libtraceevent license

Hi Greg and fellow SPDX curators 😉

One of our developers came to me with a question/complaint:

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I'm trying to use libtraceevent -- a library for parsing Linux ring buffer format.
Source code is located in the Linux kernel repository at https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/lib/traceevent 

The thing confusing me is that almost all of the files are licensed LGPL-2.1
but the Makefiles and some .c files (some of the plugins of this library),
are licensed GPL-2.0.
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Checking the sources, I find three C files:

tools/lib/traceevent/plugins/plugin_cfg80211.c
tools/lib/traceevent/plugins/plugin_scsi.c
tools/lib/traceevent/plugins/plugin_xen.c

I see that the "GPL-2.0" SPDX tag was added in commit
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b24413180f5600bcb3bb70fbed5cf186b60864bd
with the clear title:
"License cleanup: add SPDX GPL-2.0 license identifier to files with no license"
(2017-11-01, by Greg).

Shame on the original contributors for not putting license info in their files...
but I am inclined to believe that they would have been meant to be LGPL,
as the rest of the library and the other plugins.
Could it be that the "everything without a license is GPL" rule
should have exempted libtraceevent?

More importantly, shall we update the three files to be "LGPL-2.1-only" ?

-- zvr

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