[yocto] One kernel tree, two BSP layers, two defconfigs. How to pickup the right one based on MACHINE value?

[Paul Eggleton]

On Tue, 01 Dec 2015 11:27:19 Daniel. wrote:
> Hi Saul, thanks for your reply
> 
> 2015-11-30 21:29 GMT-02:00 Saul Wold <saul.wold at intel.com>:
> > On Mon, 2015-11-30 at 17:25 -0200, Daniel. wrote:
> >> Hi,
> >> 
> >> I have one kernel tree where I keep all my modules in-tree. Inside
> >> kernel I have two FOO_defconfig and BAR_defconfig which are
> >> configurations for FOO-board and BAR-board. On Yocto I have
> >> core-layer, FOO-bsp layer and BAR-bsp layer. At core-layer I have
> >> linux-custom.bb file which has the URI for kernel tree with a dummy
> >> defconfig. At FOO-bsp and BAR-bsp a have a .bbappend that adds a
> >> folder with the right defconfig for each board.
> >> 
> >> My doubt is: I have two .bbappends, on two distinct layers being
> >> applied at same time? Both layers are pointed at
> >> build/conf/bblayers.conf.
> > 
> > So you are including both your BSP Layers in the bblayers, that will
> > probably cause problems based on your description above.
> > 
> > Another option is to look at using overrides and have 1 layer that
> > supports both boards if they are similar and share other items.
> > 
> >> How can I have sure to pick up the right defconfig at build time?
> >> 
> >> I've tried to delete core-layer and have two kernel recipes with
> >> distinct names, but Yocto complains about two recipes being selected
> >> at same time for build (because of virtual/kernel feature or
> >> something
> >> alike). So I want to keep one kernel recipe and select the right
> >> defconfig based on MACHINE value.
> > 
> > You can use PREFERRED_PROVIDER_virtual/kernel to have multiple
> > alternate kernel present and set it in your <machine>.conf to select
> > the kernel you want.
> > 
> > If your kernel recipe does not inherit kernel.bbclass you will need to
> > set PROVIDES
> > 
> > You should also be sure to set COMPATIBLE_MACHINE for each machine
> > 
> >> Both defconfig are present on arch/arm/configs. Can I overwrite
> >> do_config()? Is that safe? About the .bbappends: Should be two
> >> .bbappends on same .bb file be avoided?
> > 
> > You can use a do_config_prepend() to deal with moving the correct
> > defconfig.
> 
> Yeah I'm doing that. As you suggested I removed the .bbappend files and
> have one recipe that support both machines, the config prepend looks
> like this:
> 
> do_configure_prepend() {
>     case "${MACHINE}" in
>         enlace-imx6)
>         bbnote "Using csi_enlace_imx6_defconfig"
>         cp -v ${S}/arch/arm/configs/csi_enlace_imx6_defconfig ${S}/defconfig
> ;;
>     pharosserver-imx6)
>             bbnote "Using csi_pharosserver_imx6_defconfig"
>         cp -v ${S}/arch/arm/configs/csi_pharosserver_imx6_defconfig
> ${S}/defconfig
>         ;;
>     esac
> }

We do already have functionality that avoids the need for custom scripting 
like this.

Unless you really need the defconfigs in-tree, the typical way to achieve this 
is to add "file://defconfig" to SRC_URI, then have defconfig files for each of the 
machines under subdirectories named the same as the machine. So your directory 
structure would look like this:

.../recipes-linux/linux-something/linux-something_versionnumber.bb
.../recipes-linux/linux-something/linux-something/enlace-imx6/defconfig
.../recipes-linux/linux-something/linux-something/pharosserver-imx6/defconfig

Cheers,
Paul

-- 

Paul Eggleton
Intel Open Source Technology Centre