.
>
> Sense Size:
> The maximal size of Sense data.
So is that the maximum size or the actual size? The description of a SCSI
command request is
struct virtio_scsi_req_cmd {
// Read−only
u8 lun[8];
u64 id;
u8 task_attr ;
u8 prio;
u8 crn;
char cdb [ cdb_size ] ;
char dataout [ ] ;
// Write−only part
u32 sense_len ;
u32 residual ;
u16 status_qualifier ;
u8 status ;
u8 response ;
u8 sense [ sense_size ];
char datain [ ] ;
};
so would "CDB Size" be the same as cdb_size and "Sense Size" be the same as
sense_size?
> Header Size:
> The size of the header of a request/response.
>
> Data Size:
> The size of Data-Out or Data-In.
>
> Header:
> The request or response header.
> This header is described in Appendix H of the virtio specification:
> http://ozlabs.org/~rusty/virtio-spec/virtio-0.9.4.pdf
Are the headers:
REQ_CMD, RESP_CMD struct virtio_scsi_req_cmd
REQ_TMF, RESP_TMF struct virtio_scsi_ctrl containing
struct virtio_scsi_ctrl_tmf
REQ_ANQ, RESP_ANQ struct virtio_scsi_ctrl containing
struct virtio_scsi_ctrl_an
REQ_ANS, RESP_ANS struct virtio_scsi_ctrl containing
struct virtio_scsi_ctrl_an
Or is the header for a REQ_xxx the "Read-only part" and for a RESP_XXX the
"Write-only part"?
And do the headers include the LUN, given that the packet structure also
includes a LUN - although the packet structure's LUN is 4 bytes rather than 8
bytes?
Do they include the type field in struct virtio_scsi_ctrl, given that the type
field seems to be VIRTIO_SCSI_T_TMF for REQ_TMF/RESP_TMF,
VIRTIO_SCSI_T_AN_QUERY for REQ_ANQ/RESP_ANQ, and VIRTIO_SCSI_T_AN_SUBSCRIBE for
REQ_ANS/RESP_ANS, so it's redundant?
> Data:
> Data-Out or Data-In block.
The request description above includes "dataout" and "datain" fields; are those
absent from the Header field and, instead, contained in the Data field?
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