Re: [meta-raspberrypi] Adding an additional device tree overlay in the SDCard

["Petter Mabäcker" <petter@technux.se>]

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Hi,

BR,
Petter

On 08/01/2015 03:22 AM, Herve Jourdain wrote:
>
> Hi Petter,
>
> Thanks for your answers.
>
> At some point, I’ve set it in the disto.conf – it works there – but 
> for maintenance reasons I’d love to be able to keep it “localized” 
> with the kernel .bbappend – since it clearly depends on the kernel.
>
> For now, I’ve just patched the sdcard_image-rpi.bbclass, to take the 
> existing ${KERNEL_IMAGE}*.dtb in the ${DEPLOY_DIR_DIRECTORY}, split 
> them in overlay and non-overlay, and then do the processing like it’s 
> done now.
>
> It does work in my case, and I can provide the patch if it’s deemed of 
> interest. But I’m not sure whether or not there can be some side 
> effects – looks like rather safe, but more opinions are definitely 
> needed on that.
>
Feel free to either send a RFC patch to the mailinglist or start by 
sending it for early feedback to me, Andrei and Alex.
>
> Regarding the kernel, yes I’m using the 3.18 that is supported by the 
> meta-raspberry layer. As I mentioned in another thread, with more 
> recent kernels, the RaspberryPi overlay layers were added in a 
> separate directory, so in addition to a patch to build the newer 
> kernel, the sdcard_image-rpi.bbclass will also have to be modified to 
> get the files in the proper directory, when we switch to those newer 
> kernels.
>
I remember that thread. We are currently working with integrating 4.x 
into meta-raspberrypi you can follow Alex work at 
http://redmine.gherzan.com/issues/62. One problem is however how to 
handle support for both 3.x and 4.x with the current KERNEL_DEVICETREE 
solution in combination with the changed overlay directories.
>
> Best regards,
>
> Herve
>
> *From:*Petter Mabäcker [mailto:petter@technux.se]
> *Sent:* vendredi 31 juillet 2015 15:29
> *To:* Herve Jourdain <herve.jourdain@neuf.fr>; 
> francois@concept-embarque.fr; Andrei Gherzan <andrei@gherzan.ro>
> *Cc:* yocto@yoctoproject.org
> *Subject:* Re: [yocto] [meta-raspberrypi] Adding an additional device 
> tree overlay in the SDCard
>
> Hi Herve,
>
> See inline answers.
>
> BR,
> Petter
>
> On 07/30/2015 05:27 AM, Herve Jourdain wrote:
>
>     Hello,
>
>     I’m trying to add a specific .dts file to the raspberrypi.
>
>     Therefore, in my own layer, I have made a
>     linux-raspberrypi_3.%.bbappend, that applies a patch to the
>     arch/arm/boot/dts makefile to add my own layer, and a new rule
>     that copies my specific .dts file to the kernel source directory.
>
>     And, initially, I had also defined KERNEL_DEVICETREE +=
>     “myown-overlay.dtb” in there.
>
>     It definitely compiles well, installation process is smooth, I get
>     the Image-myown-overlay.dtb in tmp/deploy/raspberrypi2.
>
>     BUT when I flash my SDCard, it does NOT appear in the “overlays”
>     directory of the DOS partition!
>
>     If I add it manually, everything works fine, so I know my overlay
>     has been correctly generated and is working.
>
>     What I discovered is that, the sdcard_image_rpi class takes the
>     list of .dtb to be considered from split_overlays(), which is
>     defined in linux-raspberrypi-base class.
>
>     And split_overlays() basically  gets the value of
>     KERNEL_DEVICETREE (dts = d.getVar("KERNEL_DEVICETREE", True)).
>
>     But when I set KERNEL_DEVICETREE in
>     linux-raspberrypi_3.%.bbappend, it seems the additional value it
>     defines is NOT taken into account when linux-raspberry-class
>     evaluates the value of KERNEL_DEVICETREE.
>
>     I’ve checked in the create_image.rpi-sdimg script created, it does
>     not appear in DTS nor DT_OVERLAYS.
>
>     But when I define KERNEL_DEVICETREE in my distro.conf, THEN it is
>     taken into account…
>
>     My goal would be to add that overlay by NOT modifying distro.conf
>     (distros are not necessarily RaspberryPi centric) nor in the
>     raspberry machine files (or local.conf).
>
>     This leads me to several questions:
>
>     #1 Is there a specific reason why my addition to KERNEL_DEVICETREE
>     gets lost when creating the image? I mean, is it normal, or are
>     there some steps I missed there?
>
> Yes, in the current solution KERNEL_DEVICETREE is needed in both the 
> kernel recipe and image creation context. When appending 
> KERNEL_DEVICETREE in linux-raspberrypi_3.%.bbappend your new overlay 
> will only be visible within the linux-raspberrypi scope and NOT within 
> the image class.
>
>
>     #2 Is there a way that I could achieve adding my .dtb overlay in
>     the sdcard image only from my linux kernel bbappend?
>
>
> If I remember the code correct within the kernel scope we are only 
> interesting if device tree should be used. At least in theory 
> (assuming you are using a >= 3.18 kernel since then KERNEL_DEVICETREE 
> will bve set by default) you should be able to skip the 
> KERNEL_DEVICETREE += code in linux-raspberrypi_3.%.bbappend (since it 
> will be set any way and the overlays themselves isn't really used in 
> here..) then append the KERNEL_DEVICETREE within the image scope. If 
> you don't want to put this into the layer.conf or similiar in your own 
> layer I guess it should work to "prepend" for example the 
> IMAGE_CMD.But in the current solution I guess local.conf, layer.conf 
> (in your own layer) or rpi-base.inc (in meta-raspberrypi) is the 
> easiest options..
>
>
>     #3 On a more general note, wouldn’t it be simpler (better?) to
>     just add all the .dtb that are found in the deploy/images/
>     directory to the DOS partition of the SDCard? After all, the .dtb
>     need to be compiled from a .dts, so all the .dtb that appear in
>     deploy/images are “legit”.
>
>
> That might perhaps be a better solution. Have you tried it out? Andrei 
> or Francois might have some comments about this?
>
>     Herve
>
>
>


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