Re: [Qemu-devel] [RfC PATCH 0/5] console: qom-ify & extent screendump monitor command

[Eric Blake]

On 04/18/2013 03:01 AM, Gerd Hoffmann wrote:
>   Hi,
> 
> This patch qom-ifies the QemuConsoles and adds an new, optional
> parameter to the screendump command to specify the device you
> want dump from.
> 
> Question for the QOM guys: where in the tree should the QemuConsoles
> show up?  I can't find anything in the tree doing this.  I've placed
> them below /backend.  See patch #2.  Ok?  Better suggestions?
> 
> Question for the libvirt guys:  Is it ok for libvirt to just extend the
> existing screendump command?  Can libvirt figure there is a new
> (optional) parameter?  See patch #5.

The existing libvirt API is:

char *
virDomainScreenshot(virDomainPtr domain,
                    virStreamPtr stream,
                    unsigned int screen,
                    unsigned int flags)

which uses the screen argument to distinguish both between devices and
heads on a given device:

 * The screen ID is the sequential number of screen. In case of multiple
 * graphics cards, heads are enumerated before devices, e.g. having
 * two graphics cards, both with four heads, screen ID 5 addresses
 * the second head on the second card.

So yes, I think libvirt will be able to drive the new command by knowing
how many heads appear per device, then passing in the appropriate named
device to the QMP command.  And yes, I'll review patch 5 regarding
interface design.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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