Re: [Qemu-devel] [PATCH 00/18] qom: dynamic properties and composition tree

[Anthony Liguori <aliguori@us.ibm.com>]

On 11/30/2011 03:03 PM, Anthony Liguori wrote:
> This is a follow up to my previous series to get us started in the QOM
> direction.  A few things are different this time around.  Most notably:
>
>   1) Devices no longer have names.  Instead, path names are always used to
>      identify devices.
>
>   2) In order to support (1), dynamic properties are now supported.
>
>   3) The concept of a "root device" has been introduced.  The root device is
>      roughly modelling the motherboard of a machine.  This type is a container
>      type and it's best to think of it as something like a PCB board I guess.
>
> To try it out, here's an example session:
>
> Launch:
>
> anthony@titi:~/build/qemu$ x86_64-softmmu/qemu-system-x86_64 -hda ~/images/linux.img -snapshot -device virtio-balloon-pci,id=foo -qmp unix:/tmp/server.sock,server,nowait
>
> Explore the object model:
>
> anthony@titi:~/git/qemu/QMP$ ./qom-list /
> peripheral/
> i440fx/
> anthony@titi:~/git/qemu/QMP$ ./qom-list /i440fx/
> piix3/
> anthony@titi:~/git/qemu/QMP$ ./qom-list /i440fx/piix3
> rtc/
> anthony@titi:~/git/qemu/QMP$ ./qom-list /i440fx/piix3/rtc
> date
> base_year
> anthony@titi:~/git/qemu/QMP$ ./qom-get /i440fx/piix3/rtc.date
> tm_sec: 33
> tm_hour: 21
> tm_mday: 30
> tm_year: 111
> tm_mon: 10
> tm_min: 2
> anthony@titi:~/git/qemu/QMP$ ./qom-get rtc.date
> tm_sec: 38
> tm_hour: 21
> tm_mday: 30
> tm_year: 111
> tm_mon: 10
> tm_min: 2

It's probably worth adding that this is the short form.  The full path for rtc 
is /i440fx/piix4/rtc.  If user did -device virtio-pci-blk,id=rtc, then that 
device would have a full path for /peripheral/rtc.

If you did that, then just saying 'rtc.date' would through an error because the 
relative path 'rtc' is ambiguous.

The purpose of this is to give stable, unambiguous paths while still making it 
easy to use for a command line user.

Regards,

Anthony Liguori