Hi

As ARM now also moved to device tree it look like in future we will have more kernels that are using device tree then ones that are not.
As far as I understand currently the generation of device trees is controlled via KERNEL_DEVICETREE and is handled in via an include file recipes-kernel/linux/linux-dtb.inc.

I was thinking about moving this include into a class so it becomes easier to use. Before I dive into implementing something I would like some feedback from the community.

I have the following variant in mind.

Add the device tree generation to the current kernel.bbclass (or let kernel.bblcass inherit from a kernel-dtb.bbclass).
This way all kernels would automatically be DT enabled.
The class would check if KERNEL_DEVICETREE is set and generate device trees based on this information. For boards that don't have KERNEL_DEVICETREE set the class would do nothing and the behavior is like before.
The advantage I see with this approach is that the only thing a user needs to do is to set KERNEL_DEVICETREE in the board and make sure the device trees are available in the kernel they like to build.

I appreciate your feedback?

Regards
Pascal

On 2015-04-15 08:33 AM, Bach, Pascal wrote:

Hi

Adding oe-core, since that's the right place to have a discussion like
this.

As ARM now also moved to device tree it look like in future we will have more kernels that are using device tree then ones that are not.

True, but it has been like this for quite some time now :)

As far as I understand currently the generation of device trees is controlled via KERNEL_DEVICETREE and is handled in via an include file recipes-kernel/linux/linux-dtb.inc.

I was thinking about moving this include into a class so it becomes easier to use. Before I dive into implementing something I would like some feedback from the community.

The big trick with changing anything like this is compatibility with
existing recipes. Whatever we do, existing recipes and layers shouldn't
be broken .. or if they are broken, there should be a compelling
technical reason to do so.

I have the following variant in mind.

Add the device tree generation to the current kernel.bbclass (or let kernel.bblcass inherit from a kernel-dtb.bbclass).
This way all kernels would automatically be DT enabled.
The class would check if KERNEL_DEVICETREE is set and generate device trees based on this information. For boards that don't have KERNEL_DEVICETREE set the class would do nothing and the behavior is like before.
The advantage I see with this approach is that the only thing a user needs to do is to set KERNEL_DEVICETREE in the board and make sure the device trees are available in the kernel they like to build.

That's pretty much the experience that most users have now, since
there's nearly always a kernel recipe created, that recipe includes
linux-dtb.inc, and sets KERNEL_DEVICETREE.

Everything else happens to build and package the device tree.

Was there something specifically that was causing issues with the
current way of building them ?

Cheers,

Bruce

I appreciate your feedback?

Regards
Pascal

Hi Bruce,

On 04/15/2015 04:13 PM, Bruce Ashfield wrote:

On 2015-04-15 08:33 AM, Bach, Pascal wrote:

Hi

Adding oe-core, since that's the right place to have a discussion
like this.

As ARM now also moved to device tree it look like in future we will
have more kernels that are using device tree then ones that are
not.

True, but it has been like this for quite some time now :)

As far as I understand currently the generation of device trees is
controlled via KERNEL_DEVICETREE and is handled in via an include
file recipes-kernel/linux/linux-dtb.inc.

I was thinking about moving this include into a class so it becomes
easier to use. Before I dive into implementing something I would
like some feedback from the community.

The big trick with changing anything like this is compatibility with
existing recipes. Whatever we do, existing recipes and layers
shouldn't be broken .. or if they are broken, there should be a
compelling technical reason to do so.

I have the following variant in mind.

Add the device tree generation to the current kernel.bbclass (or
let kernel.bblcass inherit from a kernel-dtb.bbclass). This way all
kernels would automatically be DT enabled. The class would check if
KERNEL_DEVICETREE is set and generate device trees based on this
information. For boards that don't have KERNEL_DEVICETREE set the
class would do nothing and the behavior is like before. The
advantage I see with this approach is that the only thing a user
needs to do is to set KERNEL_DEVICETREE in the board and make sure
the device trees are available in the kernel they like to build.

That's pretty much the experience that most users have now, since
there's nearly always a kernel recipe created, that recipe includes
linux-dtb.inc, and sets KERNEL_DEVICETREE.

As far as I understood, Pascal's idea is to remove the need for user
recipes to include linux-dtb.inc, and provide this functionality via
inheritance.

Everything else happens to build and package the device tree.

Was there something specifically that was causing issues with the
current way of building them ?

Cheers,

Bruce

I appreciate your feedback?

Regards Pascal

Regards,
Nikolay

On Wed, Apr 15, 2015 at 11:22 AM, Nikolay Dimitrov <picmaster@...> wrote:

Hi Bruce,


On 04/15/2015 04:13 PM, Bruce Ashfield wrote:

On 2015-04-15 08:33 AM, Bach, Pascal wrote:

Hi

Adding oe-core, since that's the right place to have a discussion
like this.

As ARM now also moved to device tree it look like in future we will
have more kernels that are using device tree then ones that are
not.

True, but it has been like this for quite some time now :)

As far as I understand currently the generation of device trees is
controlled via KERNEL_DEVICETREE and is handled in via an include
file recipes-kernel/linux/linux-dtb.inc.

I was thinking about moving this include into a class so it becomes
easier to use. Before I dive into implementing something I would
like some feedback from the community.

The big trick with changing anything like this is compatibility with
existing recipes. Whatever we do, existing recipes and layers
shouldn't be broken .. or if they are broken, there should be a
compelling technical reason to do so.

I have the following variant in mind.

Add the device tree generation to the current kernel.bbclass (or
let kernel.bblcass inherit from a kernel-dtb.bbclass). This way all
kernels would automatically be DT enabled. The class would check if
KERNEL_DEVICETREE is set and generate device trees based on this
information. For boards that don't have KERNEL_DEVICETREE set the
class would do nothing and the behavior is like before. The
advantage I see with this approach is that the only thing a user
needs to do is to set KERNEL_DEVICETREE in the board and make sure
the device trees are available in the kernel they like to build.

That's pretty much the experience that most users have now, since
there's nearly always a kernel recipe created, that recipe includes
linux-dtb.inc, and sets KERNEL_DEVICETREE.

As far as I understood, Pascal's idea is to remove the need for user
recipes to include linux-dtb.inc, and provide this functionality via
inheritance.

That is obvious. My questions are around "why". There's no big
technical advantage, and if you remove that existing file, you break
existing recipes. Which means you need to leave a stub in place.

So without a technical advantage, it's churn for the sake of
churn.

Bruce

Everything else happens to build and package the device tree.

Was there something specifically that was causing issues with the
current way of building them ?

Cheers,

Bruce

I appreciate your feedback?

Regards Pascal

Regards,
Nikolay

--
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yocto mailing list
yocto@...
https://lists.yoctoproject.org/listinfo/yocto

--
"Thou shalt not follow the NULL pointer, for chaos and madness await
thee at its end"

Hi Bruce,

On 04/15/2015 06:26 PM, Bruce Ashfield wrote:

On Wed, Apr 15, 2015 at 11:22 AM, Nikolay Dimitrov
<picmaster@...> wrote:

Hi Bruce,


On 04/15/2015 04:13 PM, Bruce Ashfield wrote:

On 2015-04-15 08:33 AM, Bach, Pascal wrote:

Hi

Adding oe-core, since that's the right place to have a discussion
like this.

As ARM now also moved to device tree it look like in future we
will have more kernels that are using device tree then ones
that are not.

True, but it has been like this for quite some time now :)

As far as I understand currently the generation of device
trees is controlled via KERNEL_DEVICETREE and is handled in via
an include file recipes-kernel/linux/linux-dtb.inc.

I was thinking about moving this include into a class so it
becomes easier to use. Before I dive into implementing
something I would like some feedback from the community.

The big trick with changing anything like this is compatibility
with existing recipes. Whatever we do, existing recipes and
layers shouldn't be broken .. or if they are broken, there
should be a compelling technical reason to do so.

I have the following variant in mind.

Add the device tree generation to the current kernel.bbclass
(or let kernel.bblcass inherit from a kernel-dtb.bbclass).
This way all kernels would automatically be DT enabled. The
class would check if KERNEL_DEVICETREE is set and generate
device trees based on this information. For boards that don't
have KERNEL_DEVICETREE set the class would do nothing and the
behavior is like before. The advantage I see with this
approach is that the only thing a user needs to do is to set
KERNEL_DEVICETREE in the board and make sure the device trees
are available in the kernel they like to build.

That's pretty much the experience that most users have now, since
there's nearly always a kernel recipe created, that recipe
includes linux-dtb.inc, and sets KERNEL_DEVICETREE.

As far as I understood, Pascal's idea is to remove the need for
user recipes to include linux-dtb.inc, and provide this
functionality via inheritance.

That is obvious. My questions are around "why". There's no big
technical advantage, and if you remove that existing file, you break
existing recipes. Which means you need to leave a stub in place.

So without a technical advantage, it's churn for the sake of churn.

Well, removing redundancy and simplifying users' recipes could be
considered an advantage. Also, as the contents of linux-dtb.inc are
going to be moved to bbclass, the file can be left empty, later
maintainers remove the extra line from all users' recipes in following
commits. I don't see breaking as an option.

Bruce

Everything else happens to build and package the device tree.

Was there something specifically that was causing issues with the
current way of building them ?

Cheers,

Bruce

I appreciate your feedback?

Regards Pascal

Kind regards,
Nikolay

On Wed, Apr 15, 2015 at 12:12 PM, Nikolay Dimitrov <picmaster@...> wrote:

Hi Bruce,


On 04/15/2015 06:26 PM, Bruce Ashfield wrote:

On Wed, Apr 15, 2015 at 11:22 AM, Nikolay Dimitrov
<picmaster@...> wrote:

Hi Bruce,


On 04/15/2015 04:13 PM, Bruce Ashfield wrote:

On 2015-04-15 08:33 AM, Bach, Pascal wrote:

Hi

Adding oe-core, since that's the right place to have a discussion
like this.

As ARM now also moved to device tree it look like in future we
will have more kernels that are using device tree then ones
that are not.

True, but it has been like this for quite some time now :)

As far as I understand currently the generation of device
trees is controlled via KERNEL_DEVICETREE and is handled in via
an include file recipes-kernel/linux/linux-dtb.inc.

I was thinking about moving this include into a class so it
becomes easier to use. Before I dive into implementing
something I would like some feedback from the community.

The big trick with changing anything like this is compatibility
with existing recipes. Whatever we do, existing recipes and
layers shouldn't be broken .. or if they are broken, there
should be a compelling technical reason to do so.

I have the following variant in mind.

Add the device tree generation to the current kernel.bbclass
(or let kernel.bblcass inherit from a kernel-dtb.bbclass).
This way all kernels would automatically be DT enabled. The
class would check if KERNEL_DEVICETREE is set and generate
device trees based on this information. For boards that don't
have KERNEL_DEVICETREE set the class would do nothing and the
behavior is like before. The advantage I see with this
approach is that the only thing a user needs to do is to set
KERNEL_DEVICETREE in the board and make sure the device trees
are available in the kernel they like to build.

That's pretty much the experience that most users have now, since
there's nearly always a kernel recipe created, that recipe
includes linux-dtb.inc, and sets KERNEL_DEVICETREE.

As far as I understood, Pascal's idea is to remove the need for
user recipes to include linux-dtb.inc, and provide this
functionality via inheritance.

That is obvious. My questions are around "why". There's no big
technical advantage, and if you remove that existing file, you break
existing recipes. Which means you need to leave a stub in place.

So without a technical advantage, it's churn for the sake of churn.

Well, removing redundancy and simplifying users' recipes could be
considered an advantage. Also, as the contents of linux-dtb.inc are
going to be moved to bbclass, the file can be left empty, later
maintainers remove the extra line from all users' recipes in following
commits. I don't see breaking as an option.

And we could argue that having more inherits in the base is a bad
thing for users that have no interest in device trees.

One person's advantage is another's churn. I was looking for technical
advantages or a plan for future features that might leverage this.

Cheers,

Bruce

Bruce

Everything else happens to build and package the device tree.

Was there something specifically that was causing issues with the
current way of building them ?

Cheers,

Bruce

I appreciate your feedback?

Regards Pascal

Kind regards,
Nikolay

--
"Thou shalt not follow the NULL pointer, for chaos and madness await
thee at its end"

Hi Bruce, Hi Nikolay

Adding oe-core, since that's the right place to have a discussion
like this.

Thanks I'm never sure where to ask what :)

As ARM now also moved to device tree it look like in future we

will

have more kernels that are using device tree then ones that are
not.

True, but it has been like this for quite some time now :)

As far as I understand currently the generation of device trees is
controlled via KERNEL_DEVICETREE and is handled in via an include
file recipes-kernel/linux/linux-dtb.inc.

I was thinking about moving this include into a class so it

becomes

easier to use. Before I dive into implementing something I would
like some feedback from the community.

The big trick with changing anything like this is compatibility

with

existing recipes. Whatever we do, existing recipes and layers
shouldn't be broken .. or if they are broken, there should be a
compelling technical reason to do so.

I have the following variant in mind.

Add the device tree generation to the current kernel.bbclass (or
let kernel.bblcass inherit from a kernel-dtb.bbclass).
This way all kernels would automatically be DT enabled. The class
would check if KERNEL_DEVICETREE is set and generate device trees
based on this information. For boards that don't have
KERNEL_DEVICETREE set the class would do nothing and the behavior
is like before. The advantage I see with this approach is that the
only thing a user needs to do is to set KERNEL_DEVICETREE in the
board and make sure the device trees are available in the kernel
they like to build.

That's pretty much the experience that most users have now, since
there's nearly always a kernel recipe created, that recipe includes
linux-dtb.inc, and sets KERNEL_DEVICETREE.

As far as I understood, Pascal's idea is to remove the need for user
recipes to include linux-dtb.inc, and provide this functionality via
inheritance.

That is obvious. My questions are around "why". There's no big
technical advantage, and if you remove that existing file, you break
existing recipes. Which means you need to leave a stub in place.

So without a technical advantage, it's churn for the sake of churn.

Well, removing redundancy and simplifying users' recipes could be
considered an advantage. Also, as the contents of linux-dtb.inc are
going to be moved to bbclass, the file can be left empty, later
maintainers remove the extra line from all users' recipes in following
commits. I don't see breaking as an option.

I completely agree that it is not worth to breaking existing recipes because of that.
But I think the option with an empty linux-dtb.inc is acceptable.

Everything else happens to build and package the device tree.

Was there something specifically that was causing issues with the
current way of building them ?

There was no specific issue except that it feels like an unnecessary includes.
And it seems a bit odd to me that most of the work of building the kernel is done in bbclasses,
while just the dtb handling is done with an include. But of course it still is more of a cosmetic
change than a real technical necessity.

Regards
Pascal