[meta-ti] curious about libdrm-2.4.41 recipe from meta-ti layer

[Denys Dmytriyenko]

On Fri, Jul 18, 2014 at 07:46:36AM -0400, Robert P. J. Day wrote:
> 
>   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.

You missed line #11 with custom SRC_URI, which points to a forked and 
modified sources of a very specific version of libdrm for one platform.

That's why it sets COMPATIBLE_MACHINE and DEFAULT_PREFERENCE - it needs to be 
requested specifically and not selected automatically by accident. By default 
we want to use the latest upstream version from oe-core.

And it cannot be made as a bbappend - it provides a different version than 
oe-core. But it reuses GNU_SOURCE_definition.patch from oe-core, hence 
FILESEXTRAPATHS mangling.

Don't ask why it's done with forked git sources instead of patches though - 
not my decision :)

-- 
Denys