[linux-yocto] yocto-layer vs bsp-layer : criteria of choice of approach toward a custom image

[Darren Hart]

From:  New B <newbnz at yahoo.com>
Date:  Monday, March 31, 2014 at 16:27
To:  linux-yocto <linux-yocto at yoctoproject.org>
Subject:  [linux-yocto] yocto-layer vs bsp-layer : criteria of choice of
approach toward a custom image


>Hi,
>
>I am v new to yocto; read most of the doc'n and skimmed through the rest.
> I git cloned the dora branch, tag yocto 1.5.1 final
>
>Here are my questions:
>
>1- how come yocto-bsp tool wont work except when invoked within the
>poky/build dir  though e doc'n implies that new layers should be at the
>top level within the source directory?  Does it even make sense to create
>the bsp layer in a disposable directory that is not part of the repo?

Yocto-bsp depends on the source dir to create the new layer. Once created,
you can (should) move the generated layer to a location of your choosing,
get it under revision control, etc. No, it doesn't make sense to leave it
where it is generated.

>
>2- ditto for hob?

Hob uses bitbake, so also requires the proper environment to be setup.

>
>My task is to build an arm8 linux image, where the specific board has not
>yet been designed (because of stuff i signed, i can only share that the
>image is being used as an element into modeling what the board should
>look like).  So:
>3- how do you decide the approach you take in building custom image?
>      A- Do i build a64-bit arm8 linux distro using "yocto-layer create"
>and add within it a conf/machine?  Example?
>      B- Do i build a64-bit arm8 bsp layer using "yocto-bsp create" and
>add within it a conf/recipes-kernel ? Example?

Depends on what you want to add. Anything with an _MACHINEOVERRIDE or a
files/MACHINE should be in a BSP layer. Anything else belongs in a
separate layer. It will work regardless, but this is the guideline for
Yocto Project Compatibility. Whether or not you need a new BSP depends of
course on whether or not one already exists that works for your device. If
you want to change something in the MACHINE.conf, you basically want a new
BSP.

Recipes don't go under conf, see meta-intel or another BSP layer for
examples of where to add kernel recipes. (typically under the top level
meta layer /recipes-kernel/linux/linux-*.bb).


--
Darren Hart
Yocto Project - Linux Kernel
Intel Open Source Technology Center