Re: [Qemu-devel] [PATCH v2 4/5] console: pass Monitor to vga_hw_screen_dump/hw_vga_dump

[Alon Levy <alevy@redhat.com>]

On Wed, Mar 14, 2012 at 09:32:58AM -0300, Luiz Capitulino wrote:
> On Wed, 14 Mar 2012 08:37:13 +0000
> "Daniel P. Berrange" <berrange@redhat.com> wrote:
> 
> > > First, with this applied you will not know the size in advance.  Also
> > > one of the approaches discussed is to allow passing in a file handle.
> > > That is a possible way to handle async screendumps too: just write to
> > > the passed file handle and close it when done.  Obvious drawback is that
> > > this will not cover the classic way of specifying the output filename as
> > > argument.
> 
> As Daniel explains below, this is not a drawback and there's no problem
> supporting multiple ways of returning the image.
> 
> The real drawback of making this w/o async support is that you can't detect
> errors.
> 

You also can't detect when the writing is done (unless you continuously
try to parse the file yourself..)

> > This would not be a problem from libvirt's POV - we don't really want a
> > file on disk anyway, nor do we want to pull the whole image into memory.
> > Our ideal approach is to just have an pipe FD with QEMU, which we just
> > incrementally read image data from, and forward to the client app via
> > a libvirt stream object.
>