linux-kernel - Re: [PATCH] scsi: core: Add BLIST_NO_ASK_VPD

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Message-ID: <yq1k046kwyv.fsf@ca-mkp.ca.oracle.com>
Date:   Mon, 07 Nov 2022 21:50:23 -0500
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     Hannes Reinecke <hare@...e.de>
Cc:     Bart Van Assche <bvanassche@....org>,
        Lee Duncan <leeman.duncan@...il.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lee Duncan <lduncan@...e.com>, Martin Wilck <mwilck@...e.com>
Subject: Re: [PATCH] scsi: core: Add BLIST_NO_ASK_VPD_SIZE for some VDASD

Hannes,

I have been contemplating this for a bit.

>> Has it been considered instead of introducing a blacklist flag to not
>> use the reported VPD page size if the device reports that the VPD
>> page size is zero? I am not aware of any VPD pages for which zero is
>> a valid size.

That would also be my preferred approach, I think. I haven't received
any bug reports about devices returning short VPD pages since this
change was introduced. So I think I'd prefer falling back to a
(hopefully small) default if a device returns a 0 page length.

Now, my question is which VPD pages are actually supported by this
device and how large are they?

> But pre-SPC drives will ignore the VPD bit in the inquiry size. And
> these devices do not set an additional length in the inquiry data

Can you elaborate a bit on your experience with older devices? I checked
SCSI-2 (1991) and don't see any indication this would be valid behavior
even back then.

-- 
Martin K. Petersen	Oracle Linux Engineering