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From: Markus Armbruster <armbru@redhat.com>
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Date: Mon, 28 Jan 2019 17:55:14 +0100
In-Reply-To: <20190128144147.GA5756@localhost.localdomain> (Kevin Wolf's
	message of "Mon, 28 Jan 2019 15:41:47 +0100")
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Subject: Re: [Qemu-devel] [PATCH 2/3] scsi-disk: Add device_id property
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To: Kevin Wolf <kwolf@redhat.com>
Cc: Peter Krempa <pkrempa@redhat.com>, qemu-block@nongnu.org, libvir-list@redhat.com, qemu-devel@nongnu.org, pbonzini@redhat.com

Kevin Wolf <kwolf@redhat.com> writes:

> Am 28.01.2019 um 09:50 hat Peter Krempa geschrieben:
[...]
>> 2) Is actually using 'scsi-cd'/'scsi-hd' the better option than
>> 'scsi-disk'?
>
> Yes, scsi-disk is a legacy device. Maybe we should formally deprecate
> it.

There's an internal use in scsi_bus_legacy_add_drive(), which in turn
powers two legacy features:

1. -drive if=scsi

   Creates scsi-disk frontends.

   Only works with onboard HBAs since commit 14545097267, v2.12.0.

2. -device usb-storage

   Bad magic: usb-storage pretends to be a block device, but it's really
   a SCSI bus that can serve only a single device, which it creates
   automatically.

If we deprecate scsi-disk, we should deprecate these, too.  Can't say
whether that's practical right now.

>> 3) Since upstream libvirt supports qemu-1.5 and newer and 'scsi-cd' is
>> already supported there, can we assume that all newer versions support
>> it? (Basically the question is whether it can be compiled out by
>> upstream means).
>
> I think so.

Compiling out scsi-hd or scsi-cd, but not scsi-disk would be silly.  All
three devices are in scsi-disk.c.  You'd have to hack that up to be
silly.