Re: [PATCH v2 5/8] Provide include file for easy custom kernel builds

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2018-02-09 20:04, Henning Schild wrote:
> Am Fri, 9 Feb 2018 18:54:12 +0100
> schrieb Jan Kiszka <jan.kiszka@siemens.com>:
> 
>> On 2018-02-09 18:30, Henning Schild wrote:
>>> Am Thu, 8 Feb 2018 18:22:56 +0100
>>> schrieb "[ext] Jan Kiszka" <jan.kiszka@siemens.com>:
>>>   
>>>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>>>
>>>> With this include file, it becomes almost trivial to replace the
>>>> distro kernel with a custom build. You just need to include
>>>> linux-custom.inc, specify the source URI, define via S where the
>>>> source is unpacked to and provide a defconfig. To switch to a
>>>> custom kernel recipe, PREFERRED_PROVIDER_virtual/kernel has to be
>>>> adjusted in local.conf or the distro conf.
>>>>
>>>> The approach works internally by first running "make deb-pkg" on
>>>> the kernel and the repackages the output to make the binary
>>>> linux-image and linux-header debs act as replacement of their
>>>> distro packages. This results in a suboptimal technical
>>>> implementation which may eventually be replaced by an
>>>> isar-implemented deb-pkg build process. However, this is not
>>>> expected to affect the user-visible interface of this include file.
>>>>
>>>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>>>> ---
>>>>  meta/recipes-kernel/linux/linux-custom.inc | 98
>>>> ++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+)
>>>>  create mode 100644 meta/recipes-kernel/linux/linux-custom.inc
>>>>
>>>> diff --git a/meta/recipes-kernel/linux/linux-custom.inc
>>>> b/meta/recipes-kernel/linux/linux-custom.inc new file mode 100644
>>>> index 0000000..feb96a1
>>>> --- /dev/null
>>>> +++ b/meta/recipes-kernel/linux/linux-custom.inc
>>>> @@ -0,0 +1,98 @@
>>>> +# Custom kernel recipe include
>>>> +#
>>>> +# This software is a part of ISAR.
>>>> +# Copyright (c) Siemens AG, 2018
>>>> +#
>>>> +# SPDX-License-Identifier: MIT
>>>> +
>>>> +DESCRIPTION ?= "Custom kernel"
>>>> +PROVIDES = "virtual/kernel"
>>>> +
>>>> +inherit dpkg-base
>>>> +
>>>> +KERNEL_DEBIAN_DEPENDS = "initramfs-tools | linux-initramfs-tool,
>>>> kmod, linux-base (>= 4.3~)" +KERNEL_HEADERS_DEBIAN_DEPENDS =
>>>> "libc6, libssl1.1, gcc" +KBUILD_DEPENDS = "libssl-dev libelf-dev
>>>> bc"  
>>>
>>> These guys and the repacking are here because someone wrote a
>>> build-script that does not allow customization, how about not
>>> repeating that mistake and using "?=".  
>>
>> As this is an include, you can already easily adjust after including.
>> Granted, defining those as default assignment would permit
>> project-wide overrides in local.conf & Co. OK, will send v3.
> 
> Maybe i missed that so far, but could you explain why this is an
> include and not a bbclass. Not that i prefer one over the other but so
> far we do not seem to use .incs in Isar.

I have no preference either. When I started this, I looked at
linux-yocto, and that was an include at the top level. If you dig
deeper, there are also kernel classes in OE.

I still have a hard time finding differences between both extension
methods. The only difference I see right now is that "inherit
linux-kernel" would be shorter than "require
recipes-kernel/linux/linux-custom.inc"...

Anyway, I've remodeled this as class and will send out v3 soon. The
module should stay an include as it comes with additional files.

Jan

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