SAS SMP PHY CONTROL function: PPTV and programmed link rate fields

Gerry.Houlder at seagate.com Gerry.Houlder at seagate.com
Wed Jan 22 13:53:27 PST 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* Gerry.Houlder at seagate.com
*

Even with option 2, you will still have to define a response for the case
of a host sending a value in a changeable field that is not supported by
the target end. This problem is still present no matter which of the first
3 options is chosen. I agree that a CHECK CONDITION is not what we want. I
see the PHY CONTROL followed by DISCOVER behavior more like the PPR message
negotiation sequence, where the first message says what you want and the
second says what the other end can honor (and then becomes the final
agreement). I would also assume that if one of the parameters is negotiated
to a new value, the new value doesn't take effect until after the CLOSE of
the current connection.



                                                                                                
                    George                                                                      
                    Penokie              To:     Gerry.Houlder at seagate.com                      
                    <gop at us.ibm.c        cc:     t10 <t10 at t10.org>                              
                    om>                  Subject:     Re: SAS SMP PHY CONTROL function: PPTV    
                    No Phone Info        and programmed link rate fields                        
                    Available                                                                   
                                                                                                
                    01/22/2003                                                                  
                    01:56 PM                                                                    
                                                                                                
                                                                                                








Gerry,
Your comments about using option three would work but I see some problems.
One is that the rules for rounding require you to generate a check
condition. Text from SPC-3

When parameter rounding is implemented, a device server that receives a
parameter value that is not an exact
supported value shall adjust the value to one that it supports and shall
return CHECK CONDITION status with a
sense key of RECOVERED ERROR. The additional sense code shall be set to
ROUNDED PARAMETER. The
application client should issue an appropriate command to learn what value
the device server has selected.

The other problem is that I don't like the idea of a device ignoring
parameters. That can lead to problems in that the initiator thinks the
values are set one way when in reality they are not.

Given that I would prefer option 2 which states a 0 value in a field means
no change to the value.

Bye for now,
George Penokie

Dept 2C6  114-2 N212
E-Mail:    gop at us.ibm.com
Internal:  553-5208
External: 507-253-5208   FAX: 507-253-2880





                      Gerry.Houlder at sea
                      gate.com                 To:       t10 at t10.org
                      Sent by:                 cc:
                      owner-t10 at t10.org        Subject:  Re: SAS SMP PHY
CONTROL function: PPTV and programmed link rate fields


                      01/22/2003 09:24
                      AM






* From the T10 Reflector (t10 at t10.org), posted by:
* Gerry.Houlder at seagate.com
*
I prefer option 3.

However I don't think the DISCOVER function needs to set the bits if the
fields are writeable. If the fields are not writable the "target" end will
just ignore whatever is sent in those fields and use the predetermined
value. If they are writeable the target should round the value sent to the
nearest supported value if the exact value is not supported. This kind of
rounding rule is already described in SCSI. The initiator can discover
whether rounding is occurring (or if the value is even changeable) by doing
DISCOVER after the PHY CONTROL operation.

>3. Add "set xyz field" bits
>
>Add "Set PPTV" and "Set Programmed Link Rates" bits in byte 11.
>Regardless of Phy Operation, honor the associated fields if the
>corresponding Set bit is one; ignore them if the Set bit is zero.
>
>The DISCOVER function would return these bits in byte 11 set to 1 if the
>target supports those as writable fields.



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