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To:     Hannes Reinecke <hare@suse.de>
Cc:     Bart Van Assche <bvanassche@acm.org>,
        Lee Duncan <leeman.duncan@gmail.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
        Lee Duncan <lduncan@suse.com>, Martin Wilck <mwilck@suse.com>
Subject: Re: [PATCH] scsi: core: Add BLIST_NO_ASK_VPD_SIZE for some VDASD
From:   "Martin K. Petersen" <martin.petersen@oracle.com>
Organization: Oracle Corporation
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        <11a582f0-723c-95e1-0e44-0a19e1a8a9a8@acm.org>
        <4a1da181-8a54-d2f8-6d19-d9c1982ab044@suse.de>
Date:   Mon, 07 Nov 2022 21:50:23 -0500
In-Reply-To: <4a1da181-8a54-d2f8-6d19-d9c1982ab044@suse.de> (Hannes Reinecke's
        message of "Tue, 4 Oct 2022 08:00:56 +0200")
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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