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Re: [Qemu-devel] [PATCH v3 3/6] block QMP: Drop query-block member "type
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH v3 3/6] block QMP: Drop query-block member "type" (type= in info block) |
Date: |
Thu, 12 May 2011 19:54:40 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) |
Luiz Capitulino <address@hidden> writes:
> On Thu, 12 May 2011 19:12:56 +0200
> Markus Armbruster <address@hidden> wrote:
>
>> Luiz Capitulino <address@hidden> writes:
>>
>> > On Thu, 12 May 2011 17:05:12 +0200
>> > Markus Armbruster <address@hidden> wrote:
>> >
>> >> Its value is unreliable: a block device used as floppy has type
>> >> "floppy" if created with if=floppy, but type "hd" if created with
>> >> if=none.
>> >>
>> >> That's because with if=none, the type is at best a declaration of
>> >> intent: the drive can be connected to any guest device. Its type is
>> >> really the guest device's business. Reporting it here is wrong.
>> >
>> > It reports how the guest is using the device, right? I'd say that's what
>> > users/clients are interested in knowing.
>>
>> The value is *unreliable*. It may or may not match how the guest is
>> using the device. I doubt users are interested in unreliable
>> information.
>
> Can't it be fixed? And how are users/clients supposed to find out how
> the guest is using its block devices?
To find out more about the guest's devices, examine the guest's devices:
info qtree.
You don't expect to find the guest serial devices in in "info chardev",
either. query-block's type member is a mistake, because it mixes up
guest device info with the host device info. Dropping it is a bug fix.
The fact that its value is unreliable is merely icing on the cake.
>> > Also, we can't just drop it from QMP. We should first note it's deprecated.
>>
>> Would you accept a change to the more honest value "unknown" for the
>> deprecation period?
>
> We have to avoid breaking the protocol. Changing something that has always
> been reported as 'cdrom' to 'unknown' will likely cause as many as damages
> as dropping the command.
I can cause damage only if somebody is using it. Which I doubt.
Remember, the value is unreliable. It's a *lie*. We can stop lying in
two ways: shut up (drop member "type"), or tell the truth (change the
value to "unknown", which is a documented value of "type").
> The best solution I can think of is noting in the documentation that the
> information is unreliable and explain what clients interested in knowing
> this info should do.
I'd be much more willing to jump through compatibility hoops if there
was *one* known user of this particular detail of QMP.
But if you insist on us continuing to lie, I'll find a way to continue
to lie. I'm resisting it, because I think it's a disservice to our
users.
- Re: [Qemu-devel] [PATCH v2 0/5] Split ide-drive and scsi-disk qdevs, and more, (continued)
- Re: [Qemu-devel] [PATCH v2 0/5] Split ide-drive and scsi-disk qdevs, and more, Kevin Wolf, 2011/05/10
- [Qemu-devel] [PATCH v2 0/5] Split ide-drive and scsi-disk qdevs, and more, Markus Armbruster, 2011/05/12
- [Qemu-devel] [PATCH v3 4/6] blockdev: Store -drive option media in DriveInfo, Markus Armbruster, 2011/05/12
- [Qemu-devel] [PATCH v3 5/6] block: Remove type hint, it's guest matter, doesn't belong here, Markus Armbruster, 2011/05/12
- [Qemu-devel] [PATCH v3 6/6] defaults: ide-cd and scsi-cd devices suppress default CD-ROM, Markus Armbruster, 2011/05/12
- [Qemu-devel] [PATCH v3 3/6] block QMP: Drop query-block member "type" (type= in info block), Markus Armbruster, 2011/05/12
- Re: [Qemu-devel] [PATCH v3 3/6] block QMP: Drop query-block member "type" (type= in info block), Luiz Capitulino, 2011/05/12
- Re: [Qemu-devel] [PATCH v3 3/6] block QMP: Drop query-block member "type" (type= in info block), Markus Armbruster, 2011/05/12
- Re: [Qemu-devel] [PATCH v3 3/6] block QMP: Drop query-block member "type" (type= in info block), Luiz Capitulino, 2011/05/12
- Re: [Qemu-devel] [PATCH v3 3/6] block QMP: Drop query-block member "type" (type= in info block),
Markus Armbruster <=
- Re: [Qemu-devel] [PATCH v3 3/6] block QMP: Drop query-block member "type" (type= in info block), Luiz Capitulino, 2011/05/12
- Re: [Qemu-devel] [PATCH v3 3/6] block QMP: Drop query-block member "type" (type= in info block), Markus Armbruster, 2011/05/13
- Re: [Qemu-devel] [PATCH v3 3/6] block QMP: Drop query-block member "type" (type= in info block), Luiz Capitulino, 2011/05/13
- Re: [Qemu-devel] [PATCH v3 3/6] block QMP: Drop query-block member "type" (type= in info block), Markus Armbruster, 2011/05/13
- Re: [Qemu-devel] [PATCH v3 3/6] block QMP: Drop query-block member "type" (type= in info block), Luiz Capitulino, 2011/05/13
[Qemu-devel] [PATCH v3 1/6] ide: Split qdev "ide-drive" into "ide-hd" and "ide-cd", Markus Armbruster, 2011/05/12
[Qemu-devel] [PATCH v3 2/6] scsi: Split qdev "scsi-disk" into "scsi-hd" and "scsi-cd", Markus Armbruster, 2011/05/12
Re: [Qemu-devel] [PATCH v2 0/5] Split ide-drive and scsi-disk qdevs, and more, Markus Armbruster, 2011/05/12