curious about libdrm-2.4.41 recipe from meta-ti layer

["Robert P. J. Day" <rpjday@crashcourse.ca>]

  i was perusing a number of yocto layers looking for cool examples to
use in an upcoming class and ran across this oddity in the meta-ti
layer:

recipes-graphics/drm/libdrm_2.4.41.bb:
  FILESEXTRAPATHS_append := ":${COREBASE}/meta/recipes-graphics/drm/libdrm"

  in all of the layers i've looked at, that is the only example of
*appending* to FILESEXTRAPATHS i've ever seen, so i thought i'd look
closer to see what was going on.

  even though oe-core defines a libdrm recipe file, the meta-ti layer
doesn't use a bbappend for its version. rather, it explicitly adds the
libdrm/ directory from oe-core using a reference to ${COREBASE}, then
adds its own files. that's valid, i guess, it just looks weird and is
the only time i've ever seen that.

  i'm also puzzled that the meta-ti recipe sets:

DEFAULT_PREFERENCE = "-1"

what's that for?  given that the oe-core layer already defines a
recipe for libdrm that has a higher version number, why would the
above line be necessary?

  just trying to understand the rationale behind this unusual
construction.

rday

-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
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