Re: [PATCH v3 3/3] Add ata pass-through path for ZAC commands.

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On Fri, Jun 10, 2016 at 2:19 AM, Hannes Reinecke <hare@xxxxxxx> wrote:
> On 06/10/2016 09:10 AM, Shaun Tancheff wrote:
>> The current generation of HBA SAS adapters support connecting SATA
>> drives and perform SCSI<->ATA translations in hardware.
>> Unfortunately the ZBC commands are not being translate (yet).
>>
>> Currently users of SAS controllers can only send ZAC commands via
>> ata pass-through.
>>
>> This method overloads the meaning of REQ_META to direct ZBC commands
>> to construct ZAC equivalent ATA pass through commands.
>> Note also that this approach expects the initiator to deal with the
>> little endian result due to bypassing the normal translation layers.
>>
>> Signed-off-by: Shaun Tancheff <shaun.tancheff@xxxxxxxxxxx>
>> ---
>> So this patch isn't the right way to work around hardware that is
>> missing features (mixing ATA commands in SCSI interface code) it
>> maybe useful for end users in the near term who have HBA SAS
>> controllers that don't support ZBC <-> ZAC translations.
>>
> And indeed, this patch isn't right.
> It is just for a very specific SAS HBA (mpt2sas/mpt3sas).
> Other SAS HBAs like isci and hisi_sas work just nicely here.

That is good to know there are some vendors that are on the ball.

> So a translation into a ATA_16 command is _wrong_.
> If you need to do this you'll have to move it into the LLDD itself.
> Or use blacklisting to invoke this behaviour.
> But _not_ in the general code path.

Agreed. Thanks!

> Cheers,
>
> Hannes
> --
> Dr. Hannes Reinecke                Teamlead Storage & Networking
> hare@xxxxxxx                                   +49 911 74053 688
> SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
> GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
> HRB 21284 (AG Nürnberg)

-- 
Shaun Tancheff
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