[meta-freescale] mx6q: fix virtual/libgl dependencies

[Simon Braunschmidt]

Hi

I am still new to Yocto, so bear with me if some of the following
is not correct, you are welcome to open my eyes though ;-)

I have observed a problem to compile libglu in a configuration
for cgtqmx6 (imx6, from meta-fsl-arm-extra).
For a completely clean rebuild, sometimes compilation succeeds,
but sometimes it fails, not finding libGL for linking:

/home/devel/yocto/ ... /arm-poky-linux-gnueabi/4.8.1/ld: cannot find -lGL
collect2: error: ld returned 1 exit status

It looks like a race condition, sometimes the package/task providing
libGL is ready when libglu is compiled, sometimes not.

Some findings:

- meta-fsl-arm/recipes-graphics/mesa/mesa_9.1.3.bbappend is used to
  delete libGL.* after compilation of mesa

- ./recipes-graphics/gpu-viv-bin-mx6q/gpu-viv-bin-mx6q_3.0.35-4.0.0.bb, via
  gpu-viv-bin-mx6q.inc, provides its own version of libGL

- gpu-viv-bin-mx6q does not advertise "virtual/libgl" in "PROVIDES +="

- but mesa (via mesa.inc) does:
  PROVIDES = "virtual/libgl virtual/libgles1 virtual/libgles2 virtual/egl"

- so the statement in imx-base.inc
   PREFERRED_PROVIDER_virtual/libgl_mx6 ?= "gpu-viv-bin-mx6q"
  does not have effect, because mesa is still the only provider of virtual/libgl

- packages depending on virtual/libgl only get mesa, which will not contain
  the libGL library

- in fact, we still use the gl headers from mesa, but the binary blob library
  from gpu-viv-bin-mx6q (i have no words to describe this ...),
        so a package compiling against GL needs both mesa and gpu-viv-bin-mx6q

- so i suggest having gpu-viv-bin-mx6q depend on mesa to draw in the
  gl header package, advertising "virtual/libgl" for gpu-viv-bin-mx6q
  via "PROVIDES +=" and not advertising virtual/libgl for mesa via the
  .bbappend file


Would the following patch be appropriate?

Kindest Regards,
Simon
-- 
Simon Braunschmidt, emlix GmbH, http://www.emlix.com Maxfeldstraße 9,
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