[PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to provide external dtb

[PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to provide external dtb

[Manjukumar Matha]

Currently kernel-fitimage gets the dtb from KERNEL_DEVICETREE, however
there are instances when the DTB file can be generated using other
recipes, provide a way to include the DTB instead of inkernel device
tree.

Add support for external device tree during the creation of fitimage.
If virtual/dtb is set then use the path provided in
EXTERNAL_KERNEL_DEVICETREE else use KERNEL_DEVICETREE during fitimage
process

Signed-off-by: Manjukumar Matha <manjukumar.harthikote-matha@xilinx.com>
---
 meta/classes/kernel-fitimage.bbclass | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/meta/classes/kernel-fitimage.bbclass b/meta/classes/kernel-fitimage.bbclass
index 8ebd3dd..3adb1c9 100644
--- a/meta/classes/kernel-fitimage.bbclass
+++ b/meta/classes/kernel-fitimage.bbclass
@@ -30,6 +30,13 @@ python __anonymous () {
         if image:
             d.appendVarFlag('do_assemble_fitimage_initramfs', 'depends', ' ${INITRAMFS_IMAGE}:do_image_complete')
 
+	#check if there are any dtb providers
+        providerdtb = d.getVar("PREFERRED_PROVIDER_virtual/dtb")
+        if providerdtb:
+            d.appendVarFlag('do_assemble_fitimage', 'depends', ' virtual/dtb:do_populate_sysroot')
+            d.appendVarFlag('do_assemble_fitimage_initramfs', 'depends', ' virtual/dtb:do_populate_sysroot')
+            d.setVar('EXTERNAL_KERNEL_DEVICETREE', "${RECIPE_SYSROOT}/boot/devicetree")
+
         # Verified boot will sign the fitImage and append the public key to
         # U-Boot dtb. We ensure the U-Boot dtb is deployed before assembling
         # the fitImage:
@@ -373,7 +380,8 @@ fitimage_assemble() {
 	#
 	# Step 2: Prepare a DTB image section
 	#
-	if [ -n "${KERNEL_DEVICETREE}" ]; then
+
+	if [ -z "${EXTERNAL_KERNEL_DEVICETREE}" ] && [ -n "${KERNEL_DEVICETREE}" ]; then
 		dtbcount=1
 		for DTB in ${KERNEL_DEVICETREE}; do
 			if echo ${DTB} | grep -q '/dts/'; then
@@ -391,6 +399,16 @@ fitimage_assemble() {
 		done
 	fi
 
+	if [ -n "${EXTERNAL_KERNEL_DEVICETREE}" ]; then
+		dtbcount=1
+		for DTBFILE in ${EXTERNAL_KERNEL_DEVICETREE}/*.dtb; do
+			DTB=`basename ${DTBFILE}`
+			DTB=$(echo "${DTB}" | tr '/' '_')
+			DTBS="${DTBS} ${DTB}"
+			fitimage_emit_section_dtb ${1} ${DTB} ${DTBFILE}
+		done
+	fi
+
 	#
 	# Step 3: Prepare a setup section. (For x86)
 	#
-- 
2.7.4

Re: [PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to provide external dtb

[Philip Balister]

With these patches, I made a fitImage that booted on the mini-zed. It
would be nice to include a note on how to enable this. I took at few
stabs at it and ended up with

PREFERRED_PROVIDER_virtual/dtb = "devicetree"

in he machine file to get the code to trigger.

Philip

On 02/14/2019 07:56 PM, Manjukumar Matha wrote:
> Currently kernel-fitimage gets the dtb from KERNEL_DEVICETREE, however
> there are instances when the DTB file can be generated using other
> recipes, provide a way to include the DTB instead of inkernel device
> tree.
> 
> Add support for external device tree during the creation of fitimage.
> If virtual/dtb is set then use the path provided in
> EXTERNAL_KERNEL_DEVICETREE else use KERNEL_DEVICETREE during fitimage
> process
> 
> Signed-off-by: Manjukumar Matha <manjukumar.harthikote-matha@xilinx.com>
> ---
>  meta/classes/kernel-fitimage.bbclass | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/meta/classes/kernel-fitimage.bbclass b/meta/classes/kernel-fitimage.bbclass
> index 8ebd3dd..3adb1c9 100644
> --- a/meta/classes/kernel-fitimage.bbclass
> +++ b/meta/classes/kernel-fitimage.bbclass
> @@ -30,6 +30,13 @@ python __anonymous () {
>          if image:
>              d.appendVarFlag('do_assemble_fitimage_initramfs', 'depends', ' ${INITRAMFS_IMAGE}:do_image_complete')
>  
> +	#check if there are any dtb providers
> +        providerdtb = d.getVar("PREFERRED_PROVIDER_virtual/dtb")
> +        if providerdtb:
> +            d.appendVarFlag('do_assemble_fitimage', 'depends', ' virtual/dtb:do_populate_sysroot')
> +            d.appendVarFlag('do_assemble_fitimage_initramfs', 'depends', ' virtual/dtb:do_populate_sysroot')
> +            d.setVar('EXTERNAL_KERNEL_DEVICETREE', "${RECIPE_SYSROOT}/boot/devicetree")
> +
>          # Verified boot will sign the fitImage and append the public key to
>          # U-Boot dtb. We ensure the U-Boot dtb is deployed before assembling
>          # the fitImage:
> @@ -373,7 +380,8 @@ fitimage_assemble() {
>  	#
>  	# Step 2: Prepare a DTB image section
>  	#
> -	if [ -n "${KERNEL_DEVICETREE}" ]; then
> +
> +	if [ -z "${EXTERNAL_KERNEL_DEVICETREE}" ] && [ -n "${KERNEL_DEVICETREE}" ]; then
>  		dtbcount=1
>  		for DTB in ${KERNEL_DEVICETREE}; do
>  			if echo ${DTB} | grep -q '/dts/'; then
> @@ -391,6 +399,16 @@ fitimage_assemble() {
>  		done
>  	fi
>  
> +	if [ -n "${EXTERNAL_KERNEL_DEVICETREE}" ]; then
> +		dtbcount=1
> +		for DTBFILE in ${EXTERNAL_KERNEL_DEVICETREE}/*.dtb; do
> +			DTB=`basename ${DTBFILE}`
> +			DTB=$(echo "${DTB}" | tr '/' '_')
> +			DTBS="${DTBS} ${DTB}"
> +			fitimage_emit_section_dtb ${1} ${DTB} ${DTBFILE}
> +		done
> +	fi
> +
>  	#
>  	# Step 3: Prepare a setup section. (For x86)
>  	#
> 

Re: [PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to provide external dtb

[Manjukumar Harthikote Matha]

Hi Philip,

> -----Original Message-----
> From: Philip Balister [mailto:philip@balister.org]
> Sent: Sunday, February 17, 2019 3:47 PM
> To: Manjukumar Harthikote Matha <MANJUKUM@xilinx.com>
> Cc: openembedded-core <openembedded-core@lists.openembedded.org>
> Subject: Re: [OE-core][PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to
> provide external dtb
> 
> With these patches, I made a fitImage that booted on the mini-zed. It would be nice
> to include a note on how to enable this. I took at few stabs at it and ended up with

Thanks for testing it out on mini-zed

> 
> PREFERRED_PROVIDER_virtual/dtb = "devicetree"
> 

Yes, I should have added this in the commit message. I will update it and re-send V2

Thanks,
Manju

> in he machine file to get the code to trigger.
> 
> Philip
> 
> On 02/14/2019 07:56 PM, Manjukumar Matha wrote:
> > Currently kernel-fitimage gets the dtb from KERNEL_DEVICETREE, however
> > there are instances when the DTB file can be generated using other
> > recipes, provide a way to include the DTB instead of inkernel device
> > tree.
> >

<...>

Re: [PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to provide external dtb

[Richard Purdie]

On Tue, 2019-02-19 at 19:34 +0000, Manjukumar Harthikote Matha wrote:
> Hi Philip,
> 
> > -----Original Message-----
> > From: Philip Balister [mailto:philip@balister.org]
> > Sent: Sunday, February 17, 2019 3:47 PM
> > To: Manjukumar Harthikote Matha <MANJUKUM@xilinx.com>
> > Cc: openembedded-core <openembedded-core@lists.openembedded.org>
> > Subject: Re: [OE-core][PATCH 2/2] kernel-fitimage.bbclass:
> > Introduce a way to
> > provide external dtb
> > 
> > With these patches, I made a fitImage that booted on the mini-zed.
> > It would be nice
> > to include a note on how to enable this. I took at few stabs at it
> > and ended up with
> 
> Thanks for testing it out on mini-zed
> 
> > PREFERRED_PROVIDER_virtual/dtb = "devicetree"
> > 
> 
> Yes, I should have added this in the commit message. I will update it
> and re-send V2

What may also help a lot here would be some tests. This is currently a
blackhole in the tests :(


Cheers,

Richard

Re: [PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to provide external dtb

[Manjukumar Harthikote Matha]

Hi Richard,

> -----Original Message-----
> From: Richard Purdie [mailto:richard.purdie@linuxfoundation.org]
> Sent: Wednesday, February 20, 2019 3:16 PM
> To: Manjukumar Harthikote Matha <MANJUKUM@xilinx.com>; Philip Balister
> <philip@balister.org>
> Cc: openembedded-core <openembedded-core@lists.openembedded.org>
> Subject: Re: [OE-core] [PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to
> provide external dtb
> 
> On Tue, 2019-02-19 at 19:34 +0000, Manjukumar Harthikote Matha wrote:
> > Hi Philip,
> >
> > > -----Original Message-----
> > > From: Philip Balister [mailto:philip@balister.org]
> > > Sent: Sunday, February 17, 2019 3:47 PM
> > > To: Manjukumar Harthikote Matha <MANJUKUM@xilinx.com>
> > > Cc: openembedded-core <openembedded-core@lists.openembedded.org>
> > > Subject: Re: [OE-core][PATCH 2/2] kernel-fitimage.bbclass:
> > > Introduce a way to
> > > provide external dtb
> > >
> > > With these patches, I made a fitImage that booted on the mini-zed.
> > > It would be nice
> > > to include a note on how to enable this. I took at few stabs at it
> > > and ended up with
> >
> > Thanks for testing it out on mini-zed
> >
> > > PREFERRED_PROVIDER_virtual/dtb = "devicetree"
> > >
> >
> > Yes, I should have added this in the commit message. I will update it
> > and re-send V2
> 
> What may also help a lot here would be some tests. This is currently a blackhole in
> the tests :(
> 
Are there examples of having tests only for bbclass in OE-Core? 

We need a recipe or create-one to inherit this class and probably add that as a testcase. 
I am not sure how to proceed, any example would help to implement the same

Thanks,
Manju

Re: [PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to provide external dtb

[Richard Purdie]

On Thu, 2019-02-21 at 03:53 +0000, Manjukumar Harthikote Matha wrote:
> From: Richard Purdie [mailto:richard.purdie@linuxfoundation.org]
> > On Tue, 2019-02-19 at 19:34 +0000, Manjukumar Harthikote Matha
> > 
> > > > PREFERRED_PROVIDER_virtual/dtb = "devicetree"
> > > > 
> > > 
> > > Yes, I should have added this in the commit message. I will
> > > update it
> > > and re-send V2
> > 
> > What may also help a lot here would be some tests. This is
> > currently a blackhole in
> > the tests :(
> > 
> Are there examples of having tests only for bbclass in OE-Core? 

There are. See meta/lib/oeqa/selftest/cases/wic.py

I appreciate wic is a tool, not a class but the examples there should
help. You can trigger them with oe-selftest -r wic.

Another example which is a bbclass is selftest/cases/archiver.py which
does use a class inherit.

> We need a recipe or create-one to inherit this class and probably add
> that as a testcase. 
> I am not sure how to proceed, any example would help to implement the
> same

See above, they show how to add small config fragments. If you do need
a full recipe, then the meta-selftest layer of OE-Core should be able
to help too.

If you have any other questions or run into issues please do ask!

Cheers,

Richard

Re: [PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to provide external dtb

[Philip Balister]

I appreciate the nagging about testing, but I just did an update and
realized these patches never made it into master so I could request they
move into thud.

Philip

On 02/21/2019 03:37 AM, Richard Purdie wrote:
> On Thu, 2019-02-21 at 03:53 +0000, Manjukumar Harthikote Matha wrote:
>> From: Richard Purdie [mailto:richard.purdie@linuxfoundation.org]
>>> On Tue, 2019-02-19 at 19:34 +0000, Manjukumar Harthikote Matha
>>>
>>>>> PREFERRED_PROVIDER_virtual/dtb = "devicetree"
>>>>>
>>>>
>>>> Yes, I should have added this in the commit message. I will
>>>> update it
>>>> and re-send V2
>>>
>>> What may also help a lot here would be some tests. This is
>>> currently a blackhole in
>>> the tests :(
>>>
>> Are there examples of having tests only for bbclass in OE-Core? 
> 
> There are. See meta/lib/oeqa/selftest/cases/wic.py
> 
> I appreciate wic is a tool, not a class but the examples there should
> help. You can trigger them with oe-selftest -r wic.
> 
> Another example which is a bbclass is selftest/cases/archiver.py which
> does use a class inherit.
> 
>> We need a recipe or create-one to inherit this class and probably add
>> that as a testcase. 
>> I am not sure how to proceed, any example would help to implement the
>> same
> 
> See above, they show how to add small config fragments. If you do need
> a full recipe, then the meta-selftest layer of OE-Core should be able
> to help too.
> 
> If you have any other questions or run into issues please do ask!
> 
> Cheers,
> 
> Richard
> 
> 
> 
> 

Re: [PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to provide external dtb

[Manjukumar Harthikote Matha]

Hi Philip,

It was been merged in master, need to backport to Thud
https://github.com/openembedded/openembedded-core/commit/084f4de4dbaf9821516fc0254d35f4fb04311d27#diff-088b9c270c04d657c74b182de1f8e9f6

Thanks,
Manju

-----Original Message-----
From: Philip Balister [mailto:philip@balister.org] 
Sent: Wednesday, April 3, 2019 10:36 AM
To: Richard Purdie <richard.purdie@linuxfoundation.org>; Manjukumar Harthikote Matha <MANJUKUM@xilinx.com>
Cc: openembedded-core <openembedded-core@lists.openembedded.org>
Subject: Re: [OE-core] [PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to provide external dtb

I appreciate the nagging about testing, but I just did an update and realized these patches never made it into master so I could request they move into thud.

Philip

On 02/21/2019 03:37 AM, Richard Purdie wrote:
> On Thu, 2019-02-21 at 03:53 +0000, Manjukumar Harthikote Matha wrote:
>> From: Richard Purdie [mailto:richard.purdie@linuxfoundation.org]
>>> On Tue, 2019-02-19 at 19:34 +0000, Manjukumar Harthikote Matha
>>>
>>>>> PREFERRED_PROVIDER_virtual/dtb = "devicetree"
>>>>>
>>>>
>>>> Yes, I should have added this in the commit message. I will update 
>>>> it and re-send V2
>>>
>>> What may also help a lot here would be some tests. This is currently 
>>> a blackhole in the tests :(
>>>
>> Are there examples of having tests only for bbclass in OE-Core? 
> 
> There are. See meta/lib/oeqa/selftest/cases/wic.py
> 
> I appreciate wic is a tool, not a class but the examples there should 
> help. You can trigger them with oe-selftest -r wic.
> 
> Another example which is a bbclass is selftest/cases/archiver.py which 
> does use a class inherit.
> 
>> We need a recipe or create-one to inherit this class and probably add 
>> that as a testcase.
>> I am not sure how to proceed, any example would help to implement the 
>> same
> 
> See above, they show how to add small config fragments. If you do need 
> a full recipe, then the meta-selftest layer of OE-Core should be able 
> to help too.
> 
> If you have any other questions or run into issues please do ask!
> 
> Cheers,
> 
> Richard
> 
> 
> 
> 

Re: [PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to provide external dtb

[akuster808]

On 4/3/19 10:35 AM, Philip Balister wrote:
> I appreciate the nagging about testing, but I just did an update and
> realized these patches never made it into master so I could request they
> move into thud.
Thud needs testing too, its not just a master thing.

It needs to be in warrior first ; )

Either send me the master/warrior commit ids or send a patch with the
proper subject so its clear to me. 
But this looks like a new feature or am I misunderstanding?

- armin
>
> Philip
>
> On 02/21/2019 03:37 AM, Richard Purdie wrote:
>> On Thu, 2019-02-21 at 03:53 +0000, Manjukumar Harthikote Matha wrote:
>>> From: Richard Purdie [mailto:richard.purdie@linuxfoundation.org]
>>>> On Tue, 2019-02-19 at 19:34 +0000, Manjukumar Harthikote Matha
>>>>
>>>>>> PREFERRED_PROVIDER_virtual/dtb = "devicetree"
>>>>>>
>>>>> Yes, I should have added this in the commit message. I will
>>>>> update it
>>>>> and re-send V2
>>>> What may also help a lot here would be some tests. This is
>>>> currently a blackhole in
>>>> the tests :(
>>>>
>>> Are there examples of having tests only for bbclass in OE-Core? 
>> There are. See meta/lib/oeqa/selftest/cases/wic.py
>>
>> I appreciate wic is a tool, not a class but the examples there should
>> help. You can trigger them with oe-selftest -r wic.
>>
>> Another example which is a bbclass is selftest/cases/archiver.py which
>> does use a class inherit.
>>
>>> We need a recipe or create-one to inherit this class and probably add
>>> that as a testcase. 
>>> I am not sure how to proceed, any example would help to implement the
>>> same
>> See above, they show how to add small config fragments. If you do need
>> a full recipe, then the meta-selftest layer of OE-Core should be able
>> to help too.
>>
>> If you have any other questions or run into issues please do ask!
>>
>> Cheers,
>>
>> Richard
>>
>>
>>
>>

Re: [PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to provide external dtb

[Philip Balister]

On 04/03/2019 06:41 PM, Manjukumar Harthikote Matha wrote:
> Hi Philip,
> 
> It was been merged in master, need to backport to Thud
> https://github.com/openembedded/openembedded-core/commit/084f4de4dbaf9821516fc0254d35f4fb04311d27#diff-088b9c270c04d657c74b182de1f8e9f6

Yes, I was having a senior moment.

Too many projects at once :(

Philip

> 
> Thanks,
> Manju
> 
> -----Original Message-----
> From: Philip Balister [mailto:philip@balister.org] 
> Sent: Wednesday, April 3, 2019 10:36 AM
> To: Richard Purdie <richard.purdie@linuxfoundation.org>; Manjukumar Harthikote Matha <MANJUKUM@xilinx.com>
> Cc: openembedded-core <openembedded-core@lists.openembedded.org>
> Subject: Re: [OE-core] [PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to provide external dtb
> 
> I appreciate the nagging about testing, but I just did an update and realized these patches never made it into master so I could request they move into thud.
> 
> Philip
> 
> On 02/21/2019 03:37 AM, Richard Purdie wrote:
>> On Thu, 2019-02-21 at 03:53 +0000, Manjukumar Harthikote Matha wrote:
>>> From: Richard Purdie [mailto:richard.purdie@linuxfoundation.org]
>>>> On Tue, 2019-02-19 at 19:34 +0000, Manjukumar Harthikote Matha
>>>>
>>>>>> PREFERRED_PROVIDER_virtual/dtb = "devicetree"
>>>>>>
>>>>>
>>>>> Yes, I should have added this in the commit message. I will update 
>>>>> it and re-send V2
>>>>
>>>> What may also help a lot here would be some tests. This is currently 
>>>> a blackhole in the tests :(
>>>>
>>> Are there examples of having tests only for bbclass in OE-Core? 
>>
>> There are. See meta/lib/oeqa/selftest/cases/wic.py
>>
>> I appreciate wic is a tool, not a class but the examples there should 
>> help. You can trigger them with oe-selftest -r wic.
>>
>> Another example which is a bbclass is selftest/cases/archiver.py which 
>> does use a class inherit.
>>
>>> We need a recipe or create-one to inherit this class and probably add 
>>> that as a testcase.
>>> I am not sure how to proceed, any example would help to implement the 
>>> same
>>
>> See above, they show how to add small config fragments. If you do need 
>> a full recipe, then the meta-selftest layer of OE-Core should be able 
>> to help too.
>>
>> If you have any other questions or run into issues please do ask!
>>
>> Cheers,
>>
>> Richard
>>
>>
>>
>>

Re: [PATCH 2/2] kernel-fitimage.bbclass: Introduce a way to provide external dtb

[Philip Balister]

On 04/03/2019 10:12 PM, akuster808 wrote:
> 
> 
> On 4/3/19 10:35 AM, Philip Balister wrote:
>> I appreciate the nagging about testing, but I just did an update and
>> realized these patches never made it into master so I could request they
>> move into thud.
> Thud needs testing too, its not just a master thing.
> 
> It needs to be in warrior first ; )
> 
> Either send me the master/warrior commit ids or send a patch with the
> proper subject so its clear to me. 
> But this looks like a new feature or am I misunderstanding?

New feature maybe, or bugfix for meta-xilinx. Without these, people
using meta-xilinx may need to use thud + these changes.

meta-xilinx/thud needs these to build properly:

commit 084f4de4dbaf9821516fc0254d35f4fb04311d27
Author: Manjukumar Matha <manjukumar.harthikote-matha@xilinx.com>
Date:   Wed Feb 20 10:29:06 2019 -0800

    kernel-fitimage.bbclass: Introduce a way to provide external dtb

    Currently kernel-fitimage gets the dtb from KERNEL_DEVICETREE, however
    there are instances when the DTB file can be generated using other
    recipes, provide a way to include the DTB instead of inkernel device
    tree.

    Add support for external device tree during the creation of
fitimage.  If
    virtual/dtb is set using PREFERRED_PROVIDER_virtual/dtb =
"devicetree", which
    inherits the devicetree.bbclass then use the path provided in
    EXTERNAL_KERNEL_DEVICETREE else use KERNEL_DEVICETREE during
fitimage process

    Signed-off-by: Manjukumar Matha <manjukumar.harthikote-matha@xilinx.com>
    Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

ommit a7d52dbffd0da95de82d910c595a6c27d9b2ad0d
Author: Manjukumar Matha <manjukumar.harthikote-matha@xilinx.com>
Date:   Wed Feb 20 10:29:05 2019 -0800

    devicetree.bbclass: Add virtual provider for dtb

    Add virtual provider for dtb. This class can be used to generate dtb
    from static devicetree, for reference see meta-xilinx layer
    meta-xilinx/meta-xilinx-bsp/recipes-bsp/device-tree/device-tree.bb

    By providing a virtual provider we can use it to differentiate between
    in-kernel dtb or an external one. This can be set in local.conf as
    PREFERRED_PROVIDER_virtual/dtb = "devicetree"

    Signed-off-by: Manjukumar Matha <manjukumar.harthikote-matha@xilinx.com>
    Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>




> 
> - armin
>>
>> Philip
>>
>> On 02/21/2019 03:37 AM, Richard Purdie wrote:
>>> On Thu, 2019-02-21 at 03:53 +0000, Manjukumar Harthikote Matha wrote:
>>>> From: Richard Purdie [mailto:richard.purdie@linuxfoundation.org]
>>>>> On Tue, 2019-02-19 at 19:34 +0000, Manjukumar Harthikote Matha
>>>>>
>>>>>>> PREFERRED_PROVIDER_virtual/dtb = "devicetree"
>>>>>>>
>>>>>> Yes, I should have added this in the commit message. I will
>>>>>> update it
>>>>>> and re-send V2
>>>>> What may also help a lot here would be some tests. This is
>>>>> currently a blackhole in
>>>>> the tests :(
>>>>>
>>>> Are there examples of having tests only for bbclass in OE-Core? 
>>> There are. See meta/lib/oeqa/selftest/cases/wic.py
>>>
>>> I appreciate wic is a tool, not a class but the examples there should
>>> help. You can trigger them with oe-selftest -r wic.
>>>
>>> Another example which is a bbclass is selftest/cases/archiver.py which
>>> does use a class inherit.
>>>
>>>> We need a recipe or create-one to inherit this class and probably add
>>>> that as a testcase. 
>>>> I am not sure how to proceed, any example would help to implement the
>>>> same
>>> See above, they show how to add small config fragments. If you do need
>>> a full recipe, then the meta-selftest layer of OE-Core should be able
>>> to help too.
>>>
>>> If you have any other questions or run into issues please do ask!
>>>
>>> Cheers,
>>>
>>> Richard
>>>
>>>
>>>
>>>
> 
>