linux-yocto custom device tree in overlay

linux-yocto custom device tree in overlay

[Andreas Galauner]

Hi Yocto Community,

I'm currently trying to build a custom image for a beaglebone black for
which I need to enable the can-controllers on the SoC. I managed to
create an overlay which already deals with building a few tools for CAN
communication, I created a kernel config snippet for linux-yocto to
enable CAN-support in the kernel and it already works with a USB
transceiver.

Now I need to modify the device tree for the board to enable the SoC
controllers. How do I put the device tree into my overlay? I tried
several ways, but the kernel buildsystem doesn't seem to find the dts
file to be compiled.

That definitely doesn't work:
> SRC_URI += "file://can.cfg \
>             file://am335x-boneblack-cansniff.dts"
> KERNEL_DEVICETREE = "am335x-boneblack-cansniff.dtb"

Any ideas? Google wasn't too fruitful either.
With non-yocto kernels I always put the device tree into the whole path
like 'git/arch/arm/boot/dts/mydevicetree.dts'  but that also doesn't
seem to work on linux-yocto because it uses another layout in its
working directory.

I'd rather not want to create my own git repo for linux-yocto like I did
for another project where I needed the same.

Thanks for your help,
- Andy

Re: linux-yocto custom device tree in overlay

[Bruce Ashfield]

On 14-05-07 11:33 AM, Andreas Galauner wrote:
> Hi Yocto Community,
>
> I'm currently trying to build a custom image for a beaglebone black for
> which I need to enable the can-controllers on the SoC. I managed to
> create an overlay which already deals with building a few tools for CAN
> communication, I created a kernel config snippet for linux-yocto to
> enable CAN-support in the kernel and it already works with a USB
> transceiver.
>
> Now I need to modify the device tree for the board to enable the SoC
> controllers. How do I put the device tree into my overlay? I tried
> several ways, but the kernel buildsystem doesn't seem to find the dts
> file to be compiled.
>
> That definitely doesn't work:
>> SRC_URI += "file://can.cfg \
>>              file://am335x-boneblack-cansniff.dts"
>> KERNEL_DEVICETREE = "am335x-boneblack-cansniff.dtb"
>
> Any ideas? Google wasn't too fruitful either.
> With non-yocto kernels I always put the device tree into the whole path
> like 'git/arch/arm/boot/dts/mydevicetree.dts'  but that also doesn't
> seem to work on linux-yocto because it uses another layout in its
> working directory.

I use device trees all the time with linux-yocto based kernels, and
what you have above is fundamentally correct, except (as you noted)
the dts is going only be in ${WORKDIR} and not somewhere the kernel
build can find it.

So you can either patch it into the kernel, or do a bbappend with
that copies it into the source tree 
(linux/arch/arm/boot/dts/mydevicetree.dts).

Cheers,

Bruce

>
> I'd rather not want to create my own git repo for linux-yocto like I did
> for another project where I needed the same.
>
> Thanks for your help,
> - Andy
>

Re: linux-yocto custom device tree in overlay

[Andreas Galauner]

On 07/05/14 21:37, Bruce Ashfield wrote:
> So you can either patch it into the kernel, or do a bbappend with
> that copies it into the source tree
> (linux/arch/arm/boot/dts/mydevicetree.dts).

Thx! That worked fine.

For reference, this is what I added:
> do_install_prepend() {
> 	cp ${WORKDIR}/*.dts ${WORKDIR}/linux/arch/${ARCH}/boot/dts/
> }

Cheers,
- Andy

Re: linux-yocto custom device tree in overlay

[Bruce Ashfield]

On 14-05-08 09:48 AM, Andreas Galauner wrote:
> On 07/05/14 21:37, Bruce Ashfield wrote:
>> So you can either patch it into the kernel, or do a bbappend with
>> that copies it into the source tree
>> (linux/arch/arm/boot/dts/mydevicetree.dts).
>
> Thx! That worked fine.

Glad to hear!

Bruce

>
> For reference, this is what I added:
>> do_install_prepend() {
>> 	cp ${WORKDIR}/*.dts ${WORKDIR}/linux/arch/${ARCH}/boot/dts/
>> }
>
> Cheers,
> - Andy
>

Re: linux-yocto custom device tree in overlay

[adnan]

Bruce Ashfield <bruce.ashfield@...> writes:

> 
> On 14-05-08 09:48 AM, Andreas Galauner wrote:
> > On 07/05/14 21:37, Bruce Ashfield wrote:
> >> So you can either patch it into the kernel, or do a bbappend with
> >> that copies it into the source tree
> >> (linux/arch/arm/boot/dts/mydevicetree.dts).
> >
> > Thx! That worked fine.
> 
> Glad to hear!
> 
> Bruce
> 
> >
> > For reference, this is what I added:
> >> do_install_prepend() {
> >> 	cp ${WORKDIR}/*.dts ${WORKDIR}/linux/arch/${ARCH}/boot/dts/
> >> }
> >
> > Cheers,
> > - Andy
> >
> 


Hi,
I am running into the same problem. Editing the existing dts files in 
the kernel source directory does not help. After some time, the files 
are restored again.

I added my own dts file which is located at a different location but the 
method you mentioned is not clear to me. Could you please specify where 
did you add this? In which file?

Thanks in advance.
Adnan