Guix,

The following patches add the VA-API back end for Intel GEN chips 
as well as libva-utils (which provides vainfo amongst many other 
things).  I've tested them on my Ivy Bridge laptop and they work 
wonderfully.

However.

libva (I guess) searches for the back end in mesa's store output 
by default:

--8<---------------cut here---------------start------------->8---
vainfo 
libva info: VA-API version 1.4.1
libva info: va_getDriverName() returns 0
libva info: Trying to open 
/gnu/store/clhrbkacyrclwzkzdj2ql8y572whwjzi-mesa-19.1.1/lib/dri/i965_drv_video.so
libva info: va_openDriver() returns -1
vaInitialize failed with error code -1 (unknown libva error),exit
--8<---------------cut here---------------end--------------->8---

I don't know enough about libva or mesa to know how all this can 
be made to compose nicely.

I just tested and enjoyed VA-API acceleration by (icky icky boo 
boo) copying intel-vaapi-driver's library to the mesa store 
directory, so I need help in more ways than one.

Kind regards,

T G-R