SAS SSP sense data that is not a multiple of 4

Elliott, Robert (Server Storage) Elliott at hp.com
Sun Feb 2 11:05:53 PST 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
*
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A Quantum comment questions how non-multiple of 4 amounts of sense data
should be handled.=20

a) SENSE DATA LIST LENGTH shall be a multiple of 4.  If the sense data
is not, pad bytes are included at the end of the sense data so the =
SENSE
DATA field matches the indicated SENSE DATA LIST LENGTH.  This is the
current SAS specification.

b) SENSE DATA LIST LENGTH may be any value.  If the sense data is not a
multiple of 4, the header NUMBER OF FILL BYTES field indicates how many
fill bytes are included at the end of the frame.  (the SENSE DATA field
is the last field in the frame, so there is no confusion about the =
start
of the next field)

None of the other transport protocols mention that SENSE DATA LIST
LENGTH needs to be a multiple of 4, so I suspect they take approach b).
I think we should probably switch to approach b).


Comment:=20
49. (T) Section 9.2.2.5.4, forth paragraph. Add statement that the
NUMBER OF FILL BYTES field in the frame header shall indicate the =
number
of fill bytes added.

Current SAS wording:=20
the sense data list length field shall be set to a non-zero value
indicating the number of bytes in the sense data field. The sense data
list length field shall not be larger than 1 000 (see table 95) and
shall be a multiple of four. If the sense data field size is not a
multiple of four, it shall be padded to make its size a multiple of
four. The value of the pad bytes are vendor specific

FCP-2:=20
If the FCP_SNS_LEN_VALID bit is one, the FCP_SNS_LEN field specifies =
the
number of valid bytes of FCP_SNS_INFO.=20
If the FCP_SNS_LEN_VALID bit is zero, the FCP_SNS_LEN field is not =
valid
and shall be treated as if its value were=20
zero. No FCP_SNS_INFO is provided.=20
The FCP_SNS_LEN field is always included in the FCP_RSP IU.=20

SRP:=20
If sense data is provided, SNSVALID shall be set to one and the SENSE
DATA LIST LENGTH field shall specify the=20
number of bytes in the SENSE DATA field.=20

iSCSI:=20
10.4.7.1 SenseLength=20
Length of Sense Data.=20


--=20
Rob Elliott, elliott at hp.com=20
Hewlett-Packard Industry Standard Server Storage Advanced Technology=20
 <https://ecardfile.com/id/RobElliott>
https://ecardfile.com/id/RobElliott=20




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SAS SSP sense data that is not a multiple of 4 A Quantum comment questions how = non-multiple of 4 amounts of sense data should be handled. a) SENSE DATA LIST LENGTH shall be a = multiple of 4.  If the sense data is not, pad bytes are included = at the end of the sense data so the SENSE DATA field matches the = indicated SENSE DATA LIST LENGTH.  This is the current SAS = specification. b) SENSE DATA LIST LENGTH may be any = value.  If the sense data is not a multiple of 4, the header = NUMBER OF FILL BYTES field indicates how many fill bytes are included = at the end of the frame.  (the SENSE DATA field is the last field = in the frame, so there is no confusion about the start of the next = field) None of the other transport protocols = mention that SENSE DATA LIST LENGTH needs to be a multiple of 4, so I = suspect they take approach b).  I think we should probably switch = to approach b). 
Comment: 
49. (T) Section 9.2.2.5.4, forth = paragraph. Add statement that the NUMBER OF FILL BYTES field in the = frame header shall indicate the number of fill bytes added. Current SAS wording: 
the sense data list length field = shall be set to a non-zero value indicating the number of bytes in the = sense data field. The sense data list length field shall not be larger = than 1 000 (see table 95) and shall be a multiple of four. If the sense = data field size is not a multiple of four, it shall be padded to make = its size a multiple of four. The value of the pad bytes are vendor = specific FCP-2: 
If the FCP_SNS_LEN_VALID bit is one, = the FCP_SNS_LEN field specifies = the number of valid bytes of FCP_SNS_INFO. 
If the FCP_SNS_LEN_VALID bit is zero, = the FCP_SNS_LEN field is not = valid and shall be treated as if its value were 
zero. No FCP_SNS_INFO is provided. 
The FCP_SNS_LEN field is always included in the FCP_RSP = IU. SRP: 
If sense data is provided, = SNSVALID shall be set to one and the SENSE DATA LIST LENGTH field shall specify the 
number of bytes in the SENSE DATA field. iSCSI: 
10.4.7.1 SenseLength 
Length of Sense Data. 
-- 
Rob Elliott, elliott at hp.com 
Hewlett-Packard Industry Standard = Server Storage Advanced Technology 
https://ecardfile.com/id/RobElliott 


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