Re: [PATCH RFC 0/6] libata/scsi/libsas: Allocate SCSI device earlier for ata port probe

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

On 9/21/22 17:24, John Garry wrote:
> On 21/09/2022 05:04, Damien Le Moal wrote:
>> On 9/20/22 19:27, John Garry wrote:
>>> Currently for libata the SCSI device (sdev) associated with an 
>>> ata_device
>>> is allocated when the port probe has completed.
>>>
>>> It's useful to have the SCSI device and its associated request queue
>>> available earlier for the port probe. Specifically if we have the
>>> request queue available, then we can:
>>> - Easily put ATA qc in SCSI cmnd priv data
>>> - Send ATA internal commands on SCSI device request queue for [0]. The
>>>    current solution there is to use the shost sdev request queue, which
>>>    isn't great.
>>> This series changes the ata port probe to alloc the sdev in the
>>> ata_device revalidation, and then just do a SCSI starget scan 
>>> afterwards.
>>>
>>> Why an RFC?
>>> 1. IPR  driver needs to be fixed up - it does not use ATA EH port probe
>>>     Mail [1] needs following up
>>
>> Yes. If IPR could be converted to ata error_handler, a lot of code can 
>> be simplified in libata too.
> 
> Hmmm... yeah, it would be good to see progress there.
> 
>>
>>> 2. SATA PMP support needs verification, but I don't have a setup
>>
>> Port multiplier behind a sas HBA will be challenging to setup :)
>> I can try, but I will need to open up one of my servers and hook a 
>> small PMP box to one of the pm8001 plugs. I may have the cables for 
>> that... Let me check.
> 
> I was more thinking of just AHCI with a port multiplier.

OK. I got confused :)
Easy then, my test box is all hooked up already.
Will give this a spin.

> 
> As for SAS controllers, I don't think it's something to be concerned 
> about. For a start, I know for sure that hisi_sas HW does not support 
> port multipliers, and I don't think that pm8001 does either. In 
> addition, libsas does not even support it - I did see a series in the 
> scsi list from years ago (to support it), but it did not progress.
> 
> Thanks,
> John

-- 
Damien Le Moal
Western Digital Research