Re: [Qemu-devel] [PATCH 8/9] blockdev: add x-blockdev-set-iothread testing command

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Tue, Dec 05, 2017 at 08:40:42AM -0600, Eric Blake wrote:
> On 12/05/2017 04:41 AM, Stefan Hajnoczi wrote:
> > +##
> > +# @x-blockdev-set-iothread:
> > +#
> > +# Move @node and its children into the @iothread.  If @iothread is empty then
> > +# move @node and its children into the main loop.
> > +#
> > +# The node must not be attached to a BlockBackend.
> > +#
> > +# @node-name: the name of the block driver node
> > +#
> > +# @iothread: the name of the IOThread object
> > +#
> 
> > +# 2. Move a node into the main loop
> > +# -> { "execute": "x-blockdev-set-iothread",
> > +#      "arguments": { "node-name": "disk1",
> > +#                     "iothread": "" } }
> 
> Eww. Special casing of the empty string.  Would it be better design to
> have iothread be optional, and to omit it to move a node into the main
> loop?  Or use the StrOrNull type to allow JSON null instead of "" to
> mean the main loop?

I deliberated about this and chose the empty string because it has
special meaning in other QMP commands too.  But I agree that it's ugly.

StrOrNull is cleaner than using the empty string.  Making it optional
feels strange to me so I'll switch to StrOrNull.

Stefan

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