Re: [Qemu-devel] [PATCH 2/2] Added target to build libvdisk

[Daniel P. Berrange]

On Mon, Aug 22, 2011 at 02:29:00PM -0500, Anthony Liguori wrote:
> On 08/22/2011 12:06 PM, Saggi Mizrahi wrote:
> >libvdisk is a library that packages qemu's handling of disk images. This
> >allows for other programs to link to it and get access to qemu image
> >file abstractions.
> >
> >To use install the lib and #include<vdisk/block.h>
> >all the bdrv_* functions work as expected.
> >
> >Signed-off-by: Saggi Mizrahi<address@hidden>
> 
> It's a good idea in principle but the approach is far too naive.
> 
> The block layer needs a good bit of modularization first.  Test
> cases need to be written, and most importantly, using the library
> shouldn't require writing a bunch of dummy functions.

There are also licensing practicalities which can cause us
some trouble/pain. For example:

> >  ######################################################################
> >+# libvdisk
> >+
> >+vdisk-obj-y = $(block-obj-y)
> >+
> >+vdisk-obj-y += qemu-tool.o qemu-error.o
> >+vdisk-obj-y += $(oslib-obj-y) $(trace-obj-y) $(block-obj-y)
> >+vdisk-obj-y += $(qobject-obj-y) $(version-obj-y) qemu-timer-common.o

$(block-obj-y) pulls in  'aio.o' which is built from aio.c which
is licensed  "GPLv2 only". So even those many files are BSD
licenses, the combined work will be GPLv2-only. Unfortunately ending
up with a libqemublock.so which is GPLv2-only is as good as useless
for libs/apps since it is incompatible with both LGPLv2(+) and GPLv3.

Now in this case aio.c is labelled as Copyright IBM / Anthony,
so IBM could likely resolve this licensing to be more widely
compatible. This could^H^Hwould become a non-trivial task if we
need to look at many files & then also any patches accepted to
those files from 3rd parties over the years :-(

Regards,
Daniel
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