Interpreting SCSI CDB response over FC(FCP-2)

Interpreting SCSI CDB response over FC(FCP-2)

[shankar krishna]

Hi,
I am looking for specific information in the SCSI response
for the CDB sent by following method.

if (ioctl(sd_fd,SCSI_IOCTL_SEND_COMMAND,&cdb_buf))
{
/* ERROR */
}

The above command sends the CDB and the response comes
as below in cdb_buf. From DGilbert's doc,(www.torque.net/sg)

   struct sdata {
    unsigned int inlen;     [i] Length of data written to device
    unsigned int outlen;    [i] Length of data read from device
    unsigned char cmd[x];   [i] SCSI command (6 <= x <= 16)
                            [o] Data read from device starts here
                            [o] On error, sense buffer starts here
    unsigned char wdata[y]; [i] Data written to device starts here
   };

Question:
1. I want to see the SCSI status byte from 12th byte of FCP_RESP
payload! how can get that?
2. Information FCP_SNS_LEN and FCP_RSP_LEN are also needed but not
able to get from the above structure as it straight away returns
the sense key structure! How to get those information?
3. If possible, can anybody throw light on how to get the Whole
FCP response payload as such??

Any other function call otherthan ioctl can fetch me this info??

Thanks,
-Shankar.





>From: Doug Ledford <dledford@redhat.com>
>To: shankar krishna <kshan01@hotmail.com>
>CC: aksumit@india.hp.com, linux-scsi@vger.kernel.org
>Subject: Re: building SCSI CDB over FC
>Date: Fri, 8 Nov 2002 18:12:44 -0500
>
>On Fri, Nov 08, 2002 at 02:03:16PM -0700, shankar krishna wrote:
> > Sumit:
> > You are correct. I sent the
> > following command to send the
> > CDB. It did send correctly.
> >
> > if (ioctl(sd_fd,SCSI_IOCTL_SEND_COMMAND,&cdb_buf))
> > {
> > /* ERROR */
> > }
> >
> > where cdb_buf is of type Scsi_Ioctl_Command.
> >
> > DGilbert:
> > "
> > Notes:
> > The SCSI command length is determined by examining the 1st byte of the
> > given command [1] . There is no way to override this.
> > "
> >
> > The above claim that 1st octet should be the length
> > of CDB is not true...In the analyser I could see
> > that "if I sent the length of CDB it is sending
> > it as OPCODE" which essentially is the first byte.
> >
> > You may want to correct it in the
> > document(www.torque.net/sg) that you
> > told me. It was very useful.
>
>I believe you are mis-interpreting the documentation.  The first byte of
>the command is the opcode, and with scsi_ioctl_send_command the code reads
>the opcode and looks it up in a table to determine the length of the scsi
>command, and that length is the length that can't be over-ridden.
>
>--
>   Doug Ledford <dledford@redhat.com>     919-754-3700 x44233
>          Red Hat, Inc.
>          1801 Varsity Dr.
>          Raleigh, NC 27606
>


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Re: Interpreting SCSI CDB response over FC(FCP-2)

[Douglas Gilbert]

shankar krishna wrote:
> Hi,
> I am looking for specific information in the SCSI response
> for the CDB sent by following method.
> 
> if (ioctl(sd_fd,SCSI_IOCTL_SEND_COMMAND,&cdb_buf))
> {
> /* ERROR */
> }
> 
> The above command sends the CDB and the response comes
> as below in cdb_buf. From DGilbert's doc,(www.torque.net/sg)
> 
>   struct sdata {
>    unsigned int inlen;     [i] Length of data written to device
>    unsigned int outlen;    [i] Length of data read from device
>    unsigned char cmd[x];   [i] SCSI command (6 <= x <= 16)
>                            [o] Data read from device starts here
>                            [o] On error, sense buffer starts here
>    unsigned char wdata[y]; [i] Data written to device starts here
>   };
> 
> Question:
> 1. I want to see the SCSI status byte from 12th byte of FCP_RESP
> payload! how can get that?

if ((res = ioctl(sd_fd,SCSI_IOCTL_SEND_COMMAND,&cdb_buf))) {
     scsi_status = res & 0xff;
     .....
}

> 2. Information FCP_SNS_LEN and FCP_RSP_LEN are also needed but not
> able to get from the above structure as it straight away returns
> the sense key structure! How to get those information?
> 3. If possible, can anybody throw light on how to get the Whole
> FCP response payload as such??
> 
> Any other function call otherthan ioctl can fetch me this info??

I'm not sure what happens in the FC world. However the scsi
subsystem mid level [which is what processes
SCSI_IOCTL_SEND_COMMAND] leaves those sort of details to the
lower level driver. The only way that I can see to get the
whole FCP response payload would be via an ioctl in the
lower level driver.

Doug Gilbert

Re: Interpreting SCSI CDB response over FC(FCP-2)

[shankar krishna]

1.
"if ((res = ioctl(sd_fd,SCSI_IOCTL_SEND_COMMAND,&cdb_buf))) {
    scsi_status = res & 0xff;
    .....
}"

Thanks. Atleast able to get Status Byte.
Question out of curiosity: if I declare
'res' as int, the return value from ioctl
was 0x28000002 which obviously give 02(Check
condition) if "&" with "ff". But I want to know
what are all the other Octets?? Any meaning
attached to them?

2.
" The only way that I can see to get the
whole FCP response payload would be via an ioctl in the
lower level driver."

Where can I consult or get doc to see there is
any way I can send probe below Mid-level driver
(or even below?)

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