Re: [PATCH] linux-custom: support to add linux-libc-dev package with kernel name

[Arulpandiyan Vadivel <arulcse2008@gmail.com>]

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On Thursday, 11 September 2025 at 10:41:19 UTC+5:30 Jan Kiszka wrote:

On 10.09.25 19:22, 'Jan Kiszka' via isar-users wrote: 
> On 10.09.25 15:55, 'Jan Kiszka' via isar-users wrote: 
>> On 21.01.25 10:47, 'Arulpandiyan Vadivel' via isar-users wrote: 
>>> Debian and Ubuntu use unified kernel headers and a single 
linux-libc-dev 
>>> package is shipped. In contrast, Isar may build multiple kernel 
variants 
>>> with different versions and/or patches and their packages but 
linux-libc-dev 
>>> are suffixed with -${KERNEL_NAME_PROVIDED}: this allows 
>>> each variant to exist in isar-apt (reprepro may not have more than one 
>>> version of a given package for a given suite). 
>>> Apply the same suffix to linux-libc-dev / 
linux-libc-dev-${DISTRO_ARCH}-cross 
>>> and a Provides: clause. 
>>> 
>>> Signed-off-by: Arulpandiyan Vadivel <arulpandiy...@siemens.com> 
>>> 
>>> --- 
>>> Changes since v4 
>>> - Updated KERNEL_PKG_LIBC_HEADERS path with KERNEL_NAME_PROVIDED 
>>> 
>>> Changes since v3 
>>> - Updated commit message to include cross packages 
>>> - updated doc/custom_kernel.md documentation 
>>> 
>>> Changes since v2 
>>> - Updated commit message as suggested 
>>> - Added KERNEL_NAME_PROVIDED for cross packages of linux-libc-dev as 
well 
>>> 
>>> --- 
>>> --- 
>>> RECIPE-API-CHANGELOG.md | 12 ++++++++++++ 
>>> doc/custom_kernel.md | 4 ++-- 
>>> meta/recipes-kernel/linux/files/debian/control.tmpl | 10 +++++++--- 
>>> .../linux/files/debian/isar/common.tmpl | 2 +- 
>>> .../linux/files/debian/isar/install.tmpl | 2 +- 
>>> meta/recipes-kernel/linux/linux-custom.inc | 2 ++ 
>>> 6 files changed, 25 insertions(+), 7 deletions(-) 
>>> 
>>> diff --git a/RECIPE-API-CHANGELOG.md b/RECIPE-API-CHANGELOG.md 
>>> index f310553a..64c0f34a 100644 
>>> --- a/RECIPE-API-CHANGELOG.md 
>>> +++ b/RECIPE-API-CHANGELOG.md 
>>> @@ -702,3 +702,15 @@ enable cross-compilation. Otherwize 
ISAR_CROSS_COMPILE = "0" now should be set 
>>> in local.conf to disable cross-compilation for all the recipes. 
>>> Sample local.conf from meta-isar used by isar-init-build-env is also 
changed 
>>> to enable cross-compilation by default. 
>>> + 
>>> +### Enable linux-libc-dev package with KERNEL_NAME 
>>> + 
>>> +By default linux-libc-dev and linux-libc-dev-${DISTRO_ARCH}-cross 
package 
>>> +was generated for architecture it builds for. 
>>> + 
>>> +This change helps to generate the `linux-libc-dev-${KERNEL_NAME}` and 
>>> +`linux-libc-dev-${DISTRO_ARCH}-cross-${KERNEL_NAME}`. 
>>> +For example, If `KERNEL_NAME` is configured as `foo` for arm64, now 
>>> +`linux-libc-dev-foo` and `linux-libc-dev-arm64-cross-foo` package will 
be 
>>> +generated. This will help to have multiple versions of linux-libc-dev 
packages 
>>> +available for respective bsps in apt feeds. 
>>> diff --git a/doc/custom_kernel.md b/doc/custom_kernel.md 
>>> index ce5f1bf7..2dca577c 100644 
>>> --- a/doc/custom_kernel.md 
>>> +++ b/doc/custom_kernel.md 
>>> @@ -51,9 +51,9 @@ The linux-custom recipe provides support for: 
>>> 
>>> Only the `host` specific package is built automatically at cross 
builds. 
>>> 
>>> - 10. Produce a `linux-libc-dev` package to support user-land builds 
>>> + 10. Produce a `linux-libc-dev-${KERNEL_NAME}` package to support 
user-land builds 
>>> 
>>> - 11. Only build/ship the `linux-libc-dev` package if instructed to 
>>> + 11. Only build/ship the `linux-libc-dev-${KERNEL_NAME}` package if 
instructed to 
>>> (`KERNEL_LIBC_DEV_DEPLOY` equals to `"1"`) 
>>> 
>>> 12. Support both native and cross compiles (`ISAR_CROSS_COMPILE`) 
>>> diff --git a/meta/recipes-kernel/linux/files/debian/control.tmpl 
b/meta/recipes-kernel/linux/files/debian/control.tmpl 
>>> index ec0da1ab..a79b86c4 100644 
>>> --- a/meta/recipes-kernel/linux/files/debian/control.tmpl 
>>> +++ b/meta/recipes-kernel/linux/files/debian/control.tmpl 
>>> @@ -22,19 +22,23 @@ Description: ${KERNEL_NAME_PROVIDED} Linux kernel 
headers for @KR@ 
>>> . 
>>> This is useful for people who need to build external modules 
>>> 
>>> -Package: linux-libc-dev 
>>> +Package: linux-libc-dev-${KERNEL_NAME_PROVIDED} 
>>> Build-Profiles: <!nolibcdev kernel> 
>>> Section: devel 
>>> -Provides: linux-kernel-headers 
>>> +Conflicts: linux-libc-dev 
>>> +Provides: linux-libc-dev 
>>> +Replaces: linux-libc-dev 
>>> Architecture: ${KERNEL_LIBC_DEV_ARCH} 
>>> Description: Linux support headers for userspace development 
>>> This package provides userspaces headers from the Linux kernel. These 
headers 
>>> are used by the installed headers for GNU glibc and other system 
libraries. 
>>> 
>>> -Package: linux-libc-dev-${DISTRO_ARCH}-cross 
>>> +Package: linux-libc-dev-${DISTRO_ARCH}-cross-${KERNEL_NAME_PROVIDED} 
>>> Build-Profiles: <!nolibcdev cross !kbuild> 
>>> Section: devel 
>>> +Conflicts: linux-kernel-headers-${DISTRO_ARCH}-cross 
>>> Provides: linux-kernel-headers-${DISTRO_ARCH}-cross 
>>> +Replaces: linux-kernel-headers-${DISTRO_ARCH}-cross 
> 
> This was also wrong. 
> 
>>> Architecture: all 
>>> Description: Linux Kernel Headers for development (for cross-compiling) 
>>> This package provides headers from the Linux kernel. These headers 
>>> diff --git a/meta/recipes-kernel/linux/files/debian/isar/common.tmpl 
b/meta/recipes-kernel/linux/files/debian/isar/common.tmpl 
>>> index f9cc2f02..b004214f 100644 
>>> --- a/meta/recipes-kernel/linux/files/debian/isar/common.tmpl 
>>> +++ b/meta/recipes-kernel/linux/files/debian/isar/common.tmpl 
>>> @@ -8,7 +8,7 @@ set -e 
>>> ARCH=${KERNEL_ARCH} 
>>> KERNEL_PKG_IMAGE=linux-image-${KERNEL_NAME_PROVIDED} 
>>> KERNEL_PKG_KERN_HEADERS=linux-headers-${KERNEL_NAME_PROVIDED} 
>>> -KERNEL_PKG_LIBC_HEADERS=linux-libc-dev 
>>> +KERNEL_PKG_LIBC_HEADERS=linux-libc-dev-${KERNEL_NAME_PROVIDED} 
>>> KERNEL_PKG_LIBC_HEADERS_CROSS=linux-libc-dev-${DISTRO_ARCH}-cross 
>> 
>> This broke the cross libc-dev package. Fix is being tested. 
>> 
>> Seems we are lacking tests for this scenario: found via xenomai-images 
>> only, and there we were lacking CI for the affected path as well :(. 
>> 
> 
> There is another issue with this patch which was likely hard to predict: 
> It broke automatic downgrades, possibly also updates, of libc-dev in the 
> sbuild-chroots. As xenomai-images is currently broken in other regards 
> as well, I cannot easily point to a demo case, but I reproduced that 
> locally: After reverting this change, I can build libevl, which really 
> needs the custom kernel's libc-dev because of extra headers, without any 
> extra dependency. 
> 
> [...] 
> Reading package lists... 
> Building dependency tree... 
> Reading state information... 
> Calculating upgrade... 
> The following packages will be upgraded: 
> linux-libc-dev 
> 1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. 
> [...] 
> 
> With this change, I would now have to add the explicit Build-Depends on 
> linux-libc-dev-${KERNEL_NAME} or the corresponding cross package. That 
> is a very ugly recipe API change that was also not documented. 
> 
> So, I'm not very happy with having this pattern here by default and 
> would prefer only using it if there are actually multiple kernels that 
> also deploy their libc-dev packages. 
> 
> Unless someone has a good idea quickly, we should revert this first and 
> retry later. 
> 

This is a design challenge: Do we really need per-KERNEL_NAME 
linux-libc-dev packages, or is it enough to tell the users to enable 
KERNEL_LIBC_DEV_DEPLOY only for one of them? 

When a single apt feeds to support multiple BSP's with same or different 
architecture for a linux-libc-dev package, without this change we may not 
be able to support them.

I think that in way of 90% of the use cases the latter will be enough 
because the kernels only differ in configuration or in patches that do 
not create conflicting changes to the UAPI headers. But can someone 
think of a case where this is not enough? 


Yes. I agree UAPI headers might be common in 99% cases unless we have 
specific BSP changes pushed and maintained

Jan 

-- 
Siemens AG, Foundational Technologies 
Linux Expert Center 

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