> > I dont think there were further discussions. > The proof of concept layer is http://layers.openembedded.org/layerindex/branch/master/layer/meta-exotic/ - https://github.com/peteasa/meta-exotic/wiki. I created a set of cross compilers for the Epiphany processor http://www.adapteva.com/epiphanyiii/ using this layer and the layer https://github.com/peteasa/meta-epiphany that builds the specific cross compilers for that processor. It worked quite well with yocto-1.7.1 so it's quite an old bit of code, however the ideas could work in a more recent versions of Yocto.
In summary the yocto-1.7.1 code had three variables of interest - BUILD: for example the system of the build machine; HOST: for example the host system on which the executable will run; TARGET: for example the system that the compiler output will be created for. The meta-exotic layer introduces a fourth EXOTIC_TARGET and this allows us to differentiate between the build machine, host system and the system that the compiled Linux kernel runs on. I called it EXOTIC because if the compiled Linux kernel and applications needs to communicate with a remote accelerator with a different system then as far as most of the Yocto build is concerned this fourth system is foreign to the embedded product (ie exotic) that the Linux kernel and applications are built on. I call it a proof of concept because at the time it seemed to me that the sensible "fix" would be to introduce these four macro's into Yocto itself so that Yocto had 4 rather than 3 selectable system (build machine, host machine, target machine and exotic machine). In the absence of full Yocto support for these 4 I used the Yocto parser rules to update the --target, --host variables in cross compilers to match the appropriate specification. See https://github.com/peteasa/meta-exotic/wiki/Introducing-EXOTIC-defines for a more detailed discussion with examples. I know that Yocto has moved on a lot since I produced the EXOTIC layer so if there is a good way to handle the creation of the various cross compilers that that is a good thing. In my case my Exotic target allowed me to create both code that ran directly on the Epiphany processor (an accelerator attached to the arm-poky-linux-gnueabi embedded system) and a cross compiler environment that allowed me to build code for both the Epiphany accelerator and the arm-poky-linux-gnueabi embedded system from the same SDK running on the SDK machine of my choice. Use of the four variables allowed me to make gcc / applications for any of the following combinations: --host=build_machine --target=build_machine --host=build_machine --target=SDK_machine --host=arm_target --target=arm_target --host=SDK_machine --target=arm_target --host=build_machine --target=Epiphany_accelerator --host=SDK_machine --target=Epiphany_accelerator --host=arm_target --target= Epiphany_accelerator Yes it complex, but these are the necessary combinations if you want to create a complete system that provides support for an embedded product with an accelerator and provides an SDK environment so that you can build locally and then download the binary to the embedded systems. All I can say is it worked for me!
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