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

[Anthony Liguori <anthony@codemonkey.ws>]

On 08/23/2011 11:12 AM, Daniel P. Berrange wrote:
> 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<smizrahi@redhat.com>
>>
>> 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 :-(

If there was a block driver library, I would expect it to be GPL, not LGPL.

Regards,

Anthony Liguori

>
> Regards,
> Daniel