[Openembedded-architecture] Heterogeneous System Proposal

[Richard Purdie]

On Mon, 2019-12-02 at 21:58 +0000, Richard Purdie wrote:
> On Mon, 2019-12-02 at 15:37 -0600, Mark Hatle wrote:
> > In all of the above examples, the user has manually configured the
> > multiconfig within their project.  There is a simple way to move
> > that
> > configuration to a layer, simply place it in a conf/multiconfig
> > directory within that layer.
> > 
> > This ability suggests to be that there should be a standard way to
> > specify a layer above that of machine, which defines the overall
> > characteristics of the system.
> > 
> > I'm proposing calling this new layer type as a system layer and
> > it's
> > configuration variable "SYSTEM".  It will be used instead of
> > MACHINE
> > when there is no single machine to quantify the contents of the
> > produced system image.  When implementing a system, we do not want
> > to
> > make major changes to any other components.  Due to the existing
> > implementation requiring MACHINE and certain TUNE parameters, this
> > will require us to provide a special MACHINE value that can be used
> > for a heterogeneous system.  I suggest we create a new 'nomachine'
> > system that only defines/uses an equivalent noarch style
> > tune.  This
> > will instruct the system that this configuration can be used to
> > noarch software and create images (including with wic), but it is
> > not
> > able to compile specific applications.  Each of these applications
> > or
> > images must come from a defined MACHINE.
> 
> I'm not sure I 'buy' this explanation and I think a "nomachine"
> target will be horrible in practice. In your example below, why can't
> mysystem.conf just set MACHINE = "zcu_cortex-a72" and the other bits
> of linux.conf and BBMULTICONFIG = "bootloader fpga" ? 

In fact, if you create a conf/machine/system-zcu_cortex-a72.conf and
have it set something like:

BBMULTICONFIG = "bootloader fpga"
MACHINE = "zcu_cortex-a72"
require conf/machine/${MACHINE}.conf

I think what I/you describe may even work today without a new variable
and simply a new convention of a special set of new machine name
targets in layers...

Cheers,

Richard