basic domain validation patches- 3rd and final call
scottl at samsco.org
Wed Nov 15 04:45:46 UTC 2006
Go for it!
Matthew Jacob wrote:
> Please review, or these will be going in as the basis for ongoing
> work. They aren't perfect, but I believe that they are a sorely needed
> start. Speak now or forever hold your piece.
> On 11/2/06, mjacob at freebsd.org <mjacob at freebsd.org> wrote:
>> See http://people.freebsd.org/~mjacob/DV_PATCHES
>> The ANSI document on Domain Validation gives an algorithm for doing
>> Basic Domain Validation as, in part:
>> Send an INQUIRY command to a SCSI device 3 times- twice with the
>> default transfer agreement and once with the transfer agreement set
>> to the fastest supported values. The Basic test fails when the first
>> 36 bytes of data returned at the negotiated synchronous speed does not
>> match the data received at the asynchronous transfer speed. In
>> addition, the Basic test fails if a CRC error (or parity error for
>> non-DT clocking) or a timeout occurs. If data miscompare occurs, the
>> test should be repeated (e.g., this could be due to the target changing
>> INQUIRY data during SCSI device initialization). After a finite number
>> of retries, if data miscompare recurs then fall-back should be
>> attempted (see 5.5.2).
>> and 5.5.2 has:
>> If Basic or Enhanced tests fail, a fall-back setting is set and the
>> tests are performed again. The recommended fall-back order is:
>> 1. fast-160
>> 2. fast-80
>> 3. fast-40 (with DT clocking enabled)
>> 4. fast-40 (with ST clocking enabled)
>> 5. fast-20
>> 6. fast-10; and
>> 7. asynchrnous transfer.
>> I've done an implementation interwoven into the probe code in cam_xpt
>> such that the following occurs..
>> The normal sequence is:
>> INQUIRY (short)
>> INQUIRY (long)
>> ('default' sync settings are enabled)
>> I've changed <END> to be:
>> The idea here is to leverage the two initial INQUIRY commands done at
>> async mode and compare with the last known one and to do *two*
>> additional INQUIRY commands (at speed) to see if they compare with the
>> last ASYNC long INQUIRY command. If they don't, we can do backoff and
>> just re-enter the state machine at PROBE_TUR_FOR_NEGOTIATION.
>> The backoff doesn't do DT/ST settings, but just simply increments the
>> sync_period factor until we hit 0xf (5 MHz) and then drops to async.
>> I don't mess with PPR settings on the theory that the SIM will do the
>> right thing with PPR settings depending on the values of sync period and
>> By doing fault injection (e..g, failed compares) I've done some testing
>> and this *appears* to do what one would want.
>> Any comments? I *know* there are people out there on this list who have
>> more experience with DV than I do so I'd appreciate some comments.
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